U.S. patent application number 10/975693 was filed with the patent office on 2005-04-28 for providing compressed video.
This patent application is currently assigned to WebTV Networks, Inc.. Invention is credited to Feder, Meir, Keren, Avishai, Paz, Ofir.
Application Number | 20050091692 10/975693 |
Document ID | / |
Family ID | 11062344 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050091692 |
Kind Code |
A1 |
Paz, Ofir ; et al. |
April 28, 2005 |
Providing compressed video
Abstract
A computer may be remotely accessed. At a first location,
display commands are generated. The display commands are covered
into a compressed video data stream. Each display element (5) is
checked if it is encoded (52). If object is encoded, it is
transcribed into MPEG (54). The image is adjusted for display (56)
and compression (58). Additional steps of motion determination
(60), change detection (62), compression depth and frame
determination (66, 68) are executed. Then the data is transmitted
to a second location. The display commands are decompressed and
displayed as an image at the second location.
Inventors: |
Paz, Ofir; (Rishon Lezion,
IL) ; Keren, Avishai; (Rosh Ha'Ayin, IL) ;
Feder, Meir; (Herzelia, IL) |
Correspondence
Address: |
WORKMAN NYDEGGER/MICROSOFT
1000 EAGLE GATE TOWER
60 EAST SOUTH TEMPLE
SALT LAKE CITY
UT
84111
US
|
Assignee: |
WebTV Networks, Inc.
Mountain View
CA
|
Family ID: |
11062344 |
Appl. No.: |
10/975693 |
Filed: |
October 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10975693 |
Oct 27, 2004 |
|
|
|
09770766 |
Jan 25, 2001 |
|
|
|
Current U.S.
Class: |
725/95 ; 348/564;
725/100; 725/116; 725/117; 725/146; 725/147 |
Current CPC
Class: |
H04N 19/61 20141101;
H04N 21/6187 20130101; H04N 21/234363 20130101; H04N 21/488
20130101; H04N 21/2543 20130101; H04N 21/8586 20130101; H04N 21/262
20130101; A63F 2300/577 20130101; H04N 21/233 20130101; H04N 21/478
20130101; A63F 2300/538 20130101; H04N 21/2668 20130101; H04N
21/6408 20130101; H04N 21/6587 20130101; H04N 21/23412 20130101;
H04N 21/6547 20130101; H04N 21/8173 20130101; H04N 21/2407
20130101; H04N 21/234354 20130101; H04N 21/6168 20130101; H04N
21/234381 20130101; A63F 2300/409 20130101; H04N 21/241 20130101;
H04N 19/587 20141101; H04N 21/8543 20130101; H04N 19/132 20141101;
A63F 2300/5506 20130101; H04N 21/274 20130101; H04N 21/6405
20130101; H04N 21/8453 20130101; H04N 19/124 20141101; H04N 19/134
20141101; H04N 7/165 20130101; H04N 21/234336 20130101; H04N
21/23655 20130101; H04N 21/2402 20130101; H04N 21/812 20130101 |
Class at
Publication: |
725/095 ;
348/564; 725/116; 725/117; 725/146; 725/147; 725/100 |
International
Class: |
H04N 007/173; H04N
007/16; H04N 005/445 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 1998 |
WO |
PCT/IL98/00349 |
Claims
1. A method of generating a plurality of displays, comprising:
generating a first set of display commands, by a first program;
generating at least a second set of display commands, by at least a
second program; differentially affecting said first and said second
programs, to generate said display commands; and converting each of
said first and said second sets of display commands into a
compressed video stream, wherein said differentially affecting
comprises differentially affecting to meet an instantaneous
resource limitation.
2. A method according to claim 1, wherein said resource limitation
comprises a transmission bandwidth limitation.
3. A method according to claim 1, wherein said resource limitation
comprises a limitation on CPU available to perform said
conversion.
4. A method of generating a plurality of displays, comprising:
generating a first set of display commands, by a first program;
generating at least a second set of display commands, by at least a
second program; differentially modifying said first and said sets
of display commands; and converting each of said first and said
second sets of display commands into a compressed video stream,
wherein said differentially modifying comprises differentially
modifying to meet an instantaneous resource limitation.
5. A method according to claim 4, wherein said resource limitation
comprises a transmission bandwidth limitation.
6. A method according to claim 4, wherein said resource limitation
comprises a limitation on CPU available to perform said conversion.
Description
RELATED APPLICATIONS
[0001] The present application is a divisional application of
commonly-assigned U.S. patent application Ser. No. 09/770,766 filed
Jan. 25, 2001, entitled "Providing Compressed Video" which claims
priority under 35 U.S.C. .sctn. 120 or .sctn. 365 (c) of PCT
application No. PCT/IL98/00349 entitled "Remote Computer Access"
filed Jul. 27, 1998, both of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention relates to remote operation of
computer systems and in particular to remote access to a computer
running an Internet browser.
[0004] 2. The Relevant Technology
[0005] Various methods of remotely accessing a computing server
have been used in the past. One of the first methods utilized a
server and terminals. Input is entered at the terminals,
transmitted to the server and the results are send back over data
lines to the terminals. The terminals can be "dumb" terminals, such
as a VT52, with no processing power except to display the data, or
they can be smart terminals, such as an IBM 3270, which can do some
basic form filling without requiring intervention of the
server.
[0006] As computing power has grown cheaper, various other
strategies have been used. In the X11 graphical networking
protocol, a display server sends bitmaps to a display client and
receives input events from the client In the NeWS graphical
networking protocol, a server sends short code segments to a client
computer. The code segments perform display and input handling
functions at the client and, when needed, send input to--and
receive display data from--the server.
[0007] A somewhat different type of remote computer access is
Internet-TV. A television set is upgraded using an electronic box
so that the television may be used to access the Internet. In one
system, Internet related data is transmitted to and from the
electronic box using protocols which transmit data over a cable
network.about. In some instances, the data is transmitted using a
data channel provided by an MPEG compression protocol. In one
system, the box is a computer, which performs the Internet
communication via the cable network and which uses the television
as a display. In another system, a server at a cable center, sends
graphical display commands to the box and the box generates a video
signal responsive to the commands. Typically, the display commands
are a subset of Java or HTML. In another system, the data comprises
Java scripts which are executed by the box.
[0008] Cable networks have also long been used to send video and/or
audio programs on demand to a particular subscriber. The video
programs are compressed before sending so that a wider bandwidth is
available over the cable networks. A set-top box at each subscriber
is hardwired (and/or programmed) to decompress the video program
and convert it into a video signal for the television. Such video
on demand may be a live performance or may be retrieved from an
archive. It is also possible to view video segments via the
Internet.
[0009] Generally, when video is transmitted, a same bandwidth is
allocated to a plurality of video channels. In packet based video
transmission, subscribers and/or channels that require a higher
data rate receive more packets per second than subscribers who need
a lower data rate. A company named "iMedia" uses a method of
statistical multiplexing in which bandwidth is dynamically
allocated between video channels, based on signal characteristics
of the video being transmitted. The allocation does not depend on
the content per-se of the video channels. In fact, the statistical
multiplexing is preferably affected without decompressing the
images.
[0010] Related patent publications include U.S. Pat. Nos.
5,612,742, 5,687,257 and 5,115,309 and PCT publication WO 97/12486,
the disclosures of which are incorporated herein by reference.
[0011] The following articles, "Polygon Assisted JPEG and MPEG
Compression of Synthetic Images", by Marc Levoy, Proceeding of
Siggraph 1995, "Model Based Motion Estimation for Synthetic
Animations", by Maneesh Agrawala, Andrew C. Beers and Navin
Chaddha, in ACM Multimedia 1995, and "Compression Performance of
the Xremote Protocol", by John Danskin and Pat Hanrahan,
Proceedings 1994 Data Compression Conference, the disclosures of
which are incorporated herein by reference, describe methods
compressing animation into MPEG format, on a single machine. In
these methods the compression is faster since the "video source",
the animation, is completely known.
BRIEF SUMMARY OF THE INVENTION
[0012] One object of some embodiments of the present invention is
to provide a client-server protocol which operates via a cable
network. Preferable, the server is used to connect to the Internet.
Preferably, the client comprises a television and a set-top
box.
[0013] An object of some preferred embodiments of the invention is
to provide methods of more efficiently compressing video, which
video is generated by a computer.
[0014] An object of some preferred embodiments of the invention is
to provide methods of bandwidth allocation for cable-network
systems where the data transmitted relates to computer
communications. Preferably, the computer communications comprise
compressed screen displays.
[0015] One aspect of some preferred embodiments of the present
invention relates to providing remote computer access using
compressed video. Preferably, one or more clients are connected to
a single server using a cable network. Preferably, displays are
sent from the server to the clients using compressed video,
preferably using an MPEG II compression protocol. Preferably, the
clients provide feedback to the server using data transmission over
the cable network. Alternatively, the feedback may be provided over
a telephone line.
[0016] Another aspect of some preferred embodiments of the
invention relates to efficient video compression, especially MPEG
II compression, of computer generated displays. Efficient
compression may be faster, of a higher quality and/or be obtained
using a cheaper hardware and/or software base. In one preferred
embodiment of the invention, such efficient compression is achieved
by bypassing motion estimation algorithms. Such bypassing may be
achieved by taking note of display manipulation commands and
tracking which portions of a display are changed and which are
shifted. Display manipulation commands include, for example,
scrolling commands and pan commands.
[0017] Alternatively or additionally, efficient compression is
achieved by maintaining the compression of video, audio and/or
still images which are retrieved by the server and sent to the
client, instead of decompressing them and then compressing them
again prior to sending them.
[0018] Alternatively or additionally, efficient compression is
achieved by modifying a display, which would have been used for a
user working on the server, so that it can be more efficiently
compressed.
[0019] Alternatively or additionally, efficient compression is
achieved by direct drawing of graphical elements of a display into
a DCT space, instead of--or in addition to--drawing into an image
space and then performing a transform.
[0020] Alternatively or additionally, efficient compression is
achieved by reusing portions of a display and/or a DCT space,
between images and/or between clients.
[0021] Another aspect of some preferred embodiments of the
invention relates to image processing an image and/or a video
stream. In a preferred embodiment of the invention, image
processing of an image is combined with a compression stage by
providing an image, compressing the image and image processing the
image by manipulation of compression parameters and/or by
processing of the compressed data. It should be appreciated that it
would have been possible to process the image before compressing.
However, in some cases, the image processing is more computational
efficient by processing the compressed data. In a preferred
embodiment of the invention, an image is low-pass filtered by
reducing the quantization rate of low frequency components. In a
preferred embodiment of the invention, only the vertical frequency
components are modified, to reduce flicker in a reconstructed
image. In another example a different wavelet resolution is used in
a vertical direction of an image.
[0022] Another aspect of some preferred embodiments of the
invention relates to asynchronic image compression and
transmission. In a preferred embodiment of the invention, an image
or an image portion is compressed in an asynchronic manner, for
example, depending on available bandwidth, available computational
power, indication of changes in the image, desirable image quality
and/or type of change in the image. In a preferred embodiment of
the invention, the display rate and/or the image generate rate are
unaffected by the asynchronic characteristics of the data
compression.
[0023] In a preferred embodiment of the invention, a compression
step is prompted by an event which marks a change in the image. In
a preferred embodiment of the invention, only the portions of the
image which are affected by the event are compressed. A new image
frame is created and sent to a decompression and display unit. Such
a new image frame may comprise a completely new frame or a frame
which defines changes over one or more previous frames. In a
preferred embodiment of the invention, two change events may be
combined in a single new frame. In some cases, one change event may
moot a previous change event, so that only the changes associate
with one event are processed.
[0024] In a preferred embodiment of the invention, the system may
operate at several different frame rates simultaneously: image
generation frame rate, actual compression frame rate, maximum
compression frame rate and display frame rate. In a preferred
embodiment of the invention, each of these frame rates may be
independently varied, for example, the image generation rate may
depend on a computer program which generates the image. The actual
compression rate may depend on available computing power and/or on
whether there were any changes in the frame. The maximum
compression rate may be the maximum frame rate which is allocated
for a particular user and may depend on a user request, available
bandwidth and/or payment schedule. The display rate may depend on
the characteristics of the display device, be it NTSC, PAL or HDTV.
In a preferred embodiment of the invention, the actual compression
rate and the display rate are synchronized by buffering the
actually sent frames with "no change" frames, to maintain the
display frame rate constant. In a preferred embodiment of the
invention, the maximum frame rate determines the number of frames
sent, with the balance between the maximum frame rate and the
compression frame rate also being buffered using "no change"
frames.
[0025] Alternatively or additionally, the MPEG decompression module
may be modified to work with variable frame rates.
[0026] Another aspect of some preferred embodiments of the
invention relates to bandwidth allocation between a plurality of
clients. In accordance with one preferred embodiment of the
invention, the compression depth is traded-off between the clients.
Preferably, each client is provided with a minimum bandwidth
according to his needs.
[0027] Alternatively or additionally, bandwidth is allocated by
providing each client with a different frame rate. Typically, a
25/30 Hz (changed) frame rate is not needed in any computer
application, so that a lower frame rate may generally be used for
such applications.
[0028] Alternatively or additionally the bandwidth is allocated
responsive to the amount of motion in the display for each
client.
