U.S. patent application number 15/272810 was filed with the patent office on 2017-01-12 for systems, devices, and methods for maintaining a secure audiovisual data link with an audiovisual sink during a switching event.
The applicant listed for this patent is Crestron Electronics, Inc.. Invention is credited to Justin Kennington, Christopher Merck, Gennady Pratusevich, Adolfo Velasco.
Application Number | 20170013294 15/272810 |
Document ID | / |
Family ID | 52278217 |
Filed Date | 2017-01-12 |
United States Patent
Application |
20170013294 |
Kind Code |
A1 |
Velasco; Adolfo ; et
al. |
January 12, 2017 |
SYSTEMS, DEVICES, AND METHODS FOR MAINTAINING A SECURE AUDIOVISUAL
DATA LINK WITH AN AUDIOVISUAL SINK DURING A SWITCHING EVENT
Abstract
When switching sources, resolutions or refresh rates in a video
distribution network, switching times are reduced by maintaining
video lock and security authentication between a video switcher and
a video sink. The scaler maintains video lock and security
authentication by continuing to generate video timing data during
switching events. The scaler also facilitates an aesthetically
pleasing transition by generating image content data prior to and
after the switching event.
Inventors: |
Velasco; Adolfo; (Dumont,
NJ) ; Kennington; Justin; (Magnolia, TX) ;
Merck; Christopher; (Hoboken, NJ) ; Pratusevich;
Gennady; (West Nyack, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Crestron Electronics, Inc. |
Rockleigh |
NJ |
US |
|
|
Family ID: |
52278217 |
Appl. No.: |
15/272810 |
Filed: |
September 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14500938 |
Sep 29, 2014 |
9456236 |
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15272810 |
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13764315 |
Feb 11, 2013 |
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14500938 |
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61883719 |
Sep 27, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 2012/2849 20130101;
H04L 12/2838 20130101; H04N 21/4627 20130101; H04N 21/4344
20130101; H04N 21/4402 20130101; H04N 21/2343 20130101; H04N
21/43635 20130101; H04N 21/4384 20130101; H04N 21/2541 20130101;
H04N 21/4367 20130101 |
International
Class: |
H04N 21/254 20060101
H04N021/254; H04L 12/28 20060101 H04L012/28; H04N 21/4367 20060101
H04N021/4367; H04N 21/434 20060101 H04N021/434 |
Claims
1. A method for switching audiovisual sources in a video
distribution network, the method comprising: (a) receiving first
audiovisual data at a switching device; (b) transmitting the
received first audiovisual data from the switching device to at
least one audiovisual data sink; (c) receiving second audiovisual
data during a switching event; (d) transmitting the switched second
audiovisual data to the at least one audiovisual data sink; and (e)
generating a notification signal a predetermined amount of time
prior to the step of outputting the switched second audiovisual
data.
2. The method according to claim 1, wherein the steps of receiving
first and second audiovisual data comprise: transmitting the first
and second audiovisual data from an audiovisual source; receiving
the transmitted first and second audiovisual data at an input board
in the switching device; transmitting the received first and second
audiovisual data from the input board; and receiving the
transmitted first and second audiovisual data from the input board
at a multiplexer in the switching device.
3. The method according to claim 1, wherein the switching event
comprises: a switch from receiving audiovisual data from a first
audiovisual source to receiving audiovisual data from a second
audiovisual source.
4. The method according to claim 1, wherein the switching event
comprises: a switch from receiving audiovisual data at a first
resolution to receiving audiovisual data at a second
resolution.
5. The method according to claim 1, wherein the switching event
comprises: a switch from receiving audiovisual data at a first
refresh rate to receiving audiovisual data at a second refresh
rate.
6. The method according to claim 1, wherein the steps of outputting
first and second audiovisual data comprises: outputting the first
and second audiovisual data from the multiplexer to an output
board; and outputting the first and second audiovisual data from
the output board to an audiovisual sink.
7. The method according to claim 1, further comprising: determining
that an audiovisual switching event will occur; transmitting a
switch signal to the multiplexer; and notifying the output board
that it will receive an output from the multiplexer a predetermined
amount of time prior to transmitting the switch signal to the
multiplexer for the switching event.
8. The method according to claim 7, wherein the step of notifying
comprises: receiving a control signal at a switcher device
processing unit (318) that indicates a switching event from the
first audiovisual data to the second audiovisual data; and
transmitting a prepare signal to the output board from the switcher
device processing unit prior to switching from the first
audiovisual data to the second audiovisual data.
9. The method according to claim 8, further comprising: in response
to receipt of the prepare signal, generating audiovisual data by a
scalar in the output board comprising a repeated frame of image
content data during the delay between receiving the first
audiovisual data and receiving the second audiovisual data.
10. The method according to claim 9, wherein the repeated frame of
image content data comprises: image content data from the first
audiovisual data.
11. The method according to claim 9, further comprising;
transmitting the audiovisual data to the audiovisual sink by the
output board using a security protocol link, and maintaining the
security protocol link as an authenticated interface by generating
a continuous stream of video timing data during the switching
event.
12. The method according to claim 9, wherein the prepare signal
comprises: a network address of the output board.
13. The method according to claim 12, further comprising:
determining a video distribution network topology.
14. The method according to claim 13 further comprising:
determining a network path to the output device.
15. The method according to claim 1, further comprising: scaling
audiovisual data at the output device to a native resolution of the
display.
16. The method according to claim 1, further comprising: continuing
to generate audiovisual data at the output device until an amount
of audiovisual data sufficient to achieve video lock is received
from the second audiovisual source.
Description
PRIORITY INFORMATION
[0001] The present application claims priority under 35 U.S.C.
.sctn.120 as a Continuation patent application to U.S.
Non-Provisional patent application Ser. No. 14/500,938 (client
matter no. CP00190-02), filed 29 Sep. 2014, which claims priority
to U.S. Provisional Patent Application Ser. No. 61/883,719, under
35 U.S.C. .sctn.119(e), filed 27 Sep. 2013 (client matter no.
CP00276-00), and which also claims priority under 35 U.S.C.
.sctn.120 as a Continuation-in-Part patent application to U.S.
Non-provisional patent application Ser. No. 13/764,315 (client
matter no. CP00190-01), filed 11 Feb. 2013, which claims priority
under 35 U.S.C. .sctn.119(e) as a Non-provisional patent
application to U.S. Provisional Patent Application Ser. No.
61/597,448 (CP00190-U.S.), filed 10 Feb. 2012, the entire contents
of all of which are expressly incorporated herein by reference, and
is related to co-pending, co-filed U.S. Non-provisional patent
application Ser. No. ______ (client matter no. CP00190-03),
entitled "Systems, Devices, and Methods for Generating a
Substantially Continuous Stream of Audiovisual Data During a
Switching Event," the entire contents of which are incorporated
herein by reference.
BACKGROUND
[0002] Technical Field
[0003] Aspects of the embodiments relate generally to video
distribution networks. More particularly, aspects of the
embodiments are directed to systems, methods, and modes for
distributing video protected by a digital rights management
scheme.
[0004] Background Art
[0005] Video distribution networks are increasingly common
installations in commercial and residential facilities. Components
of a video distribution network are typically located throughout
the facility and networked allowing video to be distributed from
one or more video source to one or more video sinks. For example, a
typical video distribution network in a home may comprise a
multitude of video sources, such as Blu-Ray disc players, media
servers, DVD players, digital video recorders (DVR), and cable
boxes. These video sources may be centrally located such as in an
equipment rack in a closet and distributed via a chain of switches
and repeaters to various video sinks, such as television displays,
computer monitors and projectors, throughout the home.
[0006] However, as the digital distribution of television, movies,
and music expands, content providers are growing increasingly
concerned about the simplicity with which content pirates can copy
and share copyrighted material. Various digital rights management
(DRM) schemes have been developed to ensure that television shows,
movies and music can only be viewed or heard by authorized parties
(i.e. paying customers). One DRM scheme to protect digital content
as it is transmitted over cables between devices is known as
High-Bandwidth Digital Content Protection (HDCP). HDCP is a
specified method developed by Digital Content Protection, L.L.C.
(DCP) for protecting copyrighted digital content as it travels
across connection interfaces and protocols such as DisplayPort
(DP), Digital Video Interface (DVI), High-Definition Multimedia
Interface (HDMI). The HDMI specification defines an interface for
carrying digital audiovisual content from a source such as a
Blu-Ray Disc player, to a sink or display device such as a
television (TV).
[0007] There are three facets to HDCP. First, there is the
authentication protocol, through which a source verifies that a
given sink is licensed to receive HDCP content. With the legitimacy
of the sink determined, encrypted HDCP content may be transmitted
between the two devices, based on shared secrets established during
the authentication protocol. The use of such shared secrets
prevents eavesdropping devices from utilizing the content. Finally,
in the event that legitimate devices are compromised to permit
unauthorized use of HDCP content, renewability allows a source to
identify such compromised devices and prevent the transmission of
HDCP content.
