U.S. patent application number 11/791776 was filed with the patent office on 2008-04-24 for network managed channel change in digital networks.
Invention is credited to Kumar Ramaswamy.
Application Number | 20080098428 11/791776 |
Document ID | / |
Family ID | 36578221 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080098428 |
Kind Code |
A1 |
Ramaswamy; Kumar |
April 24, 2008 |
Network Managed Channel Change In Digital Networks
Abstract
There are provided a circuit and corresponding method for
enabling a channel change in a digital network. The circuit has
inputs for receiving a channel change stream and a normal stream.
The circuit further includes a multiplexer, a memory device, and a
picture element detector. The multiplexer is for transmitting the
channel change stream to a customer premises equipment (CPE) device
in response to a channel change request from the CPE device. The
memory device is for storing a flag that is set in response to the
channel change request from the CPE device. The flag is set to
request detection of a picture element in the normal stream. The
picture element detector is for detecting the picture element in
the normal stream subsequent to transmitting the channel change
stream. The multiplexer transmits the normal stream to the CPE
device in place of the channel change stream once the picture
element is detected in the normal stream.
Inventors: |
Ramaswamy; Kumar;
(Princeton, NJ) |
Correspondence
Address: |
Joseph J. Laks;Thomson Licensing LLC
2 Independence Way, Patent Operations
PO Box 5312
PRINCETON
NJ
08543
US
|
Family ID: |
36578221 |
Appl. No.: |
11/791776 |
Filed: |
July 15, 2005 |
PCT Filed: |
July 15, 2005 |
PCT NO: |
PCT/US05/24936 |
371 Date: |
May 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60633473 |
Dec 6, 2004 |
|
|
|
Current U.S.
Class: |
725/38 |
Current CPC
Class: |
H04N 21/4856 20130101;
H04N 21/64784 20130101; H04N 21/4316 20130101; H04N 21/4305
20130101; H04N 21/4884 20130101; H04N 21/6371 20130101; H04L
12/2801 20130101; H04N 21/431 20130101 |
Class at
Publication: |
725/038 |
International
Class: |
H04N 5/445 20060101
H04N005/445 |
Claims
1. A circuit for enabling a channel change in a digital network,
the circuit having inputs for receiving a channel change stream and
a normal stream, the circuit further comprising: a multiplexer for
transmitting the channel change stream to a customer premises
equipment (CPE) device in response to a channel change request from
the CPE device; a memory device for storing a flag that is set in
response to the channel change request from the CPE device, the
flag being set to request detection of a picture element in the
normal stream; and a picture element detector for detecting the
picture element in the normal stream subsequent to transmitting the
channel change stream, wherein said multiplexer transmits the
normal stream to the CPE device in place of the channel change
stream once the picture element is detected in the normal
stream.
2. The circuit according to claim 1, wherein the picture element is
a memoryless picture element.
3. The circuit according to claim 1, wherein the channel change
stream includes more picture elements than the normal stream.
4. The circuit according to claim 1, wherein the flag stored in the
memory device is reset, when the picture element is detected in the
normal stream.
5. The circuit according to claim 1, further comprising a variable
delay device for delaying the normal stream prior to a transmission
of the normal stream from the multiplexer to the CPE device.
6. The circuit according to claim 1, wherein the circuit is
implemented in a digital subscriber line access modem (DLSAM).
7. The circuit according to claim 1, wherein the digital network is
a digital subscriber line (DSL) network.
8. The circuit according to claim 1, wherein the picture element
comprises any of an I-slice, an I-picture, and an instantaneous
decoder refresh (IDR) picture.
9. In a circuit connected to a digital network and having inputs
for receiving a channel change stream and a normal stream, a method
for enabling a channel change in the digital network, the method
comprising the steps of: transmitting the channel change stream to
a customer premises equipment (CPE) device in response to a channel
change request from the CPE device; setting a flag, in response to
the channel change request from the CPE device, to request
detection of a picture element in the normal stream; detecting the
picture element in the normal stream subsequent to transmitting the
channel change stream; and transmitting the normal stream to the
CPE device in place of the channel change stream, once the picture
element is detected in the normal stream.
10. The method according to claim 9, wherein said picture element
is a memoryless picture element.
11. The method according to claim 9, wherein the channel change
stream includes more picture elements than the normal stream.
12. The method according to claim 9, further comprising the step of
resetting the flag, when the picture element is detected in the
normal stream.
13. The method according to claim 9, further comprising the step of
delaying the normal stream prior to a transmission of the normal
stream from the circuit to the CPE device.