[0029] Another aspect of some preferred embodiments of the
invention relates to adjusting the displayed information to match a
particular compression required and/or display characteristics of a
television used to display the data. In one example, a cursor
flashing rate may be changed so that a lower frame rate is
required. In another example, the colors of a displayed portion are
adjusted so that compression of color components is more efficient.
In still another example, display elements, such as bullets and
letters are moved so that they do not straddle compression-block
boundaries. In another example, a display background may be
replaced by a different display background, for example to simplify
compression or to utilize a pre-compressed background. Preferably,
the background is compared to a set of stored background portions
to determine which background is most similar. In a preferred
embodiment of the invention, if all the pre-stored backgrounds are
different by more than a threshold amount, the original background
may be used. Alternatively or additionally, the original background
may be modified to simplify compression. In a preferred embodiment
of the invention, a background is analyzed to determine if it is
unique and should not be replaced. Such an analysis may include,
inter alia, analyzing the size of the background image, analyzing
the contrast and/or analyzing the colors of the image. Generally, a
garish, large and/or high--contrast background is a unique
background. Plain, simple and low-contrast backgrounds are
generally "standard" and replaceable backgrounds. Preferably, when
determining which background to replace the original background
with, a plurality of parameters of the original background are used
to select a match. Such parameters can include main color (a
replacement background can be set to that color), spatial frequency
spectrum (a background with a similar spectrum can be selected) and
size (a background with a similar size and/or aspect ration may be
selected). Alternatively or additionally, other display elements,
such as icons, buttons, menus and fonts may also be replaced and/or
modified in similar ways to a background.
[0030] Another aspect of some preferred embodiments of the
invention relates to generating a plurality of content-unrelated
compressed video streams from a single computer. In some preferred
embodiments of the invention, such a single computer may include a
plurality of processing units, sharing resources, such as memory
and/or a main data bus. In a preferred embodiment of the invention,
when a resource is not needed for the generation of one channel,
that resource may be used by a second channel. In a preferred
embodiment of the invention, at least some of the processing
associated with the generation of both channels is performed on a
single CPU. Preferably, a single computer generates displays for 4,
10 or even 20 channels, i.e., clients.
[0031] Another aspect of some preferred embodiments of the
invention relates to a virtual device driver for an operating
system, so that a plurality of full size windows may be displayed
simultaneously on the virtual device, by a host computer.
Preferably, each one of the full-size displays is converted into a
separate and content-unrelated video stream. In a preferred
embodiment or the invention, each window runs an instance of an
Internet browser. In a preferred embodiment of the invention, the
border and/or other portions of the browser are not shown.
Alternatively or additionally, a control area may be optionally
provided by server 16. Preferably, such a control area is overlaid
on the display.
[0032] Another aspect of some preferred embodiments of the
invention relates to broadcasting compressed video data packets
representing a plurality of display channels, where some packets
may be used for more than one channel. In one example, a packet
including data corresponding to a menu portion of a web browser is
utilized and decompressed by all the viewers which view that
particular browser. In another example, when a plurality of viewers
view a same TV or WWW channel, a temporal and/or spatial
advertisement portion of the channel may be personalized for a
particular viewer or for a group of users. The decompression unit
at each different user or group or users preferably accepts
different packets and thus may show different advertisements, on
the same channel.
[0033] Another aspect of some preferred embodiments of the
invention relates to treating WWW sites, radio stations, video on
demand, cable channels and TV channels as different instances of
multi-media presentation channels. In a preferred embodiment of the
invention, some WWW sites, such as CNN, Microsoft and the local
weather are set up as permanent channels. In some preferred
embodiments of the invention the interactivity of a channel may be
reduced in order to allow more channels in a given bandwidth.
[0034] In a preferred embodiment of the invention, such channels
may be switched between and viewed on a single display device, such
as a TV or a computer display. Alternatively or additionally, links
may be defined between portions of such channels and portions of
other such channels. Preferably, a user may follow such links to
switch between channels. Alternatively or additionally, a user may
view a plurality of such channels simultaneously and/or in an
overlay. In a preferred embodiment of the invention, linking from a
TV channel is enabled by an overlay which indicates which portions
of the channel include links and/or where such links point. In a
preferred embodiment of the invention, such links may be dynamic
and/or track portions of the image. An audio channel or a TV
channel may include an associated visual display of links and/or
may include voice annotations informing of links. In a preferred
embodiment of the invention, a link may be selected by a voice
command. In a preferred embodiment of the invention, the links are
personalized to match a particular viewer.
[0035] In a preferred embodiment of the invention, a web site may
be used to browse TV channels. When a particular link on the web
site is followed, a corresponding TV channel may be displayed. In a
preferred embodiment of the invention, a cable operator may provide
a WWW interface to browsing a TV channel catalog and especially a
video-on-demand catalog.
[0036] In a preferred embodiment of the invention, advertisements
in the multimedia channels are treated in aggregate. Thus,
advertisements may be personalized for a particular viewer,
depending on the user, for all the different types of multimedia
channel. Generation of advertisements, tracking of user viewing and
selection of advertisements shown may be effected using a single
system, albeit possibly with p different accounting for the
different types of channels.
[0037] There is therefore provided in accordance with a preferred
embodiment of the invention, a method of remote computer access,
comprising:
[0038] executing a program at a first location, to generate display
commands;
[0039] converting said display commands directly into a compressed
video data stream;
[0040] transmitting said compressed data stream to a second
location, remote from said first location;
[0041] decompressing said compressed data stream at the second
location; and
[0042] displaying the decompressed data stream as an image at the
second location.
[0043] Preferably, executing a program at a first location
comprises executing a program on a general purpose computer at said
first location. Alternatively or additionally, displaying the
decompressed data comprises displaying the decompressed data on a
TV set. Alternatively or additionally, transmitting said compressed
data comprises transmitting said compressed data over a television
distribution network. Preferably, said network comprises a cable
network.
[0044] Alternatively or additionally, said decompressing comprises
decompressing using a cable TV set-top box. Alternatively or
additionally, said program comprises a word processor.
[0045] In a preferred embodiment of the invention, said program
comprises a game program. Preferably, said program communicates
with at least a second program executed on said general purpose
computer.
[0046] In a preferred embodiment of the invention, said program
accesses data stored in association with said general purpose
computer. Preferably, said decompressed data stream comprises audio
recordings. Preferably, the method comprises tracking access to
said audio recordings for royalty payment assessment.
[0047] In a preferred embodiment of the invention, said program
comprises a browser which accesses a third location, remote from
said first and said second locations. Preferably, second remote
location is accessed via an Internet.
[0048] In a preferred embodiment of the invention, said compressed
video stream represents an entire TV display.
[0049] Preferably, the method comprises transmitting user inputs
from said remote location to said first location, responsive to
said display.
[0050] There is also provided in accordance with a preferred
embodiment of the invention, a remote computing server system,
comprising:
[0051] a server, executing a plurality of programs, each of which
generates a set of display commands; and
[0052] a video compressor which receives the plurality of sets of
display commands and generates a compressed video stream from each
one of said sets. Preferably, the server comprises a mixing box
which multiplexes said video streams unto a cable transmission
network. Alternatively or additionally, said server comprises a
mixing box which multiplexes said video streams unto a satellite
transmission network.
[0053] There is also provided in accordance with a preferred
embodiment of the invention, a method of video transmission,
comprising:
[0054] executing, at a server computer, a plurality of programs,
each of said programs generating a display responsive to an
Internet connection; and
[0055] transmitting each of said displays to a different remote
location, wherein said displays are transmitted as compressed video
streams.
[0056] Preferably, each of said programs is connected to a
different Internet address. Alternatively or additionally, each of
said programs generates a set of display commands and said
compressed video steams are directly generated from said sets of
display commands. Preferably, the method comprises generating said
compressed video streams responsive to known visual limitations at
said remote locations. Alternatively or additionally, the method
comprises generating said compressed video streams responsive to
bandwidth limitations on said transmission. Alternatively or
additionally, the method comprises degrading said display commands
responsive to bandwidth limitations on said transmission.
[0057] There is also provided in accordance with a preferred
embodiment of the invention, a multi-headed display generator,
comprising:
[0058] at least one CPU running at least one program, each of said
programs generating at least one set of display commands, wherein
said programs generate in totality at least two sets of content
independent display commands; and
[0059] at least one compressor which converts said two sets of
display commands into two simultaneous compressed video
streams,
[0060] wherein said compression of the said sets utilizes at least
one shared resource of said generator.
[0061] Preferably, said resource comprises CPU resources.
Alternatively or additionally, said resource comprises memory
resources. Alternatively or additionally, said generator trades off
the compression of one set of display commands with the compression
of a second set of display commands.
[0062] Preferably, said tradeoff comprises trading off quality
between the two command sets. Alternatively or additionally, said
tradeoff comprises trading off frame rate between the two command
sets.
[0063] In a preferred embodiment of the invention, said generator
statistically multiplexes said compressed video streams onto a
single transmission bandwidth.
[0064] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0065] receiving a plurality of display commands; and
[0066] directly converting said commands into a compressed video
stream, without first generating a display raster.
[0067] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0068] receiving a plurality of display commands; and
[0069] directly converting said commands into said compressed video
stream, wherein said converting comprises motion estimation and
wherein said motion estimation is performed directly on said
commands without first generating a display raster.
[0070] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0071] receiving a plurality of display commands; and
[0072] directly converting said commands into said compressed video
stream, wherein said converting comprises change detection and
wherein said change detection is performed directly on said
commands without first generating a display raster.
[0073] There is also provided in accordance with a preferred
embodiment of the invention, a method of motion estimation for
image stream compression, comprising:
[0074] providing a plurality of display commands;
[0075] identifying display manipulation commands among said
commands which manipulation commands manipulate image portions in
said image stream, said portions being generated by other display
commands among said plurality of display commands; and
[0076] generating at least one motion vector, responsive to said
identified display manipulation commands.
[0077] Preferably, said display manipulation commands include a
scroll command. Alternatively or additionally, said display
manipulation command is generated as a direct result of a display
of a downloaded image in a WWW browser. Alternatively or
additionally, the method comprises reducing a difficulty of said
motion vector generation by modifying said display manipulation
commands.
[0078] Preferably, scroll-type display modification commands are
limited to multiples of a compression block size dimension.
[0079] There is also provided in accordance with a preferred
embodiment of the invention, a method of change detection for image
stream compression, comprising:
[0080] providing a plurality of display commands;
[0081] identifying commands of said plurality of commands which
affect image portions in said image stream;
[0082] identifying said image portions; and
[0083] determining if a change in one of said image portions
requires image information to be included in said image stream.
[0084] Preferably, said determining comprises determining if said
change is greater than a change threshold.
[0085] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0086] providing a plurality of display commands;
[0087] directly setting values in a transform space, responsive to
said display commands; and
[0088] creating a compressed video stream utilizing said set
values.
[0089] Preferably, said transform space comprises a DCT space.
Alternatively or additionally, directly setting comprises utilizing
transform coefficients from a look-up table. Alternatively or
additionally, directly setting comprises copying transform
coefficients from a look-up table of transformed graphical
primitives. Alternatively or additionally, wherein directly setting
comprises copying transform coefficients from a cache of
transformed image portions. Alternatively or additionally, directly
setting comprises rendering said display command into said
transform space utilizing an analytical formula associating a
graphical primitive defined by said display command with said
transform space.
[0090] In a preferred embodiment of the invention, the method
comprises modifying at least one of said display commands so that a
graphical primitive defined by said at least one display command
does not straddle an image block, for which block a set of
transform coefficients are defined according to a compression
protocol utilized by said compressed image stream.
[0091] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a catalog,
comprising:
[0092] providing a plurality of display elements;
[0093] generating a compressed video representation of each one of
said elements; and storing said compressed representations in a
memory, indexed by element.
[0094] Preferably, said display elements comprise GUI (graphical
user interface) objects.
[0095] There is also provided in accordance with a preferred
embodiment of the invention, a method-of-generating a catalog,
comprising:
[0096] receiving, during interaction with an Internet, a plurality
of objects to be displayed;
[0097] generating a compressed video representation of each one of
said objects; and
[0098] storing said compressed representations in a cache of
objects, whereby when one of said objects is received again from
said Internet at a later time, a earlier stored compressed
representation is used for display generation.
[0099] Preferably, said stored objects comprise at least one JPEG
image. Alternatively or additionally, said stored objects comprise
at least one uncompressed image. Alternatively or additionally,
said stored objects comprise a WWW page.
[0100] There is also provided in accordance with a preferred
embodiment of the invention, a method of Internet browsing,
comprising:
[0101] connecting to an Internet;
[0102] receiving over said Internet at least one object to
display;
[0103] retrieving a compressed representation of said object from a
catalog; and
[0104] generating a compressed video stream utilizing said
compressed representation.
[0105] Preferably, said object comprises a WWW page.
[0106] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0107] generating a plurality of display commands which represents
a display, by a program;
[0108] modifying at least one of said display commands,
independently of said program; and
[0109] generating a compressed video stream utilizing said display
commands.
[0110] Preferably, said modifying comprises modifying said commands
to responsive to limitations of a display device on which said
compressed video stream is to be displayed. Alternatively or
additionally, modifying comprises modifying said commands to reduce
bandwidth requirements of said compressed video stream.