[0008] The HDCP authentication protocol is an exchange between an
HDCP compliant source and an HDCP compliant sink that affirms to
the source that the sink is authorized to receive HDCP content by
demonstrating knowledge of a set of secret device keys by
transmitting a key selection vector (KSV). Each HDCP device is
provided with a unique set of these secret device keys, referred to
as the device private keys (DPKs), from DCP. The communication
exchange also provides for both the HDCP compliant source and sink
to generate a shared secret value that cannot be determined by
eavesdropping on that exchange. By having that shared secret
information embedded into the demonstration of authorization, the
shared secret can then be used as a symmetric key to encrypt HDCP
content intended only for the authorized device. Thus, a
communication path is established between the HDCP source and HDCP
sink that only authorized devices can access.
[0009] In order for an HDCP compliant source to successfully
transmit protected content to one or more HDCP compliant sinks
through an HDCP compliant repeater, a more involved authentication
process must first occur. To affirm the downstream sinks to the
upstream sources, the HDCP repeater must pass along the KSVs of
each downstream receiver to the upstream source. The HDCP source
checks these KSVs against an HDCP Revocation List maintained by
DCP, LLC ("HDCP blacklist") in order to determine if each of the
downstream sinks are licensed to receive the protected content. If
all the downstream sinks are determined to be licensed to receive
the protected content, the upstream source transmits the protected
content to the HDCP repeater. It is the responsibility of the HDCP
repeater to then establish and periodically manage authenticated
links with each of its connected HDCP receivers.
[0010] While HDCP offers the benefit of encrypted content
transmission, the required authentication protocol increases the
switching delay in video distribution networks. Each time a new
path for video distribution is desired, the links forming those
paths must be authenticated. For example, when a user desires to
switch to a different video source, not only must the new video
source authenticate with the repeater, but the repeater must also
re-authenticate with the video sink. Increased switching times are
disrupting and bothersome to users. In complex video distribution
systems with multiple layers, this problem is even more amplified.
Additionally, because HDCP scheme operates under the surface, most
users do not realize that the increased time is the result of copy
protection schemes and often unfairly attribute them to the
individual components in the video distribution network.
[0011] An additional factor in the high switching delay in video
distribution units, is caused by the need for processing in video
distribution networks. Scalers are employed to change the
resolution or refresh rate of distributed video and are common
components in video distribution networks, either as separate
components or integrated into other components in the network. Each
time a video scaler receives audiovisual data at a new resolution,
there is a delay before the scaler outputs any new video. The video
scaler must load data and format before outputting scaled video.
This is known as achieving video lock. During a switching event,
each scaler in the distribution path must achieve video lock in
succession. In complex video distribution systems with multiple
layers, this delay is amplified.
[0012] Additionally, dependent on the characteristics of the
display, viewers may be subjected to disrupting video artifacts or
snow during switches. Manufacturers handle disrupted video in
different ways. Some displays may show snow when video is
disrupted. Other may display pixilated images or ghost images. Many
viewers find these display responses disturbing and lead some to
believe that there is a problem with their equipment when no such
problem exists. Users may experience the authentication process as
a delayed period with snow or disorienting video artifacts.
[0013] There is now a need for an improved switcher for use in a
video distribution network. Accordingly, it would be desirable to
provide methods, modes, and systems for distributing video
protected by a digital rights management scheme.
SUMMARY
[0014] An object of the embodiments is to substantially solve at
least the problems and/or disadvantages discussed above, and to
provide at least one or more of the advantages described below.
[0015] It is therefore a general aspect of the embodiments to
provide systems, methods, and modes for programming a control
network and more specifically for programming a control network
comprising one or more lighting, shade, and other types of
controllable devices that will obviate or minimize problems of the
type previously described.
[0016] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter.
[0017] Further features and advantages of the aspects of the
embodiments, as well as the structure and operation of the various
embodiments, are described in detail below with reference to the
accompanying drawings. It is noted that the aspects of the
embodiments are not limited to the specific embodiments described
herein. Such embodiments are presented herein for illustrative
purposes only. Additional embodiments will be apparent to persons
skilled in the relevant art(s) based on the teachings contained
herein.
[0018] Aspects of the embodiments seek to overcome or at least
ameliorate one or more of the several problems described above,
including but not limited to: reducing the switching delay of a
video distribution network transmitting video.
[0019] According to a first aspect of the embodiment, a device and
method are provided for reducing the actual and perceived switching
time of a video distribution network by outputting a continuous
stream of audiovisual data including a repeated frame of image
content data on a downstream connection of a switcher device.
[0020] According to a second aspect of the embodiments, a switcher
device comprises at least two input boards, a multiplexer and an
output board. Each of the at least two input boards are configured
for receiving audiovisual data from a video source. The multiplexer
is communicatively coupled between the at least two input boards
and a transmitter board and configured for dynamically routing
audiovisual data from the at least input boards to the transmitter
board. The output board is configured for transmitting audiovisual
data comprising a repeated frame of video to a video sink.
[0021] According to a third aspect of the embodiments, a switcher
device comprises at least two input boards, a multiplexer board and
an output board. Each of the at least two input boards is
configured for receiving audiovisual data from a video source. The
multiplexer board comprises a multiplexer communicatively coupled
between the at least two input boards and an output board and
configured for dynamically routing audiovisual data from the at
least two input boards to the output board and a processing unit in
communication with the multiplexer and the output board and
configured for transmitting a switch signal to the multiplexer and
a prepare signal to the transmitter board prior to a switching
event. The output board is configured for transmitting audiovisual
data to a video sink and comprises a receiver configured for
receiving audiovisual data routed from the multiplexer, a scaler
configured for converting audiovisual data received via the
multiplexer to video to a native resolution of the video sink,
generating video timing data at the native resolution of the video
sink during the switching event and generating image content data
comprising a repeated frame of video for a period of time until
achieving video lock in response to receiving the prepare signal,
and a transmitter configured for encrypting and transmitting
generated audiovisual data to the video sink.
[0022] According to a fourth aspect of the embodiments, an output
board for a switcher device is adapted to transmit audiovisual data
to a video sink. The output board comprises a receiver, a scaler
and a transmitter. The receiver is configured for receiving
audiovisual data. The scaler is adapted to convert the audiovisual
data to a native resolution of the video sink and adapted to
generate audiovisual data comprising a repeated frame during a
switching event. The transmitter is further adapted to encrypt and
transmit the output of the scaler.
[0023] According to a fifth aspect of the embodiments, a method is
provided for reducing switching delay when switching sources in a
video distribution network. The method comprises the steps of
receiving audiovisual data at a first input board from a first
video sink, routing audiovisual data from the first input board to
an output board, transmitting audiovisual data from the output
board to a video sink, receiving a user control signal to switch to
a second video source, generating video timing data at the output
board during a delay between receiving audiovisual data from the
first input board and receiving audiovisual data from the second
input board to maintain authenticity of security protocol link
between the output board and the video sink, generating image
content data at the output board during a delay between receiving
audiovisual data from the first input board and achieving video
lock with audiovisual data from the second input board, receiving
audiovisual data at a second input board from a second video sink,
routing audiovisual data from the second input board to the output
board, and transmitting audiovisual data from the output board to
the video sink.
[0024] According to a sixth aspect of the embodiments, a computer
program product is provided for reducing the switching time in a
video distribution network, the computer program product comprising
a computer readable storage medium having computer readable code
embodied therewith. The computer readable program code comprises
computer readable program code adapted to detect a user control
signal to switch from a first video source to a second video
source, transmit a prepare signal to a processing unit of an output
board in response to the detection of the user control signal,
detect the prepare signal, instruct a scaler to generate
audiovisual data comprising image content data further comprising a
repeated frame of video in response to the detection of the prepare
signal, cease routing audiovisual data from a first video source to
the output board, continue generating video timing data at the
scaler of the output board, begin routing audiovisual data from a
second video source to the input board, and cease generating image
content data upon achieving video lock.
[0025] According to a seventh aspect of the embodiments, a switcher
device is provided, comprising: at least one output board; at least
two input boards, each of the at least two input boards adapted to
receive audiovisual data from a respective audiovisual source via a
respective audiovisual link; a multiplexer communicatively coupled
between the at least two input boards and the at least one output
board, and adapted to dynamically switch audiovisual data from the
at least two input boards to the at least one output board; and a
switcher device processing unit adapted to notify the at least one
output board that it will receive an output from the multiplexer a
predetermined amount of time prior to transmitting a switch signal
to the multiplexer for a switching event.
[0026] According to the seventh aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
from a first audiovisual source to receiving audiovisual data from
a second audiovisual source.
[0027] According to the seventh aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
at a first resolution to receiving audiovisual data at a second
resolution.
[0028] According to the seventh aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
at a first refresh rate to receiving audiovisual data at a second
refresh rate.
[0029] According to the seventh aspect of the embodiments, the at
least one output board comprises: an output board processing unit,
and wherein the switcher device processing unit is further adapted
to transmit a prepare signal to the output board processing unit a
predetermined amount of time before transmitting a switch signal to
the multiplexer for the switching event.