14. The method according to claim 9, wherein the circuit is
implemented in a digital subscriber line access modem (DLSAM).
15. The method according to claim 9, wherein the digital network is
a digital subscriber line (DSL) network.
16. The method according to claim 9, wherein the picture element
comprises any of an I-slice, an I-picture, and an instantaneous
decoder refresh (IDR) picture.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/633,475, filed Dec. 6, 2004, which is
incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to digital networks
and, more particularly, to a method and apparatus for enabling a
channel change in a digital network.
BACKGROUND OF THE INVENTION
[0003] In a Digital Subscriber Line (DSL) multicast/broadcast video
system, Internet Protocol (IP) multicast can be used to transmit
compressed video to a set-top box (STB). The Internet Group
Management Protocol (IGMP) is a mechanism to select which channel
to watch, by sending a join request for the desired channel to a
Digital Subscriber Line Access Multiplexer (DSLAM). When that
channel is no longer desired, a leave request can be sent to the
DSLAM.
[0004] In a commercial video over DSL broadcast system, it is
desirable to allow end users to be able to change channels rapidly.
Popular video compression standards, such as MPEG-2 and
JVT/H.264/MPEG AVC use intra and inter coding. For proper decoding,
a decoder must decode a compressed video sequence beginning with an
intra-coded (I) picture or instantaneous decoder refresh (IDR)
picture or an I-slice, and then continuing to decode the subsequent
inter-coded (P and B) pictures. A Group of Pictures (GOP) may
include at least one I-picture and at least one P and/or B picture.
I-pictures typically require many more bits to code than a P or B
picture of equivalent video quality, often in the range of 3-10
times as many bits.
[0005] When a receiver initially begins receiving a program on a
particular channel, following a channel change or upon the initial
turning on of the receiver, the receiver must wait until an
I-picture is received to begin decoding properly, which causes a
delay.
[0006] To minimize channel change delay in digital video broadcast
systems, I-pictures are typically sent frequently, e.g., every N
pictures. For example, to enable a 1/2 second delay (of the video
compression portion of the system), it is common to use N=15 for 30
fps content. Since compressed I-pictures are much larger than
compressed P and B pictures, this considerably increases the
bitrate over what would be required if I-pictures were not inserted
so frequently.
[0007] In a first prior art system, a channel change stream was
encoded and transmitted along with the normal video bitstream. The
channel change stream included lower quality I-pictures that were
sent at a higher frequency than I-pictures in the normal bitstream.
When a user tuned to a new channel, playback could begin upon
receipt of the first I-pictures, in either the normal or channel
change stream.
[0008] In a second prior art system, for each program, a relatively
low bitrate, low resolution channel change stream is encoded, in
addition to the normal coded stream. When a channel change request
is received at the Customer Premises Equipment (CPE), join request
are made to both the channel change stream and the normal stream of
the newly selected program and both streams are sent down the DSL
link. The CPE then appropriately makes the switchover from the
channel change stream to the normal stream.
[0009] Since the solution in the second prior art system above
calls for both the normal and channel change stream to be sent over
the DSL link when a channel change request is made, it will result
in increased bandwidth until the CPE initiates a "leave" request on
the channel-change stream. For example, a user zapping through HD
channels could cause an increased bandwidth usage of a lower
resolution (possibly SD resolution) channel.
[0010] Accordingly, it would be desirable and highly advantageous
to have a method and apparatus for enabling a channel change in a
digital network that overcomes the above-described problems of the
prior art.
SUMMARY OF THE INVENTION
[0011] These and other drawbacks and disadvantages of the prior art
are addressed by the present invention, which is directed to a
method and apparatus for enabling a channel change in a digital
network.
[0012] According to an aspect of the present invention, there is
provided a circuit for enabling a channel change in a digital
network. The circuit has inputs for receiving a channel change
stream and a normal stream. The circuit further includes a
multiplexer, a memory device, and a picture element detector. The
multiplexer is for transmitting the channel change stream to a
customer premises equipment (CPE) device in response to a channel
change request from the CPE device. The memory device is for
storing a flag that is set in response to the channel change
request from the CPE device. The flag is set to request detection
of a picture element in the normal stream. The picture element
detector is for detecting the picture element in the normal stream
subsequent to transmitting the channel change stream. The
multiplexer transmits the normal stream to the CPE device in place
of the channel change stream once the picture element is detected
in the normal stream.