Alternatively or additionally, modifying comprises modifying said
commands to reduce resource requirements for compressing said
compressed video stream. Alternatively or additionally, at least
one of said display commands represents an object and said
modifying comprises changing said at least one display command such
that the object is moved relative to its original display
position.
[0111] Preferably, said compressed video stream comprises utilizes
blocks having boundaries and wherein moving comprises moving said
object to match at least one compression block boundary.
[0112] In a preferred embodiment of the invention, at least one of
said display commands represents an object and said modifying
comprises replacing said object with a different object.
[0113] Preferably, replacing said object comprises replacing said
object with a compressed representation of said different object.
Alternatively or additionally, said object comprises a text object.
Alternatively or additionally, said object comprises a background
of said display. Alternatively or additionally, the method
comprises analyzing said object to determine a closest suitable
replacement object.
[0114] In a preferred embodiment of the invention, modifying said
object comprises changing a font definition for said object.
Alternatively or additionally, modifying said object comprises
modifying at least one color of said object. Alternatively or
additionally, modifying a color comprises reducing a spatial
resolution of said colors. Preferably, modifying a color comprises
reducing a color range resolution of said colors.
[0115] Alternatively or additionally, modifying said object
comprises reducing a spatial resolution of said object.
[0116] In a preferred embodiment of the invention, at least one of
said display commands comprises a scrolling command, and wherein
said modifying comprises increasing a granularity of said
scrolling. Preferably, said increasing a granularity comprises
limiting said scrolling command to multiples of compression blocks
size of said compressed stream.
[0117] There is also provided in accordance with a preferred
embodiment of the: invention, a method of generating a compressed
video stream, comprising:.
[0118] generating a plurality of display commands which represents
a display;
[0119] generating a plurality of transform coefficients from said
display commands, wherein said transform coefficients are quantized
and wherein said quantization is modified responsive to limitations
a display device on which said compressed video stream is to be
displayed; and
[0120] creating a compressed video stream utilizing said
coefficients.
[0121] Preferably, said coefficients are quantized at a lower
resolution in a vertical direction of said display.
[0122] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0123] providing a display definition including a compressed
object; and
[0124] converting said display definition into a compressed video
stream, wherein converting includes transcribing at least a portion
of said compressed object, without decompressing said compressed
object.
[0125] Preferably, transcribing comprises reducing a quality level
of said compressed object. Alternatively or additionally, said
compressed stream and said compressed object are compressed
utilizing a same transform and transcribing comprises copying
transform coefficients from said compressed object to said
compressed video stream. Alternatively or additionally, said
compressed stream and said compressed object are compressed
utilizing a motion estimation representation and transcribing
comprises copying motion estimation vectors from said compressed
object to said compressed video stream. Alternatively or
additionally, converting said display definition comprises directly
converting said display representation into said compressed video
stream, without generating an intermediate image raster.
Alternatively or additionally, said compressed object comprises a
second compressed video stream, covering only a portion of said
display. Alternatively or additionally, said compressed object
comprises a compressed image, covering only a portion of said
display. Alternatively or additionally, said compressed object
comprises a compressed audio stream.
[0126] There is also provided in accordance with a preferred
embodiment of the invention, software program for WWW page design,
comprising:
[0127] a computer readable media having stored thereon:
[0128] a restriction module which receives restrictions defining
limitations imposed by a compression method to be used for
displaying WWW pages; and
[0129] a design module, which lays out display elements, responsive
to said received limitations.
[0130] Preferably, said restrictions include a block size
definition. Alternatively or additionally, said restrictions
include a bandwidth restriction, and wherein laying out of display
elements comprises selecting display elements to match said
bandwidth limitations. Alternatively or additionally, said media
has stored thereon an automated WWW page generator for a WWW
server. Preferably, the software comprises a communication module
for receiving said restrictions from a server associated with said
compression.
[0131] There is also provided in accordance with a preferred
embodiment of the invention, a compression-modified software for
performing at least one function and for generating at least one
display, comprising:
[0132] a computer readable media having stored thereon:
[0133] a functional module which performs said function; and
[0134] a compression-responsive module which receives an indication
of restrictions related to a compression of said display and which
controls said module to generate a display responsive to said
indication, wherein said display is modified relative to a display
generated without said restrictions.
[0135] Preferably, said indication comprises a message from a
computer on which said software is executed. Alternatively or
additionally, said indication comprises a configuration file.
Alternatively or additionally, said modified display is modified to
meet a bandwidth requirement. Preferably, said bandwidth
requirement is an instantaneous band-width requirement.
[0136] In a preferred embodiment of the invention, said modified
display is modified to reduce resources required for compression.
Alternatively or additionally, said display is modified by moving
at least one object, relative to its display location for a
non-compressed display. Alternatively or additionally, said display
is modified by utilizing a different object for a compressed
display than for a non-compressed display. Alternatively or
additionally, said function comprises a WWW browsing function.
[0137] There is also provided in accordance with a preferred
embodiment of the invention, a method of display control,
comprising:
[0138] transmitting a request, from a generator of a compressed
video stream, to a source of display commands, which requests
relates to said compression; and
[0139] modifying a generation of display commands, at said source,
responsive to said request.
[0140] Preferably, said source of display commands comprises a WWW
browser.
[0141] There is also provided in accordance with a preferred
embodiment of the invention, a method of image processing,
comprising:
[0142] providing an image to be compressed for transmission;
[0143] simultaneously compressing and processing said image;
[0144] transmitting said image to a remote location; and
[0145] decompressing said processed image at said remote
location.
[0146] Preferably, said simultaneously compressing and processing
comprises processing said image by modifying a quantization of at
least one transform coefficient of said image. Alternatively or
additionally, said modifying comprises increasing a quantization
granularity for vertical coefficients.
[0147] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0148] accumulating a plurality of display commands;
[0149] identifying at least one display command of said plurality,
whose effect is mooted by a later accumulated display command;
and
[0150] converting said commands into said compressed video stream,
ignoring the mooted display command.
[0151] Preferably, said mooted: display command is ignored if its
effect on said compressed video stream, in view of said later
command, is below a threshold value. Alternatively or additionally,
converting said commands comprises combining display commands.
Alternatively or additionally, said converting comprises directly
converting said commands into said compressed video stream without
first generating an image raster.
[0152] There is also provided in accordance with a preferred
embodiment of the invention, a method of video compression,
comprising:
[0153] generating a display, which generation is refreshed at a
generation refresh frame rate;
[0154] compressing, transmitting and decompressing said display;
and
[0155] displaying said display at a second refresh rate other than
said generation refresh rate and wherein said refresh is not
synchronized to said display refresh rate.
[0156] Preferably, said compressing is un-synchronized with said
generation refresh frame rate. Alternatively or additionally, said
transmitting is un-synchronized with said compressing.
[0157] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0158] generating a plurality of display commands;
[0159] accumulating at least one display command;
[0160] generating a compressed video stream from said accumulated
display commands, wherein accumulating comprises accumulating a
number of display commands responsive to instantaneous available
resources.
[0161] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0162] generating a plurality of display commands;
[0163] accumulating at least one display command;
[0164] generating a compressed video stream from said accumulated
display commands, wherein accumulating comprises accumulating a
number of display commands responsive to a desired output frame
rate.
[0165] In a preferred embodiment of the invention, generating a
compressed video stream is un-synchronized relative to said
generation of display commands. Preferably, said display commands
are generated in sets, each set associated with a display frame and
wherein said accumulating, in a single accumulation set, display
commands originating from different sets, wherein said single
accumulation set is utilized for generating a single frame of said
compressed video stream.
[0166] Alternatively or additionally, the method comprises
assigning a priority to a display command. Preferably, the method
comprises reordering said accumulated display commands, responsive
to said priority, wherein generating a compressed video stream
comprises generating a first frame in said compressed video stream
utilizing an originally later display command, prior to generating
a frame in said stream utilizing an originally earlier display
command.
[0167] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0168] generating a plurality of display commands;
[0169] generating a compressed image portion responsive to said
display commands; and
[0170] assembling a compressed video stream from said compressed
image portion and from at least one previously compressed image
portion, created prior to generation of said display commands.
[0171] Preferably, said previously compressed image portion
comprises an image portion created for a previous image of said
video stream.
[0172] There is also provided in accordance with a preferred
embodiment of the invention, a method of asynchronous video stream
compression, comprising:
[0173] providing a first data source and a second data source;
[0174] converting said first data source into a first portion of a
compressed video stream;
[0175] converting said second data source into a second portion of
a compressed video stream; and
[0176] mixing said first portion and said second portions to create
a single compressed video stream, wherein said first portion and
said second portion temporally overlap in said single compressed
video stream.
[0177] Preferably, said first portion and said second portion
utilize different frame rates. Alternatively or additionally, said
first portion and said second portion occupy different spatial
areas in a display defined by said single compressed video stream.
Alternatively or additionally, said first and said second data
sources comprise sets of display commands. Preferably, converting
said first data source and converting said second data source
comprises directly converting said data sources without generating
an intermediate image raster.
[0178] In a preferred embodiment of the invention, at least one of
said first data source and said second data source comprises an
image source. Alternatively or additionally, said first data source
comprises a display portion affected by a command entered by a user
who views said single compressed video source. Preferably, the
method comprises identifying portions of a data display which are
affected by said user command.
[0179] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a compressed
video stream, comprising:
[0180] executing a program, which program generates a set of
display commands, representative of a display;
[0181] identifying changes in said display which are responsive to
at least one type of user command; and
[0182] converting said display commands into a compressed video
stream,
[0183] wherein said changes are inserted into said compressed video
stream at a higher frame rate than other changes in said
display.
[0184] Preferably, said type of user command comprises a pointing
device command. Alternatively or additionally, said changes
comprises an indication of a selection of a GUI (graphical user
interface) element. Alternatively or additionally, the method
comprises analyzing said user command to determine display commands
which effect said identified changes.
[0185] There is also provided in accordance with a preferred
embodiment of the invention, a method of frame rate buffering
comprising:
[0186] providing a source of compressed video which generates a
compressed video stream having a variable frame rate;
[0187] providing a video display unit which receives said
compressed video frames, decompresses said video frames and
displays said video frames, wherein said unit is constrained to a
fixed frame rate; and
[0188] padding said generated compressed video frames with frames
which indicate that no change has occurred, to achieve said fixed
frame rate.
[0189] Preferably, the method comprises increasing said padding and
decreasing said variable rate, to compensate for bandwidth
limitation in transmission between said source and said display
unit. Alternatively or additionally, the method comprises
increasing said padding and decreasing said variable rate, to
compensate for an instantaneous resource limitation at said
source.
[0190] There is also provided in accordance with a preferred
embodiment of the invention, a method of personalizing advertising,
comprising:
[0191] providing a compressed video stream; and
[0192] replacing at least one spatial portion of said compressed
video stream with compressed data representing at least one
advertisement, wherein said replacement is responsive to
information associated with a viewer of said video stream.
[0193] Preferably, providing a compressed video stream comprises
converting a computer software generated display into said
compressed video stream. Preferably, said converting comprises
directly converting a sequence of display commands generated by
said software into said compressed video stream. Alternatively or
additionally, said advertisement replaces a display object of said
display. Alternatively or additionally, said replacing comprises
replacing without decompressing said compressed video stream.
[0194] There is also provided in accordance with a preferred
embodiment of the invention, a method of advertisement,
comprising
[0195] providing a compressed video stream, representing a
display;
[0196] determining an available portion of said display; and
[0197] inserting an advertisement into said available portion of
said display, wherein inserting comprises manipulating said
compressed video stream, without decompressing said compressed
video stream.
[0198] Preferably, determining an available portion comprises
receiving at least one indication of said available portion.
Preferably, providing a compressed video stream comprises
retrieving said stream from an archive location, wherein said
archive location includes a storage of said indications.
[0199] Alternatively or additionally, providing a compressed video
stream comprises converting a computer software generated display
into said compressed video stream. Preferably, said software
provides said indication. Alternatively or additionally, the method
comprises analyzing said display to determine said available
portion. Preferably, analyzing said display comprises analyzing
display commands generated by said software.
[0200] In a preferred embodiment of the invention, said software
comprises a WWW browser. Preferably, analyzing said display
comprises identifying display areas into which additional display
material is being downloaded.
[0201] There is also provided in accordance with a preferred
embodiment of the invention, a charge accumulation method,
comprising:
[0202] tracking a plurality of display transmissions from a server
generating compressed video streams to a display unit which
displays said streams, which transmissions utilize a variable video
stream quality;
[0203] determining, for each transmission, a quality level of the
video stream; and
[0204] generating a charge for using said transmissions, utilizing
said determined quality levels.
[0205] Preferably, said display transmissions comprise TV program
transmission. Alternatively or additionally, said display
transmission comprises a transmission of a computer generated
display. Preferably, said computer generated display comprises a
WWW browser display.
[0206] In a preferred embodiment of the invention, generating a
charge comprises generating a charge responsive to a predetermined
quality level.
[0207] There is also provided in accordance with a preferred
embodiment of the invention, a method of interactive TV,
comprising:
[0208] displaying, at on an interactive TV, a WWW page including
indications for TV channels;
[0209] detecting an interaction of a user with one of said
indications; and
[0210] displaying a TV channel on said interactive TV responsive to
said detection of interaction.
[0211] Preferably, said TV channel comprises a pay-on-demand
movie.