[0030] According to the seventh aspect of the embodiments, the
prepare signal comprises: a network address of the at least output
board.
[0031] According to the seventh aspect of the embodiments, the
prepare signal is transmitted as a user datagram protocol
packet.
[0032] According to the seventh aspect of the embodiments, the at
least one output board is adapted to (i) transmit audiovisual data
to an audiovisual sink via an audiovisual link, (ii) generate
audiovisual data comprising a repeated frame of image content data,
and (iii) output a substantially continuous stream of audiovisual
data during the switching event, the audiovisual data comprising
the repeated frame of image content data, and wherein the at least
one output board further comprises a scaler adapted to generate the
repeated frame of image content data during the switching event,
and wherein the at least one output board is adapted to transmit
audiovisual data to the audiovisual sink via a security protocol
link, and is further adapted to maintain the security protocol link
as an authenticated interface by generating a continuous stream of
video timing data during the switching event.
[0033] According to the seventh aspect of the embodiments, the
scaler is further adapted to substantially continuously output the
repeated frame of image content data until receiving a sufficient
amount of audiovisual data after the switching event to achieve
video lock.
[0034] According to the seventh aspect of the embodiments, the
scaler is further adapted to determine the native resolution of the
audiovisual sink from Extended Display Identification Data (EDID)
information of the audiovisual sink.
[0035] According to the seventh aspect of the embodiments, the
security protocol link is a High-bandwidth Digital Content
Protection (HDCP) link.
[0036] According to the seventh aspect of the embodiments, the
scaler is further adapted to generate the substantially continuous
stream of video timing data at a native resolution of the
audiovisual sink.
[0037] According to an eighth aspect of the embodiments, a video
distribution network is provided comprising: at least two
audiovisual sources; at least one output board; a multiplexer
communicatively coupled to both the at least two audiovisual
sources and the at least one output board; and a switcher adapted
to dynamically route audiovisual data from the at least two
audiovisual sources to the at least one output board through the
multiplexer, and is further adapted to notify the at least one
output board that it will receive an output from the multiplexer a
predetermined amount of time prior to transmitting a switch signal
to the multiplexer for a switching event.
[0038] According to the eighth aspect of the embodiments, the
switching event can be one of a switch from receiving audiovisual
data from a first audiovisual source to receiving audiovisual data
from a second audiovisual source, a switch from receiving
audiovisual data at a first resolution to receiving audiovisual
data at a second resolution, and a switch from receiving
audiovisual data at a first refresh rate to receiving audiovisual
data at a second refresh rate.
[0039] According to the eighth aspect of the embodiments, the
switcher comprises a switcher device processing unit, and the at
least one output board comprises an output board processing unit,
and wherein the switcher device processing unit is adapted to be
communicatively coupled with the multiplexer and the output device
processing unit, and the switcher device processing unit is further
adapted to transmit a prepare signal to the at least one output
board processing unit a predetermined amount of time before
transmitting a switch signal to the multiplexer for the switching
event.
[0040] According to the eighth aspect of the embodiments, the
prepare signal comprises: a network address of the at least one
output board.
[0041] According to the eighth aspect of the embodiments, the
switcher device processing unit and the output device processing
unit are communicatively coupled via an Ethernet interface.
[0042] According to the eighth aspect of the embodiments, the
prepare signal is transmitted as a user datagram protocol
packet.
[0043] According to the eighth aspect of the embodiments, the video
distribution network further comprises: at least one audiovisual
sink, and wherein the at least one output board is adapted to--be
communicatively coupled to the at least one audiovisual sink,
transmit audiovisual data to the at least one audiovisual sink via
an audiovisual link, receive the notification from the switcher,
generate audiovisual data comprising a repeated frame of image
content data in response to the notification, and output a
substantially continuous stream of audiovisual data during the
switching event, the audiovisual data comprising the repeated frame
of image content data.
[0044] According to the eighth aspect of the embodiments, the at
least one output board comprises: a scaler adapted to generate the
repeated frame of image content data during the switching event,
and wherein the at least one output board is further adapted to
transmit audiovisual data to the at least one audiovisual sink via
a security protocol link, and is further adapted to maintain the
security protocol link as an authenticated interface by generating
a substantially continuous stream of video timing data during the
switching event.
[0045] According to the eighth aspect of the embodiments, the
switcher is further adapted to determine a network topology of the
video distribution network.
[0046] According to a ninth aspect of the embodiments, an output
board in a switcher device for transmitting audiovisual data to a
video sink is provided, the output board comprising: an output
board processing unit; and a scaler adapted to generate video
timing data at a native resolution of the video sink and a repeated
frame of image content data during a switching event, wherein the
switcher device comprises a switcher device processing unit, and a
multiplexer, and wherein (a) the switcher device processing unit is
communicatively coupled with the multiplexer and the output board
processing unit, and (b) the switcher device processing unit is
adapted to notify the output board processing unit that it the
output board will receive an output from the multiplexer a
predetermined amount of time prior to transmitting a switch signal
the multiplexer for the switching event.
[0047] According to the ninth aspect of the embodiments, the
switcher device processing unit is adapted to transmit a prepare
signal to the output board processing unit a predetermined amount
of time before transmitting a switch signal to the multiplexer for
the switching event.
[0048] According to the ninth aspect of the embodiments, the output
board is further adapted to transmit audiovisual data to the video
sink via a security protocol link and is further adapted to
maintain the security protocol link as an authenticated interface
by generating a continuous stream of video timing data during the
switching event.
[0049] According to the ninth aspect of the embodiments, the
switching event is a switch from receiving audiovisual data at a
first resolution to receiving audiovisual data at a second
resolution.
[0050] According to the ninth aspect of the embodiments, the
switching event is a switch from receiving audiovisual data from a
first source to receiving audiovisual data from a second source
[0051] According to the ninth aspect of the embodiments, the
switching event is a switch from receiving audiovisual data at a
first refresh rate to receiving audiovisual data at a second
refresh rate.
[0052] According to the ninth aspect of the embodiments, the scaler
is adapted for continuing to output the repeated frame of image
content data until receiving a sufficient amount of audiovisual
data after the switching event to achieve video lock.
[0053] According to the ninth aspect of the embodiments, the scaler
determines a native resolution of the video sink from Extended
Display Identification Data (EDID) information of the video
sink.
[0054] According to a tenth aspect of the embodiments, a method for
switching audiovisual sources in a video distribution network is
provided, the method comprising: (a) receiving first audiovisual
data at a switching device; (b) transmitting the received first
audiovisual data from the switching device to at least one
audiovisual data sink; (c) receiving second audiovisual data during
a switching event; (d) transmitting the switched second audiovisual
data to the at least one audiovisual data sink; and (e) generating
a notification signal a predetermined amount of time prior to the
step of outputting the switched second audiovisual data.
[0055] According to the tenth aspect of the embodiments, the steps
of receiving first and second audiovisual data comprise:
transmitting the first and second audiovisual data from an
audiovisual source; receiving the transmitted first and second
audiovisual data at an input board in the switching device;
transmitting the received first and second audiovisual data from
the input board; and receiving the transmitted first and second
audiovisual data from the input board at a multiplexer in the
switching device.
[0056] According to the tenth aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
from a first audiovisual source to receiving audiovisual data from
a second audiovisual source.
[0057] According to the tenth aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
at a first resolution to receiving audiovisual data at a second
resolution.
[0058] According to the tenth aspect of the embodiments, the
switching event comprises: a switch from receiving audiovisual data
at a first refresh rate to receiving audiovisual data at a second
refresh rate.
[0059] According to the tenth aspect of the embodiments, the steps
of outputting first and second audiovisual data comprises:
outputting the first and second audiovisual data from the
multiplexer to an output board; and outputting the first and second
audiovisual data from the output board to an audiovisual sink.
[0060] According to the tenth aspect of the embodiments, the method
further comprises: determining that an audiovisual switching event
will occur; transmitting a switch signal to the multiplexer; and
notifying the output board that it will receive an output from the
multiplexer a predetermined amount of time prior to transmitting
the switch signal to the multiplexer for the switching event.
[0061] According to the tenth aspect of the embodiments, the step
of notifying comprises: receiving a control signal at a switcher
device processing unit that indicates a switching event from the
first audiovisual data to the second audiovisual data; and
transmitting a prepare signal to the output board from the switcher
device processing unit prior to switching from the first
audiovisual data to the second audiovisual data.
[0062] According to the tenth aspect of the embodiments, the method
further comprises: in response to receipt of the prepare signal,
generating audiovisual data by a scalar in the output board
comprising a repeated frame of image content data during the delay
between receiving the first audiovisual data and receiving the
second audiovisual data.
[0063] According to the tenth aspect of the embodiments, the
repeated frame of image content data comprises: image content data
from the first audiovisual data.
[0064] According to the tenth aspect of the embodiments, the method
further comprises: transmitting the audiovisual data to the
audiovisual sink by the output board using a security protocol
link, and maintaining the security protocol link as an
authenticated interface by generating a continuous stream of video
timing data during the switching event.