[0013] According to another aspect of the present invention, there
is provided, in a circuit connected to a digital network and having
inputs for receiving a channel change stream and a normal stream, a
method for enabling a channel change in the digital network. The
method includes the step of transmitting the channel change stream
to a customer premises equipment (CPE) device in response to a
channel change request from the CPE device. The method also
includes the step of setting a flag, in response to the channel
change request from the CPE device, to request detection of a
picture element in the normal stream. The also further includes the
step of detecting the picture element in the normal stream
subsequent to transmitting the channel change stream. Moreover, the
method includes the step of transmitting the normal stream to the
CPE device in place of the channel change stream, once the picture
element is detected in the normal stream.
[0014] These and other aspects, features and advantages of the
present invention will become apparent from the following detailed
description of exemplary embodiments, which is to be read in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention may be better understood in accordance
with the following exemplary figures, in which:
[0016] FIG. 1 shows a block diagram for an end-to-end architecture
in accordance with the principles of the present invention; and
[0017] FIG. 2 shows a flow diagram for a method for enabling a
channel change in a Digital Subscriber Line (DSL) system in
accordance with the principles of the present invention.
DETAILED DESCRIPTION
[0018] The present invention is directed to a method and apparatus
for enabling a channel change in a digital network.
[0019] Advantageously, the present invention improves upon the
first and second prior art systems described herein above,
overcoming the above-described deficiencies associated therewith.
For example, the present invention reduces bandwidth consumption
for a Customer Premises Equipment (CPE) initiated, low-delay
channel-change mechanism over a Digital Subscriber Loop (DSL)
system. In accordance with the principles of the present invention,
the request for channel change is made by the CPE. The digital
subscriber line access multiplexer (DSLAM) (or some other equipment
upstream), in response to this request, switches in a
lower-resolution channel-change stream and at an appropriate time
later, switches in the full-resolution stream.
[0020] It is to be appreciated that the phrases "customer service
equipment" (CPE) and "set top box" (STB) are used interchangeably
herein. The term "memoryless picture element" refers to a current
picture element that does depend on a preceding picture element or
a succeeding picture element. Moreover, it is to be further
appreciated that the terms "I-picture" and "memoryless picture
element" are used interchangeably herein to refer to any of
I-slices, instantaneous decoder refresh (IDR) pictures, or
I-pictures.
[0021] Moreover, it is to be appreciated that while the present
invention is primarily described herein with respect to a specific
example of a digital network, namely a digital subscriber line
(DSL) network, given the teachings of the present invention
provided herein, one of ordinary skill in the related art may
readily apply the present invention to any switched digital network
while maintaining the scope of the present invention.
[0022] The present description illustrates the principles of the
present invention. It will thus be appreciated that those skilled
in the art will be able to devise various arrangements that,
although not explicitly described or shown herein, embody the
principles of the invention and are included within its spirit and
scope.
[0023] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the principles of the invention and the concepts
contributed by the inventor to furthering the art, and are to be
construed as being without limitation to such specifically recited
examples and conditions.
[0024] Moreover, all statements herein reciting principles,
aspects, and embodiments of the invention, as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof. Additionally, it is intended that
such equivalents include both currently known equivalents as well
as equivalents developed in the future, i.e., any elements
developed that perform the same function, regardless of
structure.
[0025] Thus, for example, it will be appreciated by those skilled
in the art that the block diagrams presented herein represent
conceptual views of illustrative circuitry embodying the principles
of the invention. Similarly, it will be appreciated that any flow
charts, flow diagrams, state transition diagrams, pseudocode, and
the like represent various processes which may be substantially
represented in computer readable media and so executed by a
computer or processor, whether or not such computer or processor is
explicitly shown.
[0026] The functions of the various elements shown in the figures
may be provided through the use of dedicated hardware as well as
hardware capable of executing software in association with
appropriate software. When provided by a processor, the functions
may be provided by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some of
which may be shared. Moreover, explicit use of the term "processor"
or "controller" should not be construed to refer exclusively to
hardware capable of executing software, and may implicitly include,
without limitation, digital signal processor ("DSP") hardware,
read-only memory ("ROM") for storing software, random access memory
("RAM"), and non-volatile storage.
[0027] Other hardware, conventional and/or custom, may also be
included. Similarly, any switches shown in the figures are
conceptual only. Their function may be carried out through the
operation of program logic, through dedicated logic, through the
interaction of program control and dedicated logic, or even
manually, the particular technique being selectable by the
implementer as more specifically understood from the context.