[0212] There is also provided in accordance with `a preferred
embodiment of the invention, a method of interactive TV,
comprising:
[0213] providing a compressed video stream representing a TV
channel;
[0214] overlaying on said compressed video stream an interaction
layer, including at least one control;
[0215] receiving from a viewer of said video stream an interaction
with said control, wherein said overlaying comprises overlaying a
compressed interaction layer on said compressed video, without
decompressing said compressed video; and
[0216] modifying said compressed video stream responsive to said
received interaction.
[0217] There is also provided in accordance with a preferred
embodiment of the invention, a method of bandwidth allocation for a
compressed video stream, comprising:
[0218] generating a plurality of display commands, by executing a
computer program;
[0219] converting said display commands into a compressed video
stream;
[0220] estimating a future content of said video stream; and
[0221] allocating bandwidth resources responsive to said
estimate.
[0222] There is also provided in accordance with a preferred
embodiment of the invention, a method of bandwidth allocation for a
compressed video stream, comprising:
[0223] generating a plurality of display commands, by executing a
computer program;
[0224] converting said display commands into a compressed video
stream;
[0225] estimating a future content of said video stream; and
[0226] allocating CPU resources for compression responsive to said
estimate.
[0227] In a preferred embodiment of the invention, said program
comprises a WWW browser. Preferably, estimating comprises
identifying a future download of complex display data.
Alternatively or additionally, estimating comprises identifying a
future download of a continuous data stream.
[0228] There is also provided in accordance with a preferred
embodiment of the invention, a method of bandwidth allocation for
transmitting video on a cable network, comprising:
[0229] providing a plurality of data sources;
[0230] differentially converting said data sources into compressed
video streams, responsive to an instantaneous resource restriction;
and
[0231] multiplexing said compressed video streams on a single
transmission line.
[0232] Preferably, said differentially converting comprises
converting each data source to a different frame rate compressed
video stream. Alternatively or additionally, said differentially
converting comprises, converting each data source to a different
frame quality level. Alternatively or additionally, said resource
restriction comprises a bandwidth restriction. Alternatively or
additionally, said resource restriction comprises a computing
resource restriction. Alternatively or additionally, said data
sources comprise display commands. Alternatively or additionally,
said differentially converting comprises differentially converting
responsive to a content of said data sources. Preferably, the
method comprises providing an indication of said content with said
data sources. Alternatively or additionally, the method comprises
providing an indication of said content by analyzing display
commands which are comprised in said data sources. Alternatively or
additionally, the method comprises providing an indication of said
content by a software which generates at least one of said data
sources.
[0233] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a plurality of
displays, comprising:
[0234] generating a first set of display commands, by a first
program;
[0235] generating at least a second set of display commands, by at
least a second program;
[0236] differentially affecting said first and said second
programs, to generate said display commands; and
[0237] converting each of said first and said second sets of
display commands into a compressed video stream,
[0238] wherein said differentially affecting comprises
differentially affecting to meet an instantaneous resource
limitation.
[0239] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a plurality of
displays, comprising:
[0240] generating a first set of display commands, by a first
program;
[0241] generating at least a second set of display commands, by at
least a second program;
[0242] differentially modifying said first and said sets of display
commands; and
[0243] converting each of said first and said second sets of
display commands into a compressed video stream,
[0244] wherein said differentially modifying comprises
differentially modifying to meet an instantaneous resource
limitation.
[0245] In a preferred embodiment of the invention, said resource
limitation comprises a transmission bandwidth limitation.
Alternatively or additionally, said resource limitation comprises a
limitation on CPU available to perform said conversion.
[0246] There is also provided in accordance with a preferred
embodiment of the invention, a method of bandwidth allocation,
comprising:
[0247] providing a distribution network having a bandwidth;
[0248] transmitting on said network a plurality of channels,
comprising Internet channels and TV channels; and
[0249] dynamically allocating bandwidth between Internet channels
and TV channels.
[0250] There is also provided in accordance with a preferred
embodiment of the invention, a method of transmitting a plurality
of similar compressed video channels, comprising:
[0251] transmitting a base compressed image stream on a first
channel;
[0252] transmitting modifications to said base image stream on at
least one second channel;
[0253] receiving, at a display location, said first and said second
channel;
[0254] modifying said first channel utilizing said second channel;
and
[0255] displaying said modified first channel at said display
location.
[0256] Preferably, one channel of said at least one second channel
is targeted for said display location. Alternatively or
additionally, transmitting comprises transmitting over a satellite
network. Alternatively or additionally, different display locations
utilize different ones of said at least one second channel to
modify said first channel. Alternatively or additionally, said
first channel carries a TV program and wherein said at least one
second channel carries advertisements. Alternatively or
additionally, said first channel carries a WWW site and wherein
said at least one second channel carries personalizations of said
site. Alternatively or additionally, said personalization comprises
a scrolling of an object in said site. Alternatively or
additionally, the method comprises assigning a third channel for
use as a base image channel for said display unit, responsive to an
interaction with said WWW site. Alternatively or additionally, the
method comprises modifying an interactivity level of said site
responsive to an availability of channels.
[0257] There is also provided in accordance with a preferred
embodiment of the invention, a method of statistical bit
multiplexing, comprising:
[0258] providing a plurality of compressed video streams to be
multiplexed;
[0259] providing, for at least one of said plurality of streams,
side information, indicative of a content of a frame of said
stream; and
[0260] differentially dropping bits from said at least one of
plurality of streams, responsive to said side information.
[0261] Preferably, said side information includes a minimal quality
level for said frame.
[0262] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a plurality of
unrelated image streams, comprising:
[0263] defining a virtual display on a computer;
[0264] executing a plurality of programs on said computer, each
program outputting to a different section of said display;
[0265] capturing, form each program, display commands for said
display; and
[0266] converting each of said sets of display commands into an
image stream having a content unrelated to image streams converted
from other of said sets of display commands.
[0267] Preferably, said image streams comprise compressed image
streams.
[0268] There is also provided in accordance with a preferred
embodiment of the invention, a method of generating a plurality of
unrelated audio streams, comprising:
[0269] providing a computer;
[0270] defining at least one virtual audio output on said
computer;
[0271] executing a plurality of programs on said computer, each
program outputting to said at least one audio output;
[0272] capturing, for each program, audio commands for said at
least one audio output;
[0273] converting each of said sets of audio commands into an audio
stream having a content unrelated to audio streams converted from
other of said sets of audio commands.
[0274] There is also provided in accordance with a preferred
embodiment of the invention, method of producing different display
representations at a plurality of remote locations, comprising:
[0275] transmitting a digitally encoded representation of a base
display to a plurality of remote locations;
[0276] transmitting a plurality of representations of modifications
of said base display;
[0277] receiving at a plurality of display locations said base
display and at least one representation of a modification; and
[0278] reconstructing at said display locations, said display
representations, from said base representation and said at least
one modification representations.
[0279] Preferably, said representations comprise HTML files.
Alternatively or additionally, said representations comprise sets
of display commands. Alternatively or additionally, said
representations comprise programs in a display generation language.
Preferably, the display generation language comprises JAVA.
BRIEF DESCRIPTION OF THE DRAWINGS
[0280] The invention will be more clearly understood by reference
to the following description of preferred embodiments thereof in
conjunction with the figures, wherein identical structures,
elements or parts which appear in more than one figure are labeled
with the same numeral in all the figures in which they appear, in
which:
[0281] FIG. 1 schematically illustrates a client/server
configuration, in accordance with a preferred embodiment of the
invention;
[0282] FIG. 2 schematically illustrates a server, in accordance
with a preferred embodiment of the invention;
[0283] FIG. 3 is a flowchart for a method of generating a
compressed video stream, in accordance with a preferred embodiment
of the invention; and
[0284] FIG. 4 is a schematic diagram of a cable operator
configuration, in accordance with a preferred embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0285] FIG. 1 schematically illustrates a client/server
configuration 10, in accordance with a preferred embodiment of the
invention. A server 16 communicates with a client 11, using a
compressed video signal. Typically, a single server 16 is connected
to and services a large number of clients 11. Client 11 comprises a
video display, preferably a television set 12 (TV). The compressed
video signal is preferably received by a set-top box 14 which
decompresses the compressed signal and sends a video signal to TV
12. In a preferred embodiment of the invention, set-top box 14 is
also used for viewing cable channels and/or pay-per-view
programs.
[0286] In a preferred embodiment of the invention, client 11
includes input devices 20, preferably a mouse and/or a key-board.
Alternatively, a remote-control with a small number of buttons is
used for input. Input devices 20 may be connected to server 16 via
a cable downlink connection, such as through set-top box 14. Such
connections are well known in the art and may be used for
transmitting small amounts of information back to a cable server.
One such connection is made by the NCI corporation (network
Computer Inc.). Alternatively or additionally, the connection may
be via a telephone connection 22. In a preferred embodiment of the
invention, user information, such as images and e-mail letters are
faxed to server 16.
[0287] In a preferred embodiment of the invention, input devices 20
are wireless, such as infrared or ultrasonic, and set-top box 14 or
telephone connection 22 include a suitable detector.
[0288] In some preferred embodiments of the invention, client 11
may comprise a computer 24 which can perform both the decompression
and the display. Alternatively or additionally, the compressed
video stream is used to carry data, preferably on a data channel of
the compression protocol, to computer 24, from server 16. Such data
communications may additionally or alternatively lead from computer
24 directly to server 16. Alternatively or additionally, input
devices of computer 24, such as a mouse, may be used as an input
device 20.
[0289] In one preferred embodiment of the invention, a direct
computer/server connection is used to upload files to server 16 for
transmission elsewhere and/or for downloading data files from the
Internet.
[0290] In a preferred embodiment of the invention, server 16 is
connected to an Internet 18 and client 11 is used to browse the
Internet. Alternatively, server 16 may run other programs, such as
a word processor, a spread-sheet or a computer game. In, a
preferred embodiment of the invention, the program executed by
server 16 is a program, which manages a subscriber's interaction
with the cable company. In another preferred embodiment of the
invention, the program is an e-mail program.
[0291] In one preferred embodiment of the invention, a program
executed on server 16 may be used to browse data stored at server
16, for example DVD multimedia in a preferred embodiment of the
invention, server 16 maintains a copy of information which is often
downloaded from the Internet, so that it can be simply and quickly
browsed. Such information preferably includes, games, images,
on-line journals and/or and data which is often downloaded and/or
downloaded by more than a certain number of users.
[0292] FIG. 2 schematically illustrates a server 16, in accordance
with a preferred embodiment of the invention. A program 30 is run
at server 16 and generates a display to be viewed. This display is
preferably drawn in a window on a virtual display 32. The window
portion of display 32 is compressed, preferably to comply with the
MPEG II standard. This compression may be performed by a standard
MPEG II compressor. However, in a preferred embodiment of the
invention, a special MPEG compression algorithm is used which take
into account the type of display being generated.
[0293] It should be appreciated that although an MPEG II
compression is assumed in many of the examples described herein,
the invention is not limited to being used with MPEG II
compression. Rather, many other compression mechanisms may be used,
including advanced versions of MPEG, Quick time, wavelet
compression, AVI and propriety compression protocols used by some
multimedia data compressors.
[0294] The compressed display is then preferably physically encoded
using a transport encoder 36 and mixed into an output video stream
using a mixing box 38. User input is preferably filtered out by
mixing box 38 and then directed to program 30, in a manner which
emulates natural keyboard and/or mouse input to the program.
Alternatively or additionally, especially when a special input
device 20 is used, for example a remote, a special device driver in
server 16 converts the user input into a format which can be
assimilated by program 30.
[0295] In a preferred embodiment of the invention, server 16 runs a
plurality of programs 30', the displays of which are all
compressed, encoded and mixed into a cable wire signal. Preferably,
the plurality of programs all run on a single CPU. Alternatively or
additionally, server 16 may comprise a multi-CPU platform.
Preferably, all the programs share a single virtual display.
Alternatively, at least some of the programs may utilize a separate
virtual display. Preferably, MPEG compression processes for a
plurality of programs are performed by the same CPU. Alternatively,
server 16 may include a plurality of DSP cards, which can be
dynamically assigned to perform the compression. Preferably, all
the compressed displays are transport encoded using a single
transport encoder, alternatively a plurality of encoders may be
used. Preferably, such a plurality of encoders are dynamically
assigned for a display frame. Preferably, the encoders are
genlocked and/or frame locked.
[0296] In a preferred embodiment of the invention, the various
programs independently utilize system resources of server 16. In
some cases, an operating system, such as windows NT or UNIX may
support multiple users on a single system. Alternatively or
additionally, server 16 may include software which captures
operating system, requests from the different programs 30 and then
handles the requests in a manner which is transparent to the
programs. One example of such a resource is cursor position.
Another example is copy and paste commands in which a separate
cut-buffer is preferably maintained for each program and/or user,
so that copy and paste commands on different programs do not
interact.
[0297] In a preferred embodiment of the invention, an overlay
generator 40 is used to add an overlay to virtual display 32. Such
an overlay may be used, for example, to add a cursor. Alternatively
or additionally, the overlay is used to add user specific
information which is not known by the program but which is tracked
by server 16, for example connection time.
[0298] In a preferred embodiment of the invention, overlay
generator 40 and/or other elements of server 16 may be used to add
an overlay to a TV program channel, especially a compressed
channel. Such an overlay may include WWW pages, program outputs,
links and/or dynamic and/or static displays.