[0065] According to the tenth aspect of the embodiments, the
prepare signal comprises: a network address of the output
board.
[0066] According to the tenth aspect of the embodiments, the method
further comprises: determining a video distribution network
topology.
[0067] According to the tenth aspect of the embodiments, the method
further comprises: determining a network path to the output
device.
[0068] According to the tenth aspect of the embodiments, the method
further comprises: scaling audiovisual data at the output device to
a native resolution of the display.
[0069] According to the tenth aspect of the embodiments, the method
further comprises: continuing to generate audiovisual data at the
output device until an amount of audiovisual data sufficient to
achieve video lock is received from the second audiovisual
source.
BRIEF DESCRIPTION OF DRAWINGS
[0070] The accompanying figures further illustrate aspects of the
embodiments.
[0071] The above and other objects and features of the embodiments
will become apparent and more readily appreciated from the
following description of the embodiments with reference to the
following figures, wherein like reference numerals refer to like
parts throughout the various figures unless otherwise
specified.
[0072] FIG. 1 is a block diagram of a high-bandwidth digital
content protection (HDCP) system.
[0073] FIG. 2 is a block diagram of an HDCP system wherein two or
more HDCP devices are interconnected through at least one
HDCP-protected Interface.
[0074] FIG. 3 is a block diagram of an inventive switcher device
according to aspects of the embodiments.
[0075] FIG. 4 is a block diagram of the switcher device shown in
FIG. 3, according to aspects of the embodiments.
[0076] FIG. 5 shows a video distribution network, according to
aspects of the embodiments.
[0077] FIG. 6 is a block diagram of the output board shown in FIG.
5, according to aspects of the embodiments.
[0078] FIG. 7 is a flowchart illustrating steps in a method for
reducing the switching time in a video distribution network,
according to aspects of the embodiments.
[0079] FIG. 8 is a block diagram of a switcher device and extended
transmission board, according to aspects of the embodiments.
[0080] FIG. 9 is a flowchart illustrating steps in a method for
reducing the switching time in a video distribution network,
according to aspects of the embodiments.
[0081] FIG. 10 is a block diagram of a video distribution system,
according to aspects of the embodiments.
[0082] FIG. 11 is a flowchart illustrating steps in a method for
reducing the switching time in a video distribution network,
according to aspects of the embodiments.
[0083] FIG. 12 is a block diagram of a scaler, according to aspects
of the embodiments.
DETAILED DESCRIPTION
[0084] The embodiments are described more fully hereinafter with
reference to the accompanying drawings, in which embodiments of the
inventive concept are shown. In the drawings, the size and relative
sizes of layers and regions may be exaggerated for clarity. Like
numbers refer to like elements throughout. The embodiments can,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
inventive concept to those skilled in the art. The scope of the
embodiments is therefore defined by the appended claims.
[0085] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the embodiments. Thus, the
appearance of the phrases "in one embodiment" on "in an embodiment"
in various places throughout the specification is not necessarily
referring to the same embodiment. Further, the particular feature,
structures, or characteristics can be combined in any suitable
manner in one or more embodiments.
LIST OF REFERENCE NUMBERS FOR THE MAJOR ELEMENTS IN THE DRAWING
[0086] The following is a list of the major elements in the
drawings in numerical order. [0087] 100 High-Bandwidth Digital
Content Protection (HDCP) System [0088] 102 Interface Cable or Link
[0089] 104 Audiovisual (AN) Source [0090] 106 A/V Sink/Display
[0091] 108 Secret Device Keys [0092] 200 High Bandwidth Digital
Content Protection System [0093] 202 HDCP Content (Audiovisual
Data) [0094] 210 Control Function [0095] 212, 215 HDCP Transmitter
[0096] 214, 216 HDCP Receiver [0097] 219 Repeater [0098] 220
Central Processing Unit (CPU) [0099] 300 Video Distribution Network
[0100] 302 Switcher Device [0101] 304 Control Signal [0102] 306
Multiplexer [0103] 308 Input Board [0104] 310 Output Board [0105]
316 User Control Signal [0106] 318 Switcher Processing Unit [0107]
320 Transceiver [0108] 322 Control System [0109] 323 User Interface
Device (Wireless/Mobile Device) [0110] 324 User Interface Device
[0111] 401 Receiver [0112] 402 Output Scaler [0113] 403 Output
Processing Unit [0114] 502 Interface Cable (Link) [0115] 508
Extended Reception Board [0116] 510 Extended Transmission Board
[0117] 601 Receiver [0118] 615 HDCP Transmitter [0119] 700 Method
for Reducing the Switching Time in a Video Distribution Network
[0120] 701-715 Steps of Method 700 [0121] 900 Method for Reducing
the Switching Time in a Video Distribution Network [0122] 901-915
Steps of Method 900 [0123] 1100 Method for Reducing the Switching
Time in a Video Distribution Network [0124] 1101-1116 Steps of
Method 1100 [0125] 1201 Input Audiovisual Data [0126] 1202 Frame
Rate Processing Block [0127] 1204 Memory [0128] 1205 Output
Audiovisual Data [0129] 1206 Input Scaling Block [0130] 1208 Output
Scaling Block [0131] 1210 Free-Running Output Timing Generator
[0132] 1211 Output Video Timing Data
LIST OF ACRONYMS IN THE SPECIFICATION
[0132] [0133] The following is a list of the acronyms used in the
specification in [0134] alphabetical order. [0135] A/V Audiovisual
[0136] API Application Programming Interface [0137] ASIC
Application Specific Integrated Circuit [0138] CAT5e Category 5
Enhanced [0139] CD Compact Disk [0140] CPU Central Processing Unit
[0141] DC Direct Current [0142] DCP Digital Content Protection, LLC
[0143] DDC Display Data Channel [0144] DDWG Digital Display Working
Group [0145] DM DigitalMedia [0146] DP DisplayPort Protocol [0147]
DPDT Double Pole Double Throw [0148] DPK Device Private Keys [0149]
DPST Double Pole Single Throw [0150] DRM Digital Rights Management
[0151] DVD Digital Video Disc [0152] DVD Digital Versatile Disk
[0153] DVI Digital Video Interface [0154] DVR Digital Video
Recorder [0155] EDID Extended Display Data Channel [0156] FPGA
Field Programmable Gate Array [0157] HDCP High-Bandwidth Definition
Content Protection [0158] HDMI High Definition Multimedia Interface
[0159] HPD Hot Plug Detection [0160] KSV Key Selection Vector
[0161] LCD Light Commanding Diode [0162] PCB Printed Circuit Board
[0163] RAM Random Access Memory [0164] ROM Read Only Memory [0165]
SDK Software Development Kit [0166] SPDT Single Pole Double Throw
[0167] SPIF Serial Peripheral Interface [0168] SPST Single Pole
Single Throw [0169] STP Shielded Twisted Pair [0170] TMDS
Transition Minimized Differential Signaling [0171] TV Television
[0172] UDP User Datagram Protocol [0173] UTP Unshielded Twisted
Pair
LIST OF DEFINITIONS
[0174] Authorized device--An HDCP device that is permitted access
to HDCP content. An HDCP transmitter may test if an attached HDCP
receiver is an authorized device by successfully completing the
first and, when applicable, second part of the authentication
protocol. If the authentication protocol successfully results in
establishing authentication, then the other device is considered by
the HDCP transmitter to be an authorized device.
[0175] Downstream--Term used as an adjective to refer to being
towards the sink/display of the HDCP content stream.
[0176] DVI--Short for Digital Video (or Visual) Interface, a
digital interface standard created by the Digital Display Working
Group (DDWG) to accommodate both analog and digital monitors.
[0177] HDCP--short for High-Bandwidth Digital Content Protection, a
specified method developed by Digital Content Protection, L.L.C.
(DCP) for protecting copyrighted digital content as it travels
across connection interfaces and protocols such as DisplayPort
(DP), DVI, and HDMI, among others.
[0178] HDCP content--consists of audiovisual content that is
protected by the HDCP system. HDCP content includes the audiovisual
content in encrypted form as it is transferred from an HDCP
transmitter to an HDCP receiver over an HDCP-protected
Interface.
[0179] HDCP device--Any device that contains one or more
HDCP-protected interface ports and is designed in adherence to
HDCP.
[0180] HDCP Encryption--The encryption technology of HDCP when
applied to the protection of HDCP content in an HDCP system.
[0181] HDCP-protected Interface--An interface for which HDCP
applies.
[0182] HDCP-protected Interface Port--A connection point on an HDCP
Device that supports an HDCP-protected Interface.
[0183] HDCP receiver--An HDCP device that can receive and decrypt
HDCP content through one or more of its HDCP-protected interface
ports.
[0184] HDCP repeater--An HDCP device that can receive and decrypt
HDCP content through one or more of its HDCP-protected interface
ports, and can also re-encrypt and emit the HDCP content through
one or more of its HDCP-protected interface ports. An HDCP repeater
may also be referred to as either an HDCP receiver or an HDCP
transmitter when referring to either the upstream side or the
downstream side, respectively.