[0028] In the claims hereof, any element expressed as a means for
performing a specified function is intended to encompass any way of
performing that function including, for example, a) a combination
of circuit elements that performs that function or b) software in
any form, including, therefore, firmware, microcode or the like,
combined with appropriate circuitry for executing that software to
perform the function. The invention as defined by such claims
resides in the fact that the functionalities provided by the
various recited means are combined and brought together in the
manner which the claims call for. It is thus regarded that any
means that can provide those functionalities are equivalent to
those shown herein.
[0029] Advantageously, as noted above, the present invention
provides a method and apparatus for enabling a channel change in a
digital network including, but not limited to, a digital subscribe
line (DSL) network. The present invention provides an improvement
over prior art systems such as the second prior art system
described above, by minimizing bandwidth consumption in, e.g., a
local loop of a DSL network, as compared to the prior art.
[0030] In prior art systems such the second prior art system
described above, both the normal and channel change stream are sent
over the DSL link (local loop) when a channel change request is
made, thereby resulting in a problem of increased bandwidth until
the CPE initiates a "leave" request on the channel-change stream.
Advantageously, the present invention solves this problem.
[0031] Turning to FIG. 1, an exemplary end-to-end architecture to
which the present invention may be applied is indicated generally
by the reference numeral 100. The architecture 100 includes a
content provider 110, a regional broadband network 120, a digital
subscriber line access multiplexer (DSLAM) 130, a local loop 140,
and a set top box (STB) 150. The content provider 110 includes a
video encoder 112 having a first and a second output in signal
communication with a first and second input, respectively, of a
multiplexer 114. An output of the multiplexer 114 provides an
output of the content provider 110, which is connected in signal
communication with the regional broadband network 120. The regional
broadband network 120 is further connected in signal communication
with an input of the DSLAM 130.
[0032] The DSLAM 130 includes a demultiplexer 132 having a first
output in signal communication with an input of an I-picture
detector 133 and a second output in signal communication with an
input of an I-picture detector 134. An output of the I-picture
detector 133 is connected in signal communication with a first
input of channel change selection logic 135 and with a first input
of a delay device 136. An output of the I-picture detector 134 is
connected in signal communication with a second input of the
channel change selection logic 135 and with an input of a storage
device 137. A first output of the channel change selection logic
135 is connected in signal communication with a second input of the
delay device 136. A second output of the channel change selection
logic 135 is connected in signal communication with a first input
of a selector 138. An output of the delay device is connected in
signal communication with a second input of the selector 138. An
output of the storage device 137 is connected in signal
communication with a third input of the selector 138.
[0033] A first input of the DSLAM 130 is connected in signal
communication with an input of the demultiplexer 132, a second
input of the DSLAM 130 is connected in signal communication with a
third input of the selector 138, and an output of the DSLAM 130 is
connected in signal communication with an output of the selector
138. The second input and the output of the DSLAM 130 are connected
in signal communication with the local loop 140. It is to be
appreciated that the DSLAM 130 is also interchangeably referred to
herein as a "channel change processing unit".
[0034] The STB 150 includes a user interface 152 and a video
decoder 154. An output of the STB 150 is connected in signal
communication with the local loop 140 and with the user interface
152, and an input of the STB 150 is connected in signal
communication with the local loop 140 and with the video decoder
154.
[0035] The I-picture detectors 133, 134 are for detecting
I-pictures in the normal stream. The delay device 136 is for
providing a variable delay.
[0036] The video encoder 112 creates both a normal stream and a
channel change stream of coded pictures. The normal stream and
channel change stream are multiplexed 114 together and transmitted
over a regional broadband network 120 to the DSLAM 130. For the
sake of simplicity with respect to FIG. 1, only a single program's
encoder is shown. In an actual system, multiple programs are
supported and, thus, blocks in the figure are duplicated for each
supported program. A user makes a channel change request through
the user interface 152 in the STB 150, to indicate a switch to a
new program to be viewed. This request is forwarded to the DSLAM
130.
[0037] In a preferred embodiment of the present invention, the
channel change stream is stored in storage local (e.g., local
storage device 136) to the DSLAM 130 (or remote storage which may
be quickly accessed by the DSLAM 130). During normal viewing, the
normal stream is transmitted over the local loop 140 to the video
decoder 154 at the STB 150. When a channel change request is
initiated by the user interface of the STB 150, it is sent to the
DSLAM 130 through the local loop 140. Upon receiving the channel
change request, the DSLAM 130 begins to send the stored channel
change stream of the new program to the STB 150, beginning with an
I-picture in the channel change stream, instead of the normal
stream. Then, at a later point, the DSLAM 130 switches back to
transmitting the normal stream to the STB 150.