[0299] In a preferred embodiment of the invention, each program 30
has assigned to it also a virtual audio card, for outputting sounds
generated by program 30. Alternatively or additionally, each
program 30 has assigned to it a virtual video card. Preferably, the
video output of the card are displayed in a window on the display.
Preferably, the inputs and/or outputs utilized by program 30 are
also managed as virtual devices, for example a virtual mouse and/or
keyboard. In a preferred embodiment of the invention, additional
virtual input and/or output devices may be associated with each
program. One example of such a device is a modem, for a user
downloading information to program 30. Another example is a voice
input channel, preferably with speech recognition. Preferably, the
virtual devices are assigned from a pool, on a demand basis.
Alternatively or additionally, a single virtual device is used for
a plurality of programs and the device driver is operative to
individually service a plurality of programs so that there is no
undesired interaction between the programs.
[0300] In a preferred embodiment of the invention, a portion of
virtual display 32 may be viewed on server 16, for monitoring
purposes. Alternatively or additionally, such a portion may be
viewed from a remote location, preferably, by a remote system
manager. Alternatively or additionally, a plurality of displays for
individual programs may be displayed simultaneously, preferably
with each one being reduced in size and with a plurality of program
windows being displayed on a single monitor. In a preferred
embodiment of the invention, server 16 is operative to record
audio, displays and/or inputs for a particular program or for a
plurality of programs. Such recording is preferably initiated by a
system manager or by a user of the program. Preferably, an
indication of such initiation is made directly to server 16 and
bypassing program 30.
[0301] In a preferred embodiment of the invention, server 16 is
connected to a printer and/or video or audio recording devices,
such as a DVD. Preferably, a user can print text or graphics and/or
record a multi-media segment using these devices and the hard copy
is preferably mailed and/or otherwise delivered to the user.
[0302] In some preferred embodiments of the invention, mixing box
38 is used to connect to different types of networks, in addition
to or instead of a cable network. In one preferred embodiment of
the invention, mixing box 38 is used to connect to a telephone
line. Preferably, a single data channel is transmitted over a
plurality of lines. Alternatively, compression algorithms adapted
for telephone lines may be used. Alternatively or additionally, an
ISDN line may be used.
[0303] Preferably, set-top box 14 is modified so that it can also
connect to the same type of network that mixing box 38 is connected
to. Alternatively an additional adapter box is used to adapt from
one network to the other.
[0304] In a preferred embodiment of the invention, a computer is
directly connected to the network instead of through a set-top box.
In one preferred embodiment of the invention, a LAN or a WAN is
used to connect server 16 and the computer. Preferably, the
compressed video data is transmitted as data packets over the
network.
[0305] FIG. 3 is a flowchart for a method of generating a
compressed video stream, in accordance with a preferred embodiment
of the invention. This flowchart is preferably repeated (50) for
each display element, where a display element is a graphical
primitive or object which is drawn by program 30 or by the
operating system. Alternatively, an entire display is built and
then compressed. Alternatively the display is processed on a
block-by block basis and each display element is a block or a
portion thereof. Preferably, the block size is 8.times.8, 16--16
pixels or another multiple of the MPEG block size. It should be
appreciated that different parts of the flowchart may be applied
with a different granularity. For example, some of the flowchart
may be performed on a frame-by-frame basis, while other parts may
be performed on a block-by-block, super-block-by-super-block or
element-by-element basis.
[0306] In a preferred embodiment of the invention, all the steps of
the flowchart are performed. However, in other preferred
embodiments of the invention, fewer than all the steps may be
performed, for example even only a single step may be
performed.
[0307] If the display element is an encoded object (52), for
example compressed, video or audio, the compressed data is
preferably transcribed (54) into the MPEG stream, rather than
decompressing and re-compressing it. When the object is displayed
on the virtual display using a WWW browser, a special viewer is
provided for this type of multimedia object so that the data is
transcribed to the MPEG stream instead of being decompressed,
"displayed" and recompressed. When the object is displayed using
the operating system of server 16, a similar transcription is
performed. In a preferred embodiment of the invention, the
resolution of the transcribed stream may also be controlled, for
example, by re-quantizing DCT coefficients in MPEG and JPEG data.
Preferably, the resolution is controlled to match bandwidth
restrictions and/or quality restrictions.
[0308] Different transcriptions are preferably used for different
types of compression, since the type and amount of reusable data is
dependent on the type of compression. For JPEG compressed images,
the DCT coefficients may be reused. Once the image is transmitted
once, it does not change, so only motion vectors are required to
describe it in future frames. MPEG compressed streams may be simply
copied. Some types of video compression do not use the DCT
transform but do contain motion estimation parameters which are
reusable by the MPEG compression process. The MPEG standard
supports several types of audio, which types can be simply copied
from the input to the MPEG stream. Alternatively or additionally,
to compressed streams, other types of encoded data may be
transcribed, for example, the encoded data may contain display
commands, which may be directly converted to compressed video,
without rendering the commands, as described herein.
[0309] In a preferred embodiment of the invention, the display is
adjusted for the TV display (56) and/or to make the compression
more efficient (58). These two types of adjustments may interact,
however, for simplicity of description they are described
separately. A TV display has several characteristics which not as
good as and/or different from a computer display, including,
resolution, frame rate, CRT scanning path, flicker problems, aspect
ratio, viewing distance color resolution and interlacing. The lower
resolution typically requires increasing a font size used or using
a more-readable font than required for a computer display. Flicker
problems are typically caused by thin horizontal lines, which are
preferably replaced by thick horizontal lines. Alternatively or
additionally, low pass filtering is applied to the image, at least
in the vertical dimension. In a preferred embodiment of the
invention, such a low pass filtering is applied by reducing the
quantization of the vertical frequency coefficients, after the
image is transformed, at least of the high frequencies. It should
be appreciated that filtering in a DCT space is not multiplication.
However, such filtering may be approximated by multiplication.
Preferably however, a look-up table is used to perform filtering.
Most preferably, the filtering is performed during the
quantization, preferably embodied in the quantization look-up
table.
[0310] The aspect ratio difference is preferably solved by pixel
interpolation. The increased viewing distance for TV is preferably
adjusted for by increasing the font size. The color resolution of a
TV per-se may be the same as a computer display. However, both the
MPEG II standard and most TV transmission standards utilize a lower
spatial resolution for color. Preferably, display elements which
depend on color resolution for their discernability are enlarged
and/or the colors used changed. In a preferred embodiment of the
invention, the display is modified so that it is suitable for
vision-challenged individuals. Preferably, such modification is
personalized to the visual abilities of a particular user, which
abilities may be associated with the user or which abilities may be
entered by the user.
[0311] There is preferably a two-way interaction between computer
generated displays and MPEG compression. The MPEG compression
affects how the display will look and the content of the display
affects the efficiency and speed of the MPEG compression. First,
some types of displays elements require many more bits to compress
than other types. Second, some types of display elements are
degraded to a greater amount than other elements, by a same amount
of compression. Third, some types of display elements are
easier/faster to compress than others. In a preferred embodiment of
the invention, display elements are modified so that they look
better, are easier to use and/or faster to compress than the
original display elements. Some examples include, manipulating
colors so that the color components can be compressed to a greater
degree; moving elements, such as bullets, so that they do not
straddle block boundaries; using fonts with fewer high-frequency
components; reducing flashing rates of colors and cursors and/or
synchronizing them with each other and/or other display changes;
reducing animation rates of animated objects; low-pass filtering,
to reduce display resolution; and/or reducing scrolling resolution,
for example to be limited to blocks and/or super-blocks, so that
motion estimation only involves moving of whole blocks. In a
preferred embodiment of the invention, a scrolling below a certain
resolution is not shown and/or is rounded up to a nearest number of
pixels divisible by 8.
[0312] In a preferred embodiment of the invention, color
manipulation and/or other types of image adjustment, except
possibly for aspect ratio correction, are not performed on
multimedia segments which are downloaded from the Internet.
[0313] Preferably, some or all of these adjustments are performed
by changing settings of program 30 and/or of the operating system.
However, in some cases, these adjustments may be simpler to perform
as a post-processing step during the display compression (58).
[0314] In a preferred embodiment of the invention, motion
estimation is performed utilizing a knowledge of the structure
and/or build-up of the display, instead of or in addition to
analyzing consecutive frames of the display (60). Preferably, this
knowledge is gleaned from the graphics commands generated by
program 30. Alternatively or additionally, especially in an
Internet browsing embodiment, this knowledge is gleaned from HTML,
Java or java script commands downloaded from the Internet.
Similarly, changes in a display which are described below as being
performed by modifying display commands, may also be performed by
modifying HTML files, possibly in a pre-processor to the
browser.
[0315] In a preferred embodiment of the invention, special note is
taken of scrolling commands, which define a motion vector for
portions of the display. Text based displays usually involve a
significant amount of scrolling. Even graphics based displays may
contain a significant amount of scrolling, since the display is
often only a window into a large underlying data space. Preferably,
very large motion vectors are allowed, for example as long as 200
pixel long. Typically, the vectors will comprise integer numbers of
pixels in the X and Y axis components. It should be appreciated
that there are several types of "scrolling" type commands,
including:
[0316] (a) scrolling of a portion of the display when a user enters
text in a word processor;
[0317] (b) scrolling of a scrollable display element;
[0318] (c) moving a window and/or a display element on the
display;
[0319] (d) horizontal and/or vertical motions of blocks of image
information; and/or
[0320] (e) scrolling of an entire horizontal or vertical swath of a
screen or of the entire screen.
[0321] In a particular example, when a WWW page is being
downloaded, portions of the display are moved around as new images
and their sizes are downloaded. In a preferred embodiment of the
invention, portions of the display are moved using scrolling-type
commands, so that only motion vectors need to be transmitted by the
compression mechanism. In a preferred embodiment of the invention,
some of the data may be scrolled to or from outside of the viewing
area. Preferably, scrolled out data may be retained by the MPEG
decompressor, for use when such data "moves" back into the
displayed area.
[0322] In addition, determining motion vectors by image analysis
can generally be performed more efficiently in most computer
generated displays than in acquired image streams. When a section
of a computer generated display moves, it is usually copied, so a
perfect correspondence between the source and the destination can
be expected and searched for. In a preferred embodiment of the
invention, the computer program is limited to movements of units of
8 or some other number, preferably integer, so that motion
estimation is faster and/or does not required pixel interpolation.
Alternatively or additionally, the virtual device driver translates
scrolling commands into units which are divisible by 8.
[0323] In a preferred embodiment of the invention, changes are
detected by focusing on pixels which were rendered and or on areas
on which display commands operated (62).
[0324] In a preferred embodiment of the invention, graphical
elements are drawn directly (64) into a transform space, such as a
DCT space or a wavelet transform space, instead of first being
drawn and then transformed. Some graphical elements can be reused
(their DCT coefficients reused), for example, window borders,
standard buttons, bullets, letters, icons, menus and/or some
images. Graphical elements can be reused between downloaded web
pages, between programs, between users and/or between different
frames of the same program. Preferably, a cache of DCT transformed
web pages is stored in addition to or instead of a cache of HTML
files. In addition, basic graphical elements can be drawn directly
as DCT coefficients, for example, pixels, line, combinations of
primitives and transformed primitives (zoom, rotate).
[0325] In some cases there is a simple analytic formula connecting
the original DCT coefficients and the transformed ones, for example
in rotations, zoom by an integer number and decimation by an
integer factor. When two primitives are both drawn in the same
block, the coefficients are added. In a preferred embodiment of the
invention, the coefficients are linearly added. Alternatively or
additionally, the adding takes into account the quantization and is
preferably performed using a look-up table. In a preferred
embodiment of the invention, when the primitives overlap, they are
split into non-overlapping portions and overlapping portions. The
non-overlapping portions are simply drawn. The drawing of the
overlapping portions depends on the type of interaction (such as
bitblt command) between the two primitives. In some cases; a sum or
an average of their DCT coefficients generates a good graphical
representation.
[0326] Alternatively or additionally, other processing may be
performed on DCT coefficients, prior to them being drawn into said
DCT space, for example, rotation, quantization, smoothing and/or
thresholding.
[0327] In a preferred embodiment of the invention, the DCT
coefficients for some primitives are calculated on-the-fly, using
analytical formulae. In one example, a single pixel, DCT
coefficients for a pixel at a location (x0, y0) in a compression
block yields the following DCT coefficient value for coefficients
(k, i): cos(2.pi.0*(k+0.5)/8)cos(2.pi.- y0(i+0.5)/8). A line is
preferably drawn as a series of pixels, each of which may be
"rendered" using the above formula. Preferably, a line is first
divided into line segments, each of which is included in a single
compression block.
[0328] Alternatively or additionally, the DCT coefficients for
basic objects are stored in tables, corresponding to positions of
the object within the block. Preferably, display elements are
modified so that they match a table entry and/or an analytic
transformation is used to modify them. It should be appreciated
that in some preferred embodiments of the invention, standard
display portions, such as borders and menus change rarely on the
display, so that they are only infrequently compressed and/or
retrieved from an appropriate lookup table.
[0329] In a preferred embodiment of the invention, display elements
are moved so that they do not straddle compression blocks.
Alternatively, or when the element is larger than a block, the
element may be split between blocks. Alternatively or additionally,
a look-up table stores coefficients for a 16.times.16 block.