[0185] HDCP transmitter--An HDCP device that can encrypt and emit
HDCP content through one or more of its HDCP-protected interface
ports.
[0186] HDMI--Short for High-Definition Multimedia Interface, an
industry-supported, uncompressed, all-digital audio/video
interface.
[0187] Upstream--Term used as an adjective to refer to being
towards the source of the HDCP content stream. The antonym of
"downstream," defined above.
[0188] FIGS. 1 and 2 illustrate examples of HDCP systems 100, 200.
Referring to FIG. 1, the HDCP system 100 encrypts the digital
content transmission between a video source 104 (set-top box,
computer, DVD, etc.) and a sink or display 106 (liquid crystal
display (LCD), television, etc.) via an interface 102 such as DVI,
HDMI, and DP interfaces, among others.
[0189] FIG. 2 illustrates an HDCP system 200 wherein two or more
HDCP devices 104, 106 are interconnected through an HDCP repeater
and two HDCP-protected Interfaces 102a, 102b (collectively 102).
Each point-to-point HDCP link involves one HDCP transmitter 212,
and one HDCP receiver 214. As such, the HDCP repeater 219 must
decrypt the HDCP content at the HDCP receiver 216 on each of its
inputs. The repeater 219 must then re-encrypt the data with an HDCP
transmitter 215 on each of its outputs. According to an aspect of
the embodiments, repeater 219 must inform the upstream device of
its downstream connection, and repeater 219 has the responsibility
to maintain those connections. According to further aspects of the
embodiments, repeater 219 can inform the upstream device of its
downstream connector, and repeater 219 can maintain those
connections. The audiovisual content protected by HDCP, HDCP
content 202, flows from an upstream content control function 210
into the HDCP system 200 at the most upstream transmitter 212. From
there, the HDCP content 202, encrypted by the HDCP system 200,
flows through a tree-shaped topology of HDCP receivers 214 over
HDCP-protected Interfaces 102. Before sending data, the each
transmitter 212, 215 checks that the HDCP receivers 214, 216 are
authorized to receive the HDCP content 202. If so, the transmitter
212 encrypts the HDCP content 202 to prevent eavesdropping as it
flows to the receiver 216. A central processing unit 220 includes
firmware to process the data 202 and other information and
control.
[0190] Device manufacturers typically buy HDCP chips from a
DCP-licensed silicon vendor. These chips usually also provides
transition minimized differential signaling (TMDS) encoders or
decoders and other HDMI-specific features. Every transmitter 212
will have at least one HDCP transmitter chip and every receiver 216
will have at least one HDCP receiver chip. The HDCP transmitters
212, and receivers 216, frequently require a microprocessor to
implement the authentication state machines. Transmitters 212, 215
are HDMI transmitters.
[0191] Authentication and Encryption Protocols
[0192] HDCP authentication consists of three parts:
[0193] Part One: The source 104 authenticates with the sink/display
106 connected to its output. If successful, encryption is enabled
and audiovisual (NV) content transmission begins.
[0194] Part Two: This part is used if the downstream device is a
repeater 219. The repeater 219 authenticates with the devices
connected to its output(s) and passes the HDCP tree topology
information up to the source 104. The source 104 is the root and
sinks/display 106 are the leaves, while repeaters 219 make up the
branches of the tree.
[0195] Part Three: The source 104 performs periodic checks with the
sink/display 106 to ensure that encryption is in sync. As mentioned
above, it is the repeater's responsibility to maintain its
downstream connections. If any part of authentication fails or any
revoked devices are found in the HDCP tree, the transmitter 212
must stop sending protected content and authentication starts over
at Part One.
[0196] Authentication Part One
[0197] Part One of authentication is a key exchange protocol. The
transmitter 212 and receiver 216 calculate a common secret session
key 108 to be used for encryption. If they cannot come up with the
same key value, authentication fails and the receiver 216 will not
be able to decrypt the content 202. The session key is derived from
each device's private key according to the following protocol:
[0198] First, the transmitter 212 generates a random number
"A.sub.n" and sends it to the receiver 216. This value will be used
later in the protocol. The devices 104, 106 then exchange KSVs. The
receiver 216 also sends its REPEATER bit, a flag that indicates
whether or not it is part of a repeater. Now each device 104, 106
has the other device's KSV. Each device 104, 106 uses the other
device's KSV to select twenty of its own keys. The forty bits in
the KSV correspond to the indexes of each of the forty private
keys. For every set bit in the received KSV, the local private key
at that index is selected. All KSVs have twenty set bits, so twenty
keys are selected. The devices 104, 106 then each add up their
selected keys to come up with the sums Km and Km', for the
transmitter and receiver, respectively 212, 216. For authentication
to succeed, Km and Km' must match. Each device 104, 106 tells the
other which of its own unique, secret keys to select, and they both
come up with the same sum. That may seem counter-intuitive, but it
is the aforementioned mathematical relationship between the keys
and the KSVs that accounts for this behavior. The source 104 must
determine whether Km and Km' match. However, they are secret
values, so they cannot be transmitted over the interface cable 102
for the DDC. Each device 104,106 feeds Km (or Km'), the random
number "A.sub.n", and the REPEATER bit into their respective HDCP
cipher engines in order for the transmitter 212 to verify that the
values match without sending them across the cable 213 for everyone
to see. The resulting data stream is split into three values:
[0199] R0/R0': This return value may be shared between the devices
104, 106 and is used to verify that authentication was
successful.
[0200] Ks/Ks': This value is kept private and is used as the
encryption session key for the HDCP cipher.
[0201] M0/M: This value is also kept private and is used in Part
Two of authentication (if the downstream device is a repeater
219).
[0202] The receiver sends R0' to the transmitter 212, which
compares it against its' own R0 value. If they match, that proves
that the sums Km and Km' matched, and authentication is successful.
Furthermore, the session keys Ks and K match, so the receiver 214
will be able to decrypt the content encrypted by the transmitter.
If Part One of authentication was successful, the transmitter 212
may begin sending encrypted content 202. If the downstream device
is a repeater 219, the repeater 219 must authenticate with its own
downstream device according to the same protocol. The transmitter
212 then starts a 5-second timer to allow for the repeater 219 to
perform Part Two of authentication. If Part Two fails or times out,
authentication fails and the transmitter 212 must stop transmitting
the protected content 202.
[0203] Authentication Part Two
[0204] Part Two of authentication only occurs if the downstream
device is a repeater 219. The purpose of Part Two is to inform the
source 104 of all downstream devices and the HDCP tree depth. The
source 104 uses this information to ensure that the tree topology
maximums have not been exceeded and to ensure that none of the
downstream devices have been revoked by DCP. The repeater 219 first
assembles a list of the KSVs of all downstream devices, as well as
the device count and the tree depth. The repeater 219 then passes
this information up to the source 104. To ensure that this
information hasn't been tampered with during transmission, each
device takes this list, appends its secret value M0/M0' from Part
One, and calculates a SHA-1 hash of the whole thing. The
transmitter 212 reads the hash result from the receiver 214 and
compares it against its own. If they match, Part Two of
authentication is successful.
[0205] Authentication Part Three
[0206] All HDCP devices are considered authenticated after
successful completion of Authentication Parts One and Two. Part
Three is simply a link integrity check to ensure that encryption is
in sync between all transmitter/receiver pairs 212, 214, 215, 216
in the tree. To support link integrity checks, the return values Ri
and Ri' roll over to a new value every 128 frames. Recall that the
initial Ri values R0 and R0' were generated during Part One of
authentication. Every two seconds, the transmitter 212 compares the
receiver's 216 Ri' value against its own Ri value to see if they
match. If they don't, encryption is out of sync and the receiver
216 cannot correctly decrypt the content 202. The user will see a
scrambled or "snowy" image on the screen. In this case the
transmitter 212 must restart authentication from the beginning.
[0207] The three part authentication process increases switching
delay when switching sources in a video distribution network.
Switching delay is the delay between switching an aspect of
incoming audiovisual data to a video sink, such as audiovisual data
source, audiovisual data resolution and audiovisual data refresh
rate, and the incoming audiovisual data being displayed on the
video sink. Not only must devices authenticate the HDCP link before
video transmission, each time an upstream HDCP link is switched,
downstream HDCP links may be affected as well because audiovisual
data transmission to downstream links is interrupted. Each time
video transmission is interrupted between an HDCP transmitter and
an HDCP receiver, the HDCP link fails Part Three of the
authentication process and the authentication process must be
restarted from Part One. This includes downstream connections that
were previously authenticated with each other.
[0208] For example, in a video distribution network comprising a
first HDCP-compliant video source and a second HDCP compliant video
source connected to an HDCP compliant video sink via an HDCP
compliant video switcher, when the video source transmitting HDCP
content to the video sink is switched from the first video source
to the second video source, not only must the second video source
authenticate with the video switcher, but the downstream link
between the video source and the video switcher must also be
re-authenticated due to the disruption in video transmission. This
despite the fact that the HDCP link between the video source and
the video switcher was already authenticated. This issue becomes
increasingly burdensome in expansive video distribution networks
with many layers (i.e. a large tree topology).