[0038] Sending the channel change stream in addition to the normal
stream increases the bandwidth requirement over the regional
broadband network 120. This increase is bandwidth is sustained
until a "leave" request on the channel change stream is initiated
by the STB 150.
[0039] For the purposes of the present invention, it is presumed
that the DSLAM (or upstream processing element instrumenting the
channel change request, hereinafter referred to as "DSLAM" 130) is
cognizant of the paired normal stream and channel change stream
available at its input. Moreover, it is further presumed that the
DSLAM 130 is capable of detecting when an I-picture is presented on
any input stream, e.g., using I-picture detectors 133, 134. When
the STB 150 initiates a channel change request, the DSLAM first
switches the channel-change stream automatically to the STB 150 at
the next available I-picture. The DSLAM then sets a flag to inspect
the arrival of the subsequent I-picture on the normal stream. As
was described in the first and second prior art systems described
above, for bandwidth saving reasons, the channel change stream has
more frequent I-picture while the normal stream has less frequent
I-pictures. When the subsequent I-picture has arrived on the normal
stream, it is switched to serve the customer who made the original
request.
[0040] It is to be appreciated that the present invention is more
bandwidth efficient in the DSL link (local loop 140), but does
require the DSLAM 130 (or upstream channel change processing
element) to keep track of the switch between the channel change and
normal stream functions.
[0041] Turning to FIG. 2, in a Digital Subscriber Line Access
Multiplexer (DSLAM) of a DSL system, a method for enabling a
channel change is indicated generally by the reference numeral 200.
A begin block 210 passes control to a decision block 220. The
decision block 220 determines whether or not a channel change
request has been received to play a current program. If the channel
change request has not been received, then control passes back to
decision block 220. Otherwise, if the channel change request has
been received, then control passes to a function block 222. The
function block 222 sends a channel change stream coded I-picture,
and passes control to a function block 224. The function block 224
sets a flag to inspect the arrival of a subsequent I-picture on the
normal stream, and passes control to a decision block 226. The
decision block 226 determines whether or not the subsequent
I-picture has arrived on the normal stream. If the subsequent
I-picture has not yet arrived on the normal stream, then control is
returned to decision block 226. Otherwise, if the subsequent
I-picture has arrived on the normal stream, then control is passed
to a function block 240.
[0042] The function block 240 sends the normal stream (including
the subsequent I-picture) to the individual/device requesting the
channel change, and passes control to a function block 245. The
function block 245 resets the flag, and passes control to a
decision block 250. The decision block 250 determines whether or
not a channel change request has been received to exit a current
program. If the channel change request has not been received, then
control passes back to function block 240. Otherwise, if the
channel change request has been received, then control passes to an
end block 260.
[0043] These and other features and advantages of the present
invention may be readily ascertained by one of ordinary skill in
the pertinent art based on the teachings herein. It is to be
understood that the teachings of the present invention may be
implemented in various forms of hardware, software, firmware,
special purpose processors, or combinations thereof.
[0044] Most preferably, the teachings of the present invention are
implemented as a combination of hardware and software. Moreover,
the software is preferably implemented as an application program
tangibly embodied on a program storage unit. The application
program may be uploaded to, and executed by, a machine comprising
any suitable architecture. Preferably, the machine is implemented
on a computer platform having hardware such as one or more central
processing units ("CPU"), a random access memory ("RAM"), and
input/output ("I/O") interfaces. The computer platform may also
include an operating system and microinstruction code. The various
processes and functions described herein may be either part of the
microinstruction code or part of the application program, or any
combination thereof, which may be executed by a CPU. In addition,
various other peripheral units may be connected to the computer
platform such as an additional data storage unit and a printing
unit.
[0045] It is to be further understood that, because some of the
constituent system components and methods depicted in the
accompanying drawings are preferably implemented in software, the
actual connections between the system components or the process
function blocks may differ depending upon the manner in which the
present invention is programmed. Given the teachings herein, one of
ordinary skill in the pertinent art will be able to contemplate
these and similar implementations or configurations of the present
invention.
[0046] Although the illustrative embodiments have been described
herein with reference to the accompanying drawings, it is to be
understood that the present invention is not limited to those
precise embodiments, and that various changes and modifications may
be effected therein by one of ordinary skill in the pertinent art
without departing from the scope or spirit of the present
invention. All such changes and modifications are intended to be
included within the scope of the present invention as set forth in
the appended claims.
* * * * *