Alternatively or additionally the 16.times.16 coefficients are
calculated from 8.times.8 coefficients, by interpolation.
[0330] It should be appreciated that methods for direct drawing of
elements into the DCT space and/or other transform spaces, for
other compression methods, are generally suitable for parallel
implementation, as the different coefficients can be set
independent of each other.
[0331] Up to this stage, the transformation, as described, is
generally loss-less, although lossy transformation (compression)
methods and/or thresholds can be applied even at these early
stages. Information compression is preferably achieved by
quantization of the DCT coefficients. It should be appreciated that
in many implementation, the transform step is integrated with the
quantization step, so there may be no separating line between
transformation and compression. In a preferred embodiment of the
invention, a compression depth which requires lossy compression is
determined (66). Preferably, the depth of compression is determined
responsive to external requirements (67), such as available
bandwidth or others, described below. Alternatively or
additionally, the amount of lossy compression desired for the
current display is outputted to an external environment, preferably
as part of a negotiation for bandwidth. The desired compression
depth may be dependent on the type of data displayed or on other
parameters, described below.
[0332] Additionally or alternatively to determining the compression
depth, the frame rate of the display is reduced to below a video
rate (68).
[0333] In a preferred embodiment of the invention, a plurality of
modifiable parameters are available for trading off image quality
and bandwidth. Each of these parameters may have a range in which
the image quality is minimally degraded and a range where the
quality is significantly degraded. In addition, different
parameters may, have different effects for different images types.
For example, the frame rate is not very important when viewing
text, but it is very important when playing a computer game. The
parameters which can be modified preferably include one or more
of:
[0334] (a) frame rate;
[0335] (b) DCT coefficient sampling resolution;
[0336] (c) a motion estimation threshold, below which no motion is
detected;
[0337] (d) a change estimation threshold;
[0338] (e) allowances for modifying the positions of objects, for
more efficient compression;
[0339] (f) allowance for modifying the appearance of objects;
[0340] (g) color modifications;
[0341] (h) reduced resolution in imported multimedia objects, such
as MPEG movies;
[0342] (i) accuracy of direct DCT drawing tables and
transformations;
[0343] (j) different parameter values per portion of the display,
per display element and/or graphical primitive; and/or
[0344] (k) a desired image quality.
[0345] In a preferred embodiment of the invention, different
parameters have different levels of importance, depending, inter
alia, on what is being viewed. Preferably, each program, TV set,
user and/or combinations thereof are associated with a particular
set of desired values for these parameters and their relative
importance and/or minimal and/or maximal values. Preferably, these
parameters are associated with a set-top box digital subscriber
number.
[0346] Additionally or alternatively, different values of
compression parameters may be defined for different parts of the
display, for example, standard icons and menu bars may be
compressed to a lower quality than unknown icons, since they are
more easily recognized.
[0347] Additionally or alternatively, the compression and/or
bandwidth requirements are dependent on a prediction of the future
frames. In one example, if a JPEG image is being downloaded and
displayed, less bandwidth will be required for a particular display
portion than if an MPEG video is being downloaded and
displayed.
[0348] In a preferred embodiment of the invention, the compression
is performed using a variable-bit rate, while requiring a constant
quality threshold. The quality threshold may be changed as a
function of available bandwidth, as described above.
[0349] In a preferred embodiment of the invention, the compressed
video signal may include two types of compressed data. For example,
an MPEG portion and an AVI portion. However, this may require
additional capabilities for the set-top box.
[0350] In a preferred embodiment of the invention, programming of
the set-top box is updated from server 16. This updating is
preferably performed while the TV is not in use. Preferably, the
selection of the compression parameters is a function of the TV
type (standard, digital or HDTV), its size and/or the capabilities
of the set-top box with regard to its speed, programmability and
memory. Preferably, more complex and/or efficient compression
schemes are used for more sophisticated set-top boxes.
[0351] Although the above embodiments have been described generally
with reference to MPEG compression, it should be appreciated that
they may be applied for many types of compression practiced today,
especially transform-quantize type compression methods. Non MPEG
compression types are also important when the display is not a
two-dimensional raster display, for example, when the display is a
three-dimensional raster display.
[0352] In a preferred embodiment of the invention, the method
explained with reference to FIG. 3 is performed responsive to
change events, which indicate to the image compressor that a change
has occurred in an image of a display channel. Step 62, "change
detection" is preferably utilized to determine if the change
warrants an update to the image, based on, for example, the
available bandwidth, available computing power and/or type of user
connection. In a preferred embodiment of the invention, only the
changed portion of the image is processed and a new output frame is
assembled from the newly compressed image portions and, possibly,
existing, unchanged compressed image portions. In a preferred
embodiment of the invention, three kinds of frames may be
generated:
[0353] (a) "I" frames, which include a complete image;
[0354] (b) "P" frames, which define changes over a previous image;
and/or
[0355] (c) "N" frames which indicate that no changes are to be
made.
[0356] As can be appreciated, it is desirable to minimize usage of
computational resources as well as bandwidth resources. On the
other hand, it is desirable to provide a fast feedback to at least
some user interactions. Alternatively or additionally, it is
desirable to maintain a fixed frame rate at the display unit.
Alternatively or additionally, the MPEG decompressor may be
modified to allow variable frame-rates.
[0357] In a preferred embodiment of the invention, the
compression-display process is asynchronous, so that each part of
the pipeline, e.g., image generation, compression, transmission and
decompression-display, may be separately optimized and/or otherwise
controlled.
[0358] In a preferred embodiment of the invention, the
decompression-display is maintained at a fixed frame rate by
buffering "I" and "P" type frames with "N" type frames, to maintain
a desired frame rate. In a preferred embodiment of the invention,
the "N" type frames are evenly distributed in the video stream. In
a preferred embodiment of the invention, the distribution of "N"
frames is used to effect a statistical multiplexing of "new" frames
between a plurality of channels.
[0359] In a preferred embodiment of the invention, the compression
is asynchronic, generating new compressed data only when a change
has occurred in the image. This allows the image generating program
to run at screen-update rates, possibly unrelated to the
compression frame rate. Alternatively or additionally, at least
some of the image generation--display process is synchronized, for
example, by buffering the communications between differently
synchronized portions of the image generation, compression and
display system. In one example, change events may be queued and
then processed (to effect image compression) at the desired frame
rate. Alternatively or additionally, the compression and/or
transmission portions may control the image generating program, for
example to slow down and/or provide only certain types of output.
In one example, the operating system may reduce the CPU slicewidth
of a program which is generating output too fast.
[0360] Alternatively or additionally, change events may be
asynchronously queued and/or delayed. In a preferred embodiment of
the invention, such delaying is performed which there are momentary
limitations on computing power and/or on transmission bandwidth. In
a preferred embodiment of the invention, two or more change events
may be combined so that only a single portion of an image is
compressed. In one example, two scroll commands can be combined
into a single "scroll" event. Alternatively or additionally, some
types of change events may be discarded, for example based on a
threshold and/or on an image quality requirement.
[0361] Alternatively or additionally, when an image portion is
compressed, generation of frames may be delayed, responsive to
limitations in computing power and/or bandwidth. In some cases,
some image portions may be delayed long enough that a newer version
of the portion overrides them. Alternatively or additionally, such
delays and queuing in compression and frame generation are
responsive to a desirable compression-output frame rate.
[0362] In a preferred embodiment of the invention, motion and/or
change information is provided as "side" information to the
compression process. Such side information may be generated by the
program, by analyzing the commands sent to the virtual display
driver and/or by analyzing the results of the display commands.
[0363] In a preferred embodiment of the invention, different
compression levels and/or other parameters are organized in sets. A
particular set is preferably selected based on the available
bandwidth, computing resources and/or other factors which are
described herein as affecting the compression.
[0364] In a preferred embodiment of the invention, even when the
frame rate is low, certain portions of the display may be updated
at a faster rate, for example, to provide feedback for a mouse
action, mouse motion and/or keyboard entry. This may be achieved by
sending MPEG frames in which the only blocks changed are those for
which feedback is required. In a preferred embodiment of the
invention, the user input channel is fast and asynchronic, so that
it is not delayed by frame-rate considerations.
[0365] In a preferred embodiment of the invention, different change
events have different priorities and may therefore "pass" queued
and/or delayed events, in the image generation--display pipeline.
For example a change event related to a response to a user input,
e.g. cursor motion, may have a higher priority that a system status
display. More than two priority levels may be defined. In a
preferred embodiment of the invention, each priority level may have
associated therewith a "frame rate" at which change events and/or
other processing associated with the event are handled.
Alternatively or additionally, each priority level may have other
information associated therewith, for example, allowed delay time
and/or error correction level.
[0366] In a preferred embodiment of the invention, blocks
associated with high priority levels of change events may be
automatically determined even without an indication from the
program. In one example, such changes are detected by capturing
"windows" commands, such as cursor movement and shading of
menus.
[0367] FIG. 4 is a schematic diagram of a cable operator
configuration 80, in accordance with a preferred embodiment of the
invention. In a typical cable distribution network, bandwidth must
be allocated between many services, including one or more of a
plurality of viewing channels 84, a plurality of pay-per-view
movies 88, data downloading from remote sources 90, telephone and
video-conferencing services 86 and audio channels 82. Additionally,
not shown are bandwidth requirements for data traveling from
subscribers to cable operator 80. In a preferred embodiment of the
invention, this last bandwidth is also shared with one or more
servers 16, which provide remote computer access to subscribers.
Preferably, a controller 92 assigns bandwidth portions to different
ones of the services. The video and/or data streams from the
services are preferably mixed using a mixing box 94 and distributed
using a cable distribution network 96. Although FIG. 4 generally
describes a centralized system, in some preferred embodiments of
the invention, the configuration is distributed. For example, a
plurality of servers may be provided with each one serving a small
locality. At need, a local server may be utilized to server a more
remote location. In a preferred embodiment of the invention, the
cable operator has a centralized connection to the Internet and
Internet data is transmitted using a cable data connection from the
Internet connection to a server 16 which requires it.
Alternatively, a plurality of such Internet connections may be
provided.
[0368] In a preferred embodiment of the invention, a certain amount
of bandwidth is assigned by the cable provider for use of server
16. Preferably, controller 92 trades-off between the various
services and/or between the bandwidth requirements of different
servers. Preferably, the available bandwidth for each client/server
channel is constantly changing to reflect the instantaneous
availability of bandwidth and/or the needs of the various services.
In a preferred embodiment of the invention, a statistical
multiplexing of bandwidth is performed between the channels so that
the average available bandwidth for each channel is as desired.
This allows a momentary higher bandwidth for a particular channel,
if required. Alternatively or additionally, this allows asynchronic
transmission of the different channels.
[0369] In a preferred embodiment of the invention, the relative
bandwidths assignments for each user of servers 16 are adjusted. In
accordance with one preferred embodiment of the invention, the
bandwidth is assigned between users so that a same compression
depth is achieved for each one. Alternatively or additionally, the
bandwidth is divided up so that a constant quality measure is
achieved for each user. The quality for each user may be defined
using quality measures well known in the art. Alternatively or
additionally, the quality measures may be dependent on the
compression parameters sets described above, which define which
compression parameters may be degraded, to what extent and/or what
consequence is allowable. Alternatively or additionally, bandwidth
is divided up so that a moving-window average of bandwidth is the
same for each user.
[0370] In a preferred embodiment of the invention, some users
receive more bandwidth than other users and/or are more likely to
retain their bandwidth in case of bandwidth shortage. Preferably,
users can order a certain minimal and/or average bandwidth ahead of
time. Alternatively, a user can require a certain minimal and/or
average frame rate and/or a maximal and/or average image
degradation.
[0371] It should be appreciated that different computer displays
require different amounts of bandwidth, for example, static text
displays require less bandwidth than graphical animation.
Preferably, an average bandwidth is achieved by statistically
assigning more bandwidth for complex displays and less bandwidth
for simple displays.
[0372] Additionally or alternatively, the average bandwidth
requirements for particular programs and/or WWW sites may be stored
so that the required bandwidth may be better estimated.
[0373] Alternatively or additionally, programs which generate
displays may be slowed down so that the bandwidth required is
lower. In one example, downloading of information is slowed so that
it is displayed slower. In another example, a computer game is
slowed down and/or its frame refresh rate lowered and/or its image
definition reduced so that its bandwidth requirements are lower.
One way of reducing image definition is by providing a virtual
display with a reduced resolution and/or drawing with a reduced
resolution.
[0374] In a preferred embodiment of the invention, TV programming,
especially video-on-demand programming, but possibly also other
types of TV channels, include hints for statistical multiplexing.
These hints may include an indication of the content of a frame or
frames of video. Alternatively or additionally, it may indicate a
required bandwidth. Alternatively or additionally, it may indicate
an allowed quality reduction. Thus, when two such channels are
statistically multiplexed, for example, as performed in an "iMedia"
system, the multiplexing can take into account the content of the
channels and not only their statistical properties. Such hints may
be transmitted on a data channel. Alternatively or additionally,
these hints may be provided with a stored TV programming sequence.
Alternatively or additionally, the hints may comprise hints for
advertisement insertion, for example, an indication of a portion of
a frame which may be replaced by an advertisement. These display
portions may be replaced with compressed video advertisements,
without decompressing the source channel, for example by replacing
compressed image blocks.