[0209] Additionally, when video transmission is interrupted between
an HDCP transmitter and an HDCP receiver due to upstream switching
and HDCP authentication, any downstream video scalers must lock
back on the incoming audiovisual data before outputting any scaled
audiovisual data. This introduces delay in addition to the delay
introduced by the HDCP authentication process. For example, each
time video transmission to a sink is interrupted, video scaler
internal to the sink will take anywhere between two and ten seconds
to lock onto the incoming audiovisual data again. Those skilled in
the art will recognize that scaler operation is unpredictable and
varies due to hardware and firmware specification. Often, video
scalers included in video sinks are not optimized for reducing
switching delay. Also unpredictable is video sink response while
embedded video scalers achieve video lock. Presented with
interrupted video, the video sink may display snow, pixilated
images, video artifacts or a blank screen while internal scaler
achieves video lock dependent on video sink manufacturer.
[0210] Because the HDCP authentication process operates in the
background, often unknown to the user, long switching delays are
unfairly blamed on video distribution components. Users may
experience the authentication process as a delayed period with snow
or disorienting video artifacts. This could result in undeserved
user dissatisfaction with the manufacturer of the components in the
video distribution network.
[0211] As will be explained below, aspects of the embodiments
describe systems, apparatuses and methods for reducing the
switching time in a video distribution network. Aspects of the
embodiments described herein provide for maintaining authentication
of downstream link during a switching discontinuity, minimizing the
interruption of video transmission resulting from switching events.
By outputting continuous video timing data to a sink over a
downstream HDCP link, even during switching discontinuities, the
downstream HDCP link satisfies the maintenance check in step three
of HDCP authentication. Accordingly, steps one and two of the HDCP
authentication protocol need not be repeated. Additionally, as a
result of maintaining the authentication of the HDCP link by
outputting continuous video timing data during switching
discontinuities, video scalers downstream of the HDCP link (i.e.,
internal video sink scalers) will not lose video lock with the
incoming video stream thereby reducing delay times further.
Finally, by outputting black frames of image data, the content
displayed during switching events is controlled.
[0212] FIG. 3 is a block diagram of an inventive switcher device
configured for reducing switching time in a video distribution
network. The video distribution network 300 is an HDCP system and
includes at least one source 104a, 104b, . . . , 104n (collectively
104) and at least one sink or display 106a, 106b, . . . , 106n
(collectively 106). At least two sources 104 include an HDCP
transmitter 212, such as an HDMI transmitter, configured to
transmit audiovisual data comprising video timing data and image
content data to the at least one sink 106. Each source 104 further
includes a graphic generator (not shown) to generate a graphic or
image. The HDCP transmitter 212 receives the HDCP content 202 from
an upstream content control function 210.
[0213] At least one sink includes an HDCP receiver, such as an HDMI
receiver. The source 104 determines via the authentication process
what content can be viewed, recorded, and shared based on
sinks/displays 106 that support HDCP and sinks/displays 106 that
does not support HDCP. The output of the source 104 is connected to
an input board 308 for a switcher device 302 through their
HDCP-protected interfaces 304 and the switcher device 302 serves as
an HDCP repeater for HDCP compliant content. An output board 310
for the switcher device 302 is connected to the input of the
sink/display 106 via another interface 102b. The interface 102a,
102b for the input board and the output board of the switcher
device 302 may be an HDMI cable that carries a variety of signals
such as one or more of TDMS, DDC, hot plug detect (HPD), and
RxSense, among others. As will be described later, the interface
102a, 102b for the input board and output board of the switcher
device 302 may also be a combination of one or more shielded
twisted pairs (STP) and one or more unshielded twisted pairs (UTP),
such as DigitalMedia (DM) cable available from Crestron
Electronics, Inc. of Rockleigh, N.J.
[0214] When an HDCP source 104 (more specifically source 104a)
detects an RxSense signal from an HDCP compliant sink/display 106
(more specifically sink/display 106a), the source 104a will
transmit HDCP content 202 to the sink/display 106a after the
authentication process is successful.
[0215] The audiovisual data 202 is encoded into three data
channels. These channels and a TMDS clock are carried over four
differential pairs from the source 104 to the sink/display 106. The
DDC is a communications interface similar to I2C. This interface
provides two-way communication in a master-slave relationship. The
upstream device 104 is the DDC master and the downstream device 106
is the DDC slave. The HDCP receiver indicates its presence to the
HDCP transmitter with the HPD signal. The HDCP transmitter 212 is
the HDCP Device most upstream, and receives the HDCP content 202
from an upstream content control function 210.
[0216] The switcher device 302, functioning as an HDCP repeater, is
a fully modular and expandable matrix switcher offering low-latency
digital video and audio switching, and HD lossless multi-room
signal distribution, for all types of A/V sources. The switcher
device 302 may be a Crestron Digital Media Switcher available from
Crestron Electronics, Inc. of Rockleigh, N.J.
[0217] The Crestron Digital Media Switcher is field-configurable to
handle, but not limited to, eight, sixteen, and thirty-two
audiovisual sources of virtually any type via input boards. The
outputs are also field-configurable to provide, but not limited to,
eight, sixteen, and thirty-two room outputs and/or HDMI outputs in
a single chassis. The chassis comprises slots for the insertion of
input and output boards. As will be described later, the input
boards and output boards may be input boards and output boards,
respectively, of the switcher device 302. Additionally, the input
boards and output boards may operate external of the chassis of the
Digital Media Switcher and be coupled to the Digital Media Switcher
via intermediate cards inserted into slots in the chassis.
[0218] The switcher device 302 includes a multiplexer 306 coupled
in-between the at least one input board 308a, 308b, 308n
(collectively 308) and at least one output board 310a, 310b, 310n
(collectively 310). The multiplexer 306 may be, but is not limited
to, a mechanical switch, electrically operated switch, solid state
relay, latching relay, reed relay, single-pole single-throw (SPST)
relay, single-pole double-throw (SPDT) relay, double-pole
single-throw (DPST) relay, and double-pole double-throw (DPDT)
relay.
[0219] The multiplexer 306 transmits an audiovisual data signal 202
from one of the at least two input boards 308 to a first output
board 310a. The multiplexer 306 dynamically switches between the
first input board 308a and at least a second input board 308b based
on a user control signal 316 that selects either the first video
source 104a or second video source 104b to be displayed on the
video sink 106a. The output board 310 is coupled to the at least
one sink/display 106 via an interface cable 102b. The interface
cable 102b may be an HDMI cable. The switcher 302 further includes
a processing unit 318 coupled to the multiplexer 306. The
processing unit 318 includes at least one transceiver 320 for
bidirectional communications with an end user device (e.g., 324,
326), in part, to receive the user control signal 316. The end user
device 324, 326 transmits the user control signal 316 from a touch
panel display 324 via a control system 322. An end user may also
transmit the user control signal 316 from a wireless device 326.
Software tools 328 may be loaded onto the wireless device and/or
touch panel 324 to assist the end user in selecting a desired
source 104 and the sink 106. In response to the user selecting the
desired source 104 for the sink 106, the end user device transmits
the user control signal 316 to the switcher device 302.
[0220] Upon the user selecting the desired source 104 for the at
least one desired display 106, the source 104 will authenticate
with the switcher device 302 as described above. The switcher
device 302 will authenticate with the at least one desired
downstream sinks 106 as described above. Once the authentication is
complete, the source 104 will transmit the HDCP content (i.e. HDCP
protected audiovisual data) via the HDCP link between the source
and the repeater. This HDCP link comprises the HDCP transmitter 212
of the source, an HDCP interface, and an HDCP receiver 214 of the
first input board 308a. The HDCP receiver of the input board 308a
receives the HDCP content and provides the audiovisual data
unencrypted to the multiplexer 306. The multiplexer 306, dependent
on the user control signal 316, routes the unencrypted audiovisual
data to the desired output board 310. The output board 310
processes and encrypts the audiovisual data and then transmits the
HDCP content to the desired sink 106 over an HDCP link between the
output board 310 and the video sink 106. The HDCP link between the
output board 310 and the video sink 106 comprises an HDCP
transmitter 215 of the output board, HDCP interface and HDCP
receiver of the video sink.
[0221] The multiplexer 306 is configured to dynamically route the
audiovisual data according to the user control signal received at
the processing unit 318. For example, a user viewing content from a
first source 104a, such as a cable tuner, may desire to switch to a
second source 104b, such as a Blu-ray disc player. When the
multiplexer 306 switches from routing audiovisual data from the
first source to routing audiovisual data from the second source
104b, the output board 310 experiences a switching delay as a
result of the delay caused by upstream HDCP authentication and
multiplexer 306 operation. A similar switching discontinuity may
also result from a change in resolution or change in refresh rate
of the received audiovisual data.