[0375] It should be appreciated that by controlling the compression
and/or the programs and/or the downloading of data, very fine
control over bandwidth, image quality and/or tradeoff between them
may be achieved, with a fast response time.
[0376] In a preferred embodiment of the invention, subscribers are
charged for utilizing servers 16 and the bandwidth used on cable
distribution network 96. Such billing may be a function of several
charge methods, including one or more of the following and/or
combinations thereof:
[0377] (a) per hour usage of server 16 and/or network 96 and/or
Internet connection;
[0378] (b) per CPU second of server 16;
[0379] (c) per second of time for MPEG compression;
[0380] (d) flat fee;
[0381] (e) per MPEG byte transmitted to user;
[0382] (f) per data byte downloaded from the Internet;
[0383] (g) per storage at server 16;
[0384] (h) different rates for different programs used, per usage
time or per usage time and/or count of these programs;
[0385] (i) per hardcopy generated, possibly including cost of
mailing and/or messenger to the user;
[0386] (j) per data transmitted from the user to server 16;
[0387] (k) advertisement level, where cable TV charges may be lower
if a higher advertisement level is allowed; and
[0388] (l) incentive payments, for example based on the actual
advertisements viewed.
[0389] In addition, the actual rate may be a function of one or
more of:
[0390] (a) the quality of data transmitted and/or the amount of
modification of the data;
[0391] (b) limitations imposed by a user on the bandwidth or the
quality;
[0392] (c) relative availability of the bandwidth; and/or
[0393] (d) variations in actual bandwidth.
[0394] In a preferred embodiment of the invention, the accounting
for cable services and server 16 services are combined. In a
preferred embodiment of the invention, the usage of specific
programs is tracked in order to pay royalties to the program
provider and/or copyright owner.
[0395] In a preferred embodiment of the invention, advertisements
are mixed into the compressed video stream.
[0396] In a preferred embodiment of the invention, advertisements
are added to the compressed video stream which is sent to the
client. The use of advertisements may offset some of the cost of
providing the service and/or may provide an additional income
source for the cable provider. In a preferred embodiment of the
invention, advertisements are added to the video stream in a manner
which will minimally affect using program 30 and/or browsing the
Internet.
[0397] In one preferred embodiment of the invention, advertisements
are displayed while waiting for an image or file to load and/or
while a program is busy calculating. Alternatively or additionally,
advertisements are displayed when server 16 is too busy to run
program 30.
[0398] Alternatively or additionally, advertisements are added to
the background of a display, for example underlying text. The
background may be automatically detected either by its color or by
the drawing command used to draw it, typically, a large single
color rectangle.
[0399] Alternatively or additionally, advertisements are placed in
unused portions of the screen, for example, large blank spaces.
Preferably, the advertisements are moved and/or resized and/or
clipped to reflect changes in the usage of the screen. In one
preferred embodiment of the invention, an advertisement is
minimized to an icon, which a user can open at will. Opening such
an icon may create an overlay an underlay and/or other changes in
the display, in addition to or instead of opening a window with the
advertisement.
[0400] Alternatively or additionally, advertisements are
non-rectangular. Preferably, an advertisement is selected to fit
the size, shape and/or aspect ratio of an available area.
Alternatively to selecting the advertisement, an existing
advertisement may be modified so that it meets time or space
constraints. Preferably, advertisements are inserted into areas of
the display into which images and/or video is being downloaded from
the Internet.
[0401] Alternatively or additionally, an advertisement may be used
to replace screen elements which are drawn by the operating system
of server 16 or by a standard program thereon. For example, an
advertisement (static or live) may be used to replace the cursor,
an icon and/or a per-program defined section of the screen.
[0402] In a preferred embodiment of the invention, a program and/or
a WWW browsing session may be modified using a suite of
advertisements. In an example of a soft-drink company, the cursor
is replaced with a bottle icon, loading images are replaced (during
loading) with well known advertisements and system messages are
replaced with messages which include a soft-drink related
content.
[0403] In a preferred embodiment of the invention advertisements
and/or programs have associated with them scripts which define
where advertisements can be inserted. The scripts are preferably
written in an interpreted language, such as Visual Basic.
[0404] In a preferred embodiment of the invention, the
advertisements are inserted in a different sensing modality from
what is used by a user. For example if the user is using a visual
display, audio advertisements may be used, and vice versa. In
particular, when a program is generating (only) a sound track, a
visual advertisement may be displayed.
[0405] In a preferred embodiment of the invention, server 16
automatically detects the activation of a screen-saver mode and
replaces the screen saver or a portion of it with an advertisement.
Alternatively or additionally, an advertisement may be displayed
and/or sounded if the program is not in use or no user input is
detected for a certain amount of time.
[0406] In a preferred embodiment of the invention, an artificial
pause in the usage of program 30 is inserted (for the advertiser)
and an advertisement is displayed on all or part of the display.
Preferably, certain times in the execution of program 30 are
defined as being less amenable to being interrupted. In one
example, advertisement breaks are inserted if a user stops typing
for a certain amount of time, after he types a period or after he
performs a save operation (in a word processor). In another
example, advertisement breaks are added to a browsing section when
a new page is entered and a considerable amount of data is to be
unloaded.
[0407] In a preferred embodiment of the invention, an advertisement
may be stopped or artificially shortened, when a user starts
entering input or when an image download is complete. Preferably,
preferred ending points and/or sections to be skipped are defined
for the advertisement, so that the break is clean.
[0408] In a preferred embodiment of the invention, the expected
duration of time during which an advertisement can be, displayed
and/or the size of area and changes in the size may be determined
responsive to the activities which are being performed by the user.
In one example, the time to download an image download can be
estimated. This estimation may be used to select an advertisement
which is just the right length or to select a plurality of
consecutive advertisements. If the download rate changes, the
advertisement may be shortened, lengthened or replaced,
accordingly.
[0409] In a preferred embodiment of the invention, the user can
indicate to server 16, preferably bypassing program 30, annotations
for particular advertisements. In particular, a user can indicate
to the server an advertisement which he wishes to view again, an
advertisement which he find offensive and or to indicate a general
level of advertisement content which is acceptable (or example for
parental control purposes). Additionally or alternatively, a user
can provide feedback to an advertisement. In one example, a user
can browse a WWW site associate with the advertisement. In another
example, a user can place a telephone call or a video conference
call, through the cable network to a location associated with the
advertisement.
[0410] Various types of advertisements may be used, including:
[0411] (a) static images;
[0412] (b) animation by a slowly changing image sequence;
[0413] (c) animation using a graphical program run at the
server;
[0414] (d) silent video;
[0415] (e) audio; and
[0416] (f) video with sounds.
[0417] In a preferred embodiment of the invention, the
advertisement includes a pre-defined frame rate, which may change
over the duration of the advertisement.
[0418] In a preferred embodiment of the invention, the
advertisements are pre-compressed. Alternatively or additionally,
the advertisements are DCT transformed and/or motion compensated,
but not quantized. Preferably, the quantization is determined in
the fly, as part of the bandwidth considerations. Alternatively or
additionally, the frame rate and/or size and/or shape are
determined on the fly. In a preferred embodiment of the invention,
the advertisement has associated with it "bandwidth suggestions",
which are certain sets of compression parameters which define a
local optimum in the tradeoff of bandwidth and viewing quality.
Such definitions may be per portion of the advertisement.
[0419] It should be appreciated that the bandwidth which is devoted
for the advertisement is not generally of interest to a user. In a
preferred embodiment of the invention, the above described
bandwidth optimizations and trade-offs are performed independently
of any advertisement content. Preferably, portions of the image in
which an advertisement will be placed are treated as portions which
do not need to be transmitted.
[0420] In a preferred embodiment of the invention, the
advertisement is purposely selected, preferably by server 16.
Alternatively or additionally to a selection responsive to
bandwidth and time considerations, such selection may be responsive
to one or more of:
[0421] (a) WWW page content;
[0422] (b) a particular program being executed by a user and/or a
particular action therein;
[0423] (c) demographics and/or other information associated with a
user;
[0424] (d) statistical definitions of exposure to the
advertisements;
[0425] (e) a desired temporal and/or modal distribution of a
particular advertisement or product;
[0426] (f) language; and/or
[0427] (g) local geographical considerations, for example, local
advertising.
[0428] In a preferred embodiment of the invention, a certain
exposure of a user to advertisements and/or advertisement display
rate may be desired. Preferably, when the rate is lower than
desired, advertisements are inserted more often and/or longer
advertisements are used.
[0429] In a preferred embodiment of the invention, a downloaded WWW
page includes an indication of what advertisements to insert and
where. The advertisements themselves are preferably stored locally
at server 16 or elsewhere at cable operator 80. In a preferred
embodiment of the invention, programs run at server 16 also have
advertisements associated therewith, for example with certain
actions and/or forms. In a preferred embodiment of the invention,
the advertisement indications refer to a product or a group of
products to be advertised. Alternatively or additionally, the
indications are associated with an advertisement distributor.
[0430] In a preferred embodiment of the invention, server 16
downloads a files which contains up-to-date associations between
advertisement indications and advertisements. In a preferred
embodiment of the invention, the actual advertisements shown, their
duration, their quality, an association with what the subscriber
was doing at the time and/or a user response to an advertisement,
are transmitted to an advertisement distributor so that royalty
payments and/or payments to the cable company, can be
determined.
[0431] In a preferred embodiment of the invention, advertisements
are added to a WWW page by the portion of the browser which is
supposed to display certain objects, such as AVI files. Preferably,
the browser portion displays advertisements from a local storage
while waiting for data to download so that the browser can display
the real data.
[0432] In a preferred embodiment of the invention, other content,
besides advertisement can be mixed with the display of program 30,
using methods as described for advertisements. In a preferred
embodiment of the invention, the content comprises TV channels,
especially news and sports channels. This type of mixing is
especially useful if the display of program 30 is relatively
static.
[0433] In a preferred embodiment of the invention, advertisements
are personalized, for content, at server 16 and/or the cable
provider. In a preferred embodiment of the invention, such
personalization may also be effected for non-Internet TV channels,
for programs run at server 16 (such as a word processor) and/or for
games. Thus, using any multi-media channel at a server 16 may
require a user to view personalized advertisements. In another
example, a software may require constant connection to the Internet
in order to operate properly and/or in order to limit pirating of
the program. Detection of the connection may be used for billing
purposes and/or for sending personalized advertisements to be
displayed by the program, even if the Internet connection does not
utilize a configuration as described above.
[0434] In a preferred embodiment of the invention, each subscriber
is assigned a private directory into which he can download
information and store personal files. Preferably, the client is
charged per space used. In a preferred embodiment of the invention,
a user can download programs from the Internet or from home, into
server 16 and run them at server 16. Preferably, such programs are
run in a protected mode of the operating system so that they do not
interfere with other programs. Alternatively or additionally, such
programs are run on a separate server 16 from Web browsers.
[0435] In a preferred embodiment of the invention, a set-top box
will only receive a channel if it matches a subscriber number of
the set-top box. Alternatively or additionally, especially for
channels viewable by multiple users, a channel may have associated
therewith a plurality of subscribers numbers and/or a pattern which
defines who may view the channel. In a preferred embodiment of the
invention, the display is encrypted, such that only designated
recipients may view it.
[0436] In a preferred embodiment of the invention, a password is
hardwired into a set-top box. Alternatively or additionally, a
password is entered by a user when logging unto server 16, for
example for entering the Internet, at which point all transmission
to the user may be encrypted responsive to the password.
Alternatively or additionally, the password may be used for
charging a user, so that a user may connect from different set-top
boxes.
[0437] Alternatively or additionally, the system assigns a password
to a user when he connects, based on the content the user is
viewing. In one example a single password may be provided to a
plurality of users viewing a same channel. Alternatively or
additionally, each user and/or channel may be assigned a different
password.
[0438] In a preferred embodiment of the invention, cable operator
80 comprises a plurality of computers, each suitable to run one or
more programs 30. These computers may be organized in different
servers 16. Alternatively or additionally, a plurality of computers
may be included in a single server. In one preferred embodiment of
the invention, different user's programs are run on different
computers, depending on the relative load on the computers and/or
the expected processing power required for compression and/or the
expected processing power required by a particular program 30. In a
preferred embodiment of the invention, a user can "rent" a
particular computer for a certain amount of time to be wholly or
partly dedicated to his needs. Alternatively or additionally,
different programs 30 are run on different computers, for example,
browsers are run on one computer and interactive games are run on a
different computer.
[0439] In one preferred embodiment of the invention, a program is
run on a first computer and the conversion of display command to
compressed video is performed on a different computer. Preferably,
this is achieved using a network windows operating system, such as
X11, whereby the display commands for X11 are sent to the different
computer to be converted there to an MPEG stream.
[0440] Alternatively or additionally, programs 30 may be moved
between computers, preferably in a manner transparent to the
end-user. In a preferred embodiment of the invention, each computer
has a backup computer running the same programs, so that if the
first computer crashes, the execution of the programs may be
passed, preferably seamlessly, to the second computer.
Alternatively or additionally, the computers share one or more
storage disks. Alternatively or additionally, the distribution of
programs 30 on the backup computers is different than on the live
computers, so that the probability of a crash repeating itself
and/or affecting the same programs 30, is reduced.
[0441] As can be appreciated, it is not generally desired that
individual programs 30 are aware of other programs 30 being
executed on the same server by a different subscriber. In addition,
it is not usually desirable that a program 30 be aware of the
transmission of the display by compressed video.
[0442] In an alternative preferred embodiment of the invention,
program 30 is aware of the display and/or input situation.
Preferably, such a program modifies its output and/or processing
responsive to what is happening on the server and/or responsive to
requests from the server. Preferably, program 30 is written for or
adapted for a remote access configuration as described herein.
[0443] In a preferred embodiment of the invention, the execution of
a program is affected by the display of the program results. In one
example, when the display bandwidth is reduced, the rate at which
displays are generated is also reduced. Alternatively, the display
is slowed down. For example, if the display is paused, the program
may also be paused. The opposite situation is also possible, if a
program requires less display bandwidth, it may be allotted a
higher share of the execution time. Alternatively to adjusting the
execution rate to meet the display bandwidth requirements, the
display bandwidth requirements may be adjusted to meet execution
rate requirements. Alternatively or additionally, a program 30 may
be slowed down if not enough CPU is available for it. Preferably,
the relative ranking between programs with regard to display
bandwidth and/or CPU availability is a property of the program
which a subscriber can adjust and/or where he is billed for
increased availability.
[0444] In a preferred embodiment of the invention, a user can
perform remote cross-platform application execution, using methods
described herein. A remote program is attached to a virtual display
and input device, the display is provided to the user as described
hereinabove and the user's input is provided to the remote location
as described hereinabove. Preferably, the display for the remote
program is shown as a window on the user's computer. Alternatively
or additionally, the location of a pointing device, such as a mouse
cursor, overlaid on the compressed video image is translated into a
location relative to the remote program's window, prior to
transmission thereto of the location.
[0445] In some preferred embodiments of the invention, two
subscribers are allowed to interact via the interactions of their
respective programs. Alternatively or additionally, a single
subscriber may execute more than one program simultaneously on
server 16, and be able to switch between them and/or pass data
between them and/or allow them to otherwise interact, for example
as provided in the Windows95 and/or Unix operating systems.
[0446] In one preferred embodiment of the invention, group games
and/or group simulations are allowed in which a plurality of
players interact. In one preferred embodiment of the invention,
group games are run on a single computer which generates a
plurality of display streams. Typically, a network connection will
need to be simulated between such game programs. Alternatively,
each program is run on a different computer at cable operator 80,
which computers are connected by a LAN. In Internet group games; an
Internet is preferably simulated between the games, instead of
actually passing all the interactions through the Internet.
[0447] In a preferred embodiment of the invention, one subscriber
can monitor the operation at one or more other subscribers,
preferably by having their compressed video stream incorporated
into his video stream. In one preferred embodiment of the
invention, such monitoring is part of a help desk operation, so
that a help desk operator can see exactly what a subscriber, with a
problem, is seeing. Preferably, the helpdesk operator has the
option of taking over the operation of a mouse and/or keyboard of
program, overriding the subscriber. Alternatively or additionally,
simultaneous input from both helpdesk operator and subscriber is
allowed.
[0448] In a preferred embodiment of the invention, interactive
tutoring may be performed. Since both the tutor's and the student's
programs are running on the same computer or a networked computer,
communication between them is simplified and response time may be
shortened. Alternatively or additionally, a display of the user may
be transmitted, in full size, in reduced size or clipped to the
tutor, so he can monitor the student more closely. Preferably, the
display is clipped relative to the mouse. Preferably, a plurality
of clipped areas are transmitted. Alternatively or additionally to
transmitting the student display, the tutor display may be
transmitted. If a camera is available at the tutor and/or the
student, a camera feed may also be transmitted between them.
[0449] In a preferred embodiment of the invention, a user can
generate a plurality of display channels. The plurality of channels
may be generated by multiple windows of a single program, by
multiple programs or by defining different parts of a single
display to be outputted in different channels. Such separate
channels may overlap in the virtual display space. Preferably, the
user switches between the viewing the multiple channels.
Alternatively or additionally, the user views two or more channels
simultaneously.
[0450] In a preferred embodiment of the invention, a user and/or
the cable operator generate a channel to be viewed specifically by
other users. Preferably, a plurality of users can view the channel
simultaneously. Preferably, at most one of the other users, if any,
may provide input to the channel. Alternatively, when more than one
additional user views the channel and/or provides input, the
program which generates the channel is duplicated for each channel.
Preferably, the program comprises an unduplicated portion and a
duplicated portion, so that a considerable amount of memory, CPU
time and/or disk storage space may be saved. In a preferred
embodiment of the invention, the program which generates the
channel is not run and/or is paused while there are no subscribers
connected to the channel Alternatively, the program is run but the
display is not compressed and/or not transmitted over distribution
network 96. Alternatively or additionally, the program is run at a
reduced rate and/or the display is compressed to a higher degree.
In a preferred embodiment of the invention, program 30 generates
its display based on other data channels in the cable network
system. For example, program 30 can generate a channel which
comprises a portion of a sports channel and a portion of a news
channel, text downloaded from a WWW site and a calculated
graph.
[0451] In a preferred embodiment of the invention, program 30
generates stereo video streams. In a preferred embodiment of the
invention, a compression method which allows the transmission of
stereo pairs is used. Alternatively, two video streams are
generated. Preferably, the two stereo streams are synchronized with
respect to their frame rate, image quality and/or relative phase.
Preferably, the set-top box is capable of decompressing two video
streams simultaneously. In a preferred embodiment of the invention,
where a TV that is capable of tuning to two or more channels at a
time is utilized, such two or more channels are provided by the
set-top box. Multiple channels may also be used to transmit news,
such as sport news on a secondary channel and/or to transmit
advertisements.
[0452] In addition, there are other circumstances in which two or
more display channels, generated by a single user or generated by
different users are synchronized, for example if two such channels
are viewed by a single user.
[0453] In a preferred embodiment of the invention, a single packet
may belong to two or more channels. In one example, a packet may
include data for a frame of a "Windows 95`, window, which data is
useful for many channels. In another example, a plurality of data
channels may utilize a same "I" frame but at least some different
"P" frames. By allowing overlap between packets, it is possible to
provide a large number of personalized WWW pages, using a limited
bandwidth. One example of a situation in which such overlap is
useful is in a satellite WWW broadcast system, in which a satellite
communication system having a limited bandwidth is used to provide
cable/internet/remote computing services to a plurality of
subscribers. Another example is a microwave, coax or optical cable
network, especially for a large area. Another example is a wireless
transmission system, such as used for TV broadcasting.
[0454] In a preferred embodiment of the invention, a plurality of
display channels are assigned for remote computer access. The
assignment may be fixed or it may be variable, for example,
depending on the availability of bandwidth and user requests for
different types of multimedia channels. In a preferred embodiment
of the invention, the assignment of WWW sites to channels is fixed.
Alternatively or additionally, at least some of the assignments may
change, for example by need (for example as is described below) or
based on popular request and/or scheduling considerations.
[0455] It should be appreciated that there are many WWW sites that
are view in substantially the same manner by a large number of
people, for example, a news site. Such a site could be assigned a
single channel. However, when a user follow a link from the site or
scrolls the display, that user cannot force all the other users to
scroll with him. In many cases however, only a small number of
people will be scrolling at any given moment. In addition, the
difference between what is being viewed by different subscribers
may be limited to personalized advertisements and/or other
personalizations of the WWW page. Thus, transmitting "P" frames
containing only the changes from a globally available "I" frame
require only a relatively small bandwidth. Once such a "P" frame is
transmitted, a user can view only "N,` frames until he makes his
next request. In a preferred embodiment of the invention, when a
user splits away from a group he is assigned a new channel number.
After the change is transmitted to the user, the channel may start
sending only "N" frames. Alternatively or additionally, the
globally available channel transmits only "N" frames, with a
periodic "I" frame. Alternatively or additionally, the user is
switched to a standard channel which contains only "N" frame. In a
preferred embodiment of the invention, depending on bandwidth
limitations, a user may be limited in functionality, for example
only to view WWW pages and/or follow links which have been selected
by other subscribers. Alternatively or additionally, the system may
delay in providing a channel with individualized "P" frames, until
such a channel becomes available. In some cases, a user is
presented with an hour-glass cursor, indicating that his request is
queued. Alternatively or additionally, a message is displayed
informing the user of the need to wait. Such a message may comprise
"P" frames, for example from a standard channel. Alternatively or
additionally, a link, a button and/or a menu item may be grayed
out. Alternatively or additionally, a limitation on scrolling
resolution may be used to reduce the number of required channels.
Alternatively or additionally, the personalization of
advertisements may be reduced.
[0456] Alternatively or additionally, to Internet channels, also TV
channels can benefit from such sub-channeling. In one example,
sub-channels may be used to provide advertising. Each locality may
require a different advertisement program. In a preferred
embodiment of the invention, the same channel includes several sets
of "P" frames, which may refer to a same spatial potion of a
display, for example to encode multiple possibilities for
advertising for a same screen location. However, each end user will
utilize only non-overlapping sets.
[0457] In a preferred embodiment of the invention, the listing of
which channels to read data packets from and which of the data
packets are relevant for a particular user, is provided in a data
channel associated with one or more display channels. In a
preferred embodiment of the invention, a plurality of WWW channels
and/or variations on a single WWW site are provided in a single
video channel, to reduce the need of physically switching between
channels when reading video information.
[0458] In an alternative preferred embodiment of the invention, "P"
and "I" frames can be computer files rather than compressed video
information. In one example, an "I" file contains instructions on
generating a basic display. A plurality of "P" files contain
instructions on modifications of the display. An end user receives,
for example on a data channel, a list of "I" and "P" to use to
reconstruct a desired display channel. In one example, the computer
files include HTML file sections. In another example, the files
comprise display lists. In another example, the files include
commands and/or definitions for a display generating language. For
example, an "I" file may include calls to subroutines, which
subroutines are defined differently in each "P" file. One example
of a suitable language is JAVA.
[0459] In a preferred embodiment of the invention, the computer at
server 16 is a powerful computer which can perform real-time
services not practical at a home computer and/or requiring special
software, for example speech recognition. In one preferred
embodiment of the invention, input devices 20 comprises a
microphone. A user provides voice commands to the microphone, which
are analyzed by a powerful and/or dedicated computer at server 16.
The results of the command are displayed on a TV set at the user,
as described above.
[0460] It should be appreciated that by keeping expensive software
at server 16, and on at a remote location which has a high speed
connection to server 16, the owner of the software can be better
protected against pirating of the software. The number of copies of
the software is substantially reduced. In addition, users who would
not buy the software can use it and pay royalties only for what
they use, so another inducement to piracy is removed.
[0461] In a preferred embodiment of the invention, the above
described configurations are used for dissemination of copyrighted
material. In one aspect of this embodiment, each
viewing/displaying/sounding of the material can be monitored and
charged centrally by the cable operator, simplifying accounting
processes. Additionally or alternatively, since the material is
compressed before it is sent to the subscriber, its quality is not
digital-perfect. Thus, pirated copies are of an inferior quality.
Additionally or alternatively, each copy so transmitted can be
marked with an individual copy number, preferably in a hidden
location in the data. Thus, if the copyrighted material is copied,
it is possible to trace the source of the copy.
[0462] It should be appreciated that some of the embodiments
described herein may also be performed using other types of
client/server communications, besides compressed video, for example
using data communications to a set-top box which renders displays
based on the data.
[0463] In a preferred embodiment of the invention, the browser
executed at server 16 interacts with the compression process. In
one example, server 16 may indicate to the browser a desired
compression and/or quality level. Such an indication may cause the
browser the perform display modifications, at the step of laying
out of display elements. Alternatively or additionally, it may
affect the type of graphical primitives generated by the browser.
Alternatively or additionally, a configuration file, preferably
read at start-up may define desired modifications in the browser
output. Alternatively or additionally, the browser generates a
special data output stream to server 16, in which the browser
indicates display commands which may be superfluous or which
require a large computational expenditure for compression and/or
which increase compression bandwidth. Alternatively or
additionally, the WWW page may include a plurality of display
options for at least some of the objects to be displayed. Thus, if
a resolution reduction is required, the reduction may be
pre-planned in the WWW page definition, rather than imposed after
the fact by the browser and/or server 16.
[0464] In a preferred embodiment of the invention, a WWW page
designing program preferably also includes an ability to take into
account limitations imposed by the compression and/or available
bandwidth. In a preferred embodiment of the invention, an automatic
WWW page generator, for example, one associated with a WWW server,
receives an indication of compression and/or bandwidth limitations
and therefore generates a WWW page which meets these
limitations.
[0465] It will be appreciated that the above described methods of
client-server communication and video compression may be varied in
many ways, including, changing the order of steps, which steps are
performed on-line or off-line, such as table preparation, and the
exact implementation used, which can include various hardware and
software combinations. The addition, a multiplicity of various
features has been described. It should be appreciated that
different features may be combined in different ways. In
particular, not all the features are necessary in every preferred
embodiment of the invention. For example, only some of the
efficiency enhancing steps may be used in a particular compression
system. Software as described herein is preferably provided on a
computer readable media, such as a diskette or an optical disk.
Alternatively or additionally, it may be stored on a computer, for
example in a main memory or on a hard disk, both of which are also
computer readable media
[0466] It will be appreciated by a person skilled in the art that
the present invention is not limited by what has thus far been
described. Rather, the scope of the present invention is limited
only by the following claims.
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