[0222] The output board 310 of the inventive switcher device 302 is
configured to continuously output audiovisual data including video
timing data and image content data during switching discontinuities
such that the HDCP link between the output board 310 and the video
sink 106 remains authenticated during the switch and an
aesthetically pleasing display is shown during said switch. For
example, the output board 310 may output black frames of
audiovisual data during switching discontinuities. Switching delay
in the video distribution network 300 is minimized by maintaining
the authentication of the HDCP link by continuously outputting
video timing data. Additionally, by continuously outputting video
timing data to the video sink during switching discontinuities,
video lock is maintained in video processing devices, such as
scalers, downstream from the output board 310 (i.e. scalers
internal to video sink), thereby further minimizing switching
delay.
[0223] FIG. 4 is a block diagram of a portion of the switcher
device 302 shown in FIG. 3. The output board 310a further comprises
a receiver 401, an output scaler 402, an output processing unit 403
and an HDCP transmitter 215. The receiver 401 is configured to
receive audiovisual data routed from the first input board 308a or
second input board 308b via the multiplexer 306. As described
below, according to aspects of the embodiments, the receiver 401 is
an HDCP receiver configured for receiving HDCP encrypted
content.
[0224] The output scaler 402 receives the audiovisual data from the
receiver 401 and is adapted to convert the received audiovisual
data to a native resolution of the video sink 106. The output board
310 may receive the native resolution of the video sink 106 via an
EDID channel. Those skilled in the art will recognize that the
operation of video scalers embedded in end user devices are
idiosyncratic depending on manufacturer and may perform
substantially below par, resulting in poor video quality and
delayed performance. By converting to the native resolution of the
video sink 106, video processing is minimized in downstream
embedded video scalers.
[0225] According to aspects of the embodiments, the output scaler
402 of the output board 310 is adapted for operating in a pass
through mode in which the output scaler detects the resolution of
the incoming audiovisual data via the video timing data. The output
scaler passes the incoming audiovisual data through to the HDCP
transmitter if the audiovisual data is routed to the output board
already at a native resolution of the video sink.
[0226] The output scaler 402 is further adapted to generate
audiovisual data comprising video timing data and image content
data during switching discontinuities. For example, during a
switching discontinuity between receiving audiovisual data from a
first source 104a and audiovisual data from a second source 104b,
the output scaler 402 may output black frames. By outputting a
continuous stream of audiovisual data, more specifically video
timing data, to the HDCP transmitter 215, the HDCP link between the
output board 310 and the source is maintained as authenticated
during the switch. In addition, by outputting black frames of
audiovisual data, more specifically image content data, the end
user experiences a clean transition from the first source 104a to
the second source 104b. According to aspects of the embodiments,
the output scaler 402 may generate frames of image content data of
a color other than black, or may generate image content data
comprising an image, such as a corporate logo.
[0227] According to aspects of the embodiments, prior to outputting
audiovisual data from the second source 104b, the output scaler 402
must receive a sufficient amount of audiovisual data from the
second source 104b. This is known as achieving video lock.
Following a switching discontinuity, the output scaler 402 is
further adapted to generate image content data until video lock is
achieved. By generating image content data until the output scaler
402 achieves video lock, the user is presented with a clean
transition during switching events.
[0228] The output scaler 402 is adapted to operate in a free run
mode by automatically generating video timing data during switching
discontinuities.
[0229] The output scaler 402 is adapted to generate image content
data in response to control signals from the output processing unit
403. Upon receiving the user control signal to switch the source of
audiovisual data and prior to transmitting a switching signal to
the multiplexer 306, the switcher processing unit 318 transmits a
prepare signal to the output processing unit 403. The output
processing unit 403 in turn instructs the output scaler 402 to
generate black frames of audiovisual data.
[0230] The HDCP transmitter 215, such as an HDMI transmitter,
converts and encodes the audiovisual data output from the output
scaler 402 to one or more TMDS signals for transmission to the
video sink 106 over the HDCP interface. According to aspects of the
embodiments, the HDMI transmitter comprises an HDCP transmitter
chip and may further comprise TMDS encoders or decoders and other
HDMI-specific features. The audiovisual data is re-encrypted in
accordance with the shared secret from authentication between the
HCDP repeater and the HDCP sink. The HDCP transmitter 215 receives
the native resolution and the native refresh of the sink via a
display data channel (DDC) of the interface. The HDCP interface
between transmitter and the HDCP receiver may be HDMI.
[0231] FIG. 5 shows the switcher device 302 in a video distribution
network 300, according to further aspects of the embodiments in
which the output board 310 is contained in a housing external to
the switcher device 302. The video distribution network 300
comprises an extended transmission board 510 coupled between the
multiplexer 306 and the output board 310. The video distribution
network 300 further comprises an extended reception board 508.
According to aspects of the embodiments, the extended reception
board 508 and extended transmission board 510 may be modular input
and output boards, respectively, configured to be inserted into the
switcher device 302. As described below, the extended transmission
and reception boards allow for extended cable lengths that
increases the functionality of the video distribution network 300.
For example, the output board 310 may be collocated in the same
area as its corresponding video sink 106. The switcher device 302
may be remotely located in a central location or out of view, such
as in an equipment closet. Similarly, the first input board 308a
and second input board 308b may be collocated with the first video
source 104a and the second video source 104b, respectively.
[0232] According to aspects of the embodiments, the output board
310 is adapted for receiving encrypted audiovisual data via an HDCP
link. The extended transmission board 510 is communicatively
coupled between the multiplexer 306 and the output board 310 and is
adapted for encrypting the audiovisual data routed by the
multiplexer 306 and transmitting the encrypted audiovisual data to
the output board 310 via an HDCP link. The HDCP link comprises an
HDCP transmitter 615 of the extended transmission board 510, an
HDCP interface 502 and an HDCP receiver 401 of the output board
310. The HDCP interface 502 may be one or more pairs of twisted
cable or fiber optical cable, such as DigitalMedia cable available
from Crestron Electronics, Inc. of Rockleigh N.J. Those skilled in
the art will recognize that DigitalMedia cable is a
multi-generational family of interface cables particularly designed
for media transmission for extended lengths.
[0233] Within a single plenum-rated jacket, original DigitalMedia
cable contains one high-bandwidth/low-crosstalk shielded 4-twisted
pair (STP) cable, one CAT5e unshielded 4-twisted pair (unshielded
twisted pair (UTP)) cable, and one DMNet cable. The STP
"Audiovisual data" cable is of a specialized construction designed
to allow the longest possible cable lengths for transporting
high-definition digital video and audio. The Cat5e "Data
Management" cable carries high-speed Ethernet and other data, plus
5V direct current (DC) power. Finally, the DMNet cable carries
additional proprietary control signals and 24V DC power. Original
DigitalMedia cable is rated for up to 220 ft of audiovisual
transmission.
[0234] FIG. 6 is a block diagram of the extended transmission board
and the output board shown in FIG. 5, according to aspects of the
embodiments. The block diagram of the output board 310 is similar
to the block diagram of the output board 310 in FIG. 4, with the
exception being that in FIG. 5, the receiver 401 is an HDCP
receiver configured for receiving HDCP content over an HDCP
interface 502. The extended transmission board 510 comprises a
receiver 601 and an HDCP transmitter 615.
[0235] FIG. 7 is a flowchart illustrating steps of method 700 for
reducing the switching time in a video distribution network 300,
according to aspects of the embodiments.
[0236] In step 701, a switcher device 302 receives audiovisual data
at a first input board 308a via an HDCP link between a first video
sink 106a and the first input board 308a.
[0237] In step 702, the switcher device 302 routes audiovisual data
from the first input board 308a to an output board 310a.
[0238] In step 704, the output board 310 transmits audiovisual data
to a video sink 106 over a security protocol link. According to
aspects of the embodiments, the output board 310 scales the
audiovisual data received from the first input board 308a to the
native resolution of the video sink 106 (step 703) prior to
transmitting to the video sink 106.
[0239] In step 705, the processing unit 318 of the switcher device
302 receives a control signal to switch from routing audiovisual
data from the first input board 308a to routing audiovisual data
from the second input board 308b.
[0240] According to aspects of the embodiments, the switcher device
processing unit 318 transmits a prepare signal to the output board
310a, indicating that there will be a switching discontinuity (step
706).
[0241] According to aspects of the embodiments, the output board
310a generates image content data, such as black frames of video,
in response to receiving the prepare signal from the switcher
device processing unit 318 (step 707). The scaler 402 outputs the
generated image content data rather than the live image content
data being routed to the output board 310a from the multiplexer
306.
[0242] In step 708, the multiplexer 306 ceases routing audiovisual
data from the first input board 308a.
[0243] In step 709, the output board 310 continues generating video
timing data at a native resolution during the delay between
receiving audiovisual data from the first input board 308a and
receiving audiovisual data from the second input board 308b. By
outputting a continuous stream of video timing data, the output
board 310a maintains the authenticity of the security link between
the output board 310a and the video sink 106.
[0244] In step 710, the switcher device 302 receives audiovisual
data at a second input board 308b via an HDCP link between a second
video sink 106b and the second input board 308b.
[0245] In step 711, the switcher device 302 routes audiovisual data
from the second input board 308b to the output board 310a.
[0246] Following step 711 is decision step 715. In decision step
715, it is determined whether video lock has occurred. If video
lock has occurred ("Yes" path from decisions step 715), method 700
proceeds to step 713. If video lock has not occurred ("No" path
from decision step 715), method 700 proceeds to step 712, and
continues to monitor video data to determine if video lock has
occurred.
[0247] In step 712, the output board continues generating and
outputting image content data (i.e. black frames of video) until
video lock is achieved.
[0248] In step 714, the output board 310a transmits live image
content data routed from the second input board 308a to the video
sink 106 over an HDCP link. According to aspects of the
embodiments, the output board 310a scales the audiovisual data
received from the first input board 308a to the native resolution
of the video sink 106 (step 713) prior to transmitting to the video
sink 106.
[0249] The following is a pseudo-code representation of the
operation in accordance with aspects of the embodiments.
[0250] Detect a user control signal to switch from a first video
source to a second video source.
[0251] Transmit a prepare signal to a processing unit of an output
board in response to the detection of the user control signal.
[0252] Detect the prepare signal at the output boar.
[0253] Instruct scaler to generate image content data.
[0254] Cease routing audiovisual data from a first video source to
the output board.
[0255] Continue generating video timing data at the scaler of the
output board.
[0256] Begin routing audiovisual data from a second video source to
the input board.
[0257] Cease generating image content data upon achieving video
lock.
[0258] According to aspects of the embodiments, the video
distribution system leverages a backdoor communication bus to
prepare downstream devices, such as an output board 310 internal to
the switcher device 302 or external to the switcher device 302, for
a switching event.
[0259] Prior to a switching event, the switcher processing unit 318
transmits a prepare signal to downstream devices to prepare for a
switching event. Each downstream device then relays the prepare
signal to their downstream devices until the prepare signal is
received at each necessary output board 310. For example,
downstream devices may comprise additional switcher devices, output
boards or intermediary relay devices, and output boards 310 may
comprise output boxes and output cards outputting audiovisual data
to a video sink.
[0260] Output scalers 402 in the output boards 310 then "freeze"
the current video in anticipation of the switch by ceasing
transmission of scaled live audiovisual data to the sink and
instead generate and output audiovisual data comprising a repeated
frame of image content data. The repeated frame of image content
data may be a frame of image content data received from the first
audiovisual source prior to the switching event. By generating a
repeated frame of image content data from the first audiovisual
source, the video displayed on the video sink will appear to have
momentarily frozen.
[0261] The switcher processing unit 318 directs the multiplexer 306
to perform the switching event subsequent to transmission of the
prepare signal. The switcher processing unit 318 may direct the
multiplexer 306 to perform the switch upon a predefined amount of
time after transmitting the prepare signal or may direct the
multiplexer 306 subsequent to confirming reception of the prepare
signal.
[0262] The output scaler 402 generates and outputs the repeated
frame of image content data until it has achieved video lock with
the audiovisual data it receives subsequent to the switching event.
By freezing and then unfreezing the video displayed on the video
sink, the output scaler 402 achieves the look of an "instant
switch" which is aesthetically pleasing to viewers and provides the
perception of an instantaneous switch. According to aspects of the
embodiments, while the video system may distribute secure content,
such as HDCP protected content, the content does not necessarily
need be protected content.
[0263] FIG. 8 shows a block diagram of a portion of the switcher
device, according to aspects of the embodiments. The multiplexer
306 transmits an audiovisual data signal from the first input board
to a first output board 310a. The multiplexer 306 dynamically
switches between the first input board and a second input board
based on a user control signal that selects either the first video
source or second video source to be displayed on the video
sink.
[0264] The output board may be a card configured for being inserted
into the switcher device or may be external to the switcher device.
According to aspects of the embodiments, there may be one or more
intermediary devices between the multiplexer 306 and the output
board such as additional switcher devices and relay devices as
shown in the video distribution system of FIG. 10. The output board
comprises a receiver, an output scaler 402, an output processing
unit 403 and a transmitter 215. As discussed above, the transmitter
215 may be an HDCP transmitter. The receiver 401 is configured to
receive audiovisual data routed from the first input board or
second input board via the multiplexer 306. The receiver may be an
HDCP receiver configured for receiving HDCP encrypted content.
[0265] The output scaler 402 receives the audiovisual data from the
receiver and is configured to convert the received audiovisual data
to a native resolution of the video sink. The output board may
receive the native resolution of the video sink via an EDID
channel. Those skilled in the art will recognize that the operation
of video scalers embedded in end user devices are idiosyncratic
depending on manufacturer and may perform substantially below par,
resulting in poor video quality and delayed performance. By
converting to the native resolution of the video sink, video
processing is minimized in downstream embedded video scalers.
[0266] According to aspects of the embodiments, the output scaler
402 of the output board 310 is adapted for operating in a pass
through mode in which the output scaler 402 detects the resolution
of the incoming audiovisual data via the video timing data. The
output scaler 402 passes the incoming audiovisual data through to
the transmitter 215 if the audiovisual data is routed to the output
board 310 already at a native resolution of the video sink.
[0267] The output scaler 402 is further adapted to generate
audiovisual data comprising video timing data and image content
data prior to and during switching discontinuities. The output
scaler 402 may further comprise a memory buffer and a frame buffer
for generating and outputting a repeated frame of video to the
video sink.
[0268] According to aspects of the embodiments, prior to and during
a switching discontinuity from a switching event, the output scaler
402 may output a repeated frame of image content data from the
audiovisual data received from the first source. For example, upon
receiving the prepare signal from the multiplexer 306, the output
scaler 402 will "freeze" the video displayed on the video sink by
generating and outputting a repeating frame of image content data
from the audiovisual data received from the first source. The
output scaler 402 is configured for continuing to generate and
output audiovisual data comprising video timing data and the
repeated frame of image content data while the switcher device
ceases routing audiovisual data from the first video source and
begins routing audiovisual data from the second video source.
[0269] The output scaler 402 must receive a sufficient amount of
audiovisual data from the second source 104b prior to outputting
live audiovisual data from the second source 104b. This is known as
achieving video lock. Following a switching discontinuity, the
output scaler 402 is further configured to generate the video
timing data and repeated frame of image content data until video
lock is achieved. Upon achieving video lock with the incoming video
after the switching discontinuity, the output scaler 402 will then
"unfreeze" the video by ceasing outputting the repeating frame and
instead outputting the live scaled video. By repeating a frame of
video, the user is presented a cleaner and more aesthetically
pleasing switch consisting of a momentarily, and in some instances
imperceptible, frozen screen.
[0270] In addition to the aesthetic advantages and perceived
reduction in switching time by the user, aspects of the embodiments
reduce the switching time by maintaining scaler lock in any
downstream scalars such as scalars embedded in video sinks. In HDCP
systems switching time is further minimized. By outputting a
continuous stream of audiovisual data, more specifically video
timing data, to the HDCP transmitter 215, the HDCP link between the
output board and the source is maintained as authenticated during
the switch.
[0271] The output scaler 402 is adapted to generate image content
data in response to control signals from the output processing unit
403. The communication interface between the switcher processing
unit 318 and the output processing unit 403 may be an Ethernet
interface. According to aspects of the embodiments, the prepare
signal may be a user datagram protocol (UDP) packet transmitted
over the Ethernet interface. However, aspects of the embodiments
are not limited to UDP packets transmitted over Ethernet. In other
aspects of the embodiments, the interface may be a serial
peripheral interface (SPI) or may be an HDMI interface transmitting
the prepare signal as an info-frame packet.
[0272] Upon receiving the user control signal to initiate a
switching event and prior to transmitting a switching signal to the
multiplexer 306, the switcher processing unit 318 transmits a
prepare signal to the output processing unit 403 via a
communication interface. The output processing unit 403 in turn
instructs the output scaler 402 to generate a repeated frame of
audiovisual data.
[0273] According to aspects of the embodiments, the switcher
processing unit 318 may broadcast the prepare signal to each
connected downstream device. Each downstream device may in turn
process and broadcast the prepare signal to each of its connected
downstream devices. As will be discussed below, in further aspects
of the embodiments, the switcher processing unit 318 may transmit
directly to each necessary output scaler 402. The prepare signal
may comprise an address, such as a network address of an output
card or output box.
[0274] The transmitter 215 is configured for converting and
encoding the audiovisual data from the output scaler 402 for
transmission to the video sink. According to aspects of the
embodiments, the transmitter 215 is an HDCP transmitter 215. The
HDCP transmitter 215, such as an HDMI transmitter 215, converts and
encodes the audiovisual data output from the output scaler 402 to
one or more TDMS signals for transmission to the video sink over
the HDCP interface. According to aspects of the embodiments, the
HDMI transmitter 215 comprises an HDCP transmitter 215 chip and may
further comprise TMDS encoders or decoders and other HDMI-specific
features. The audiovisual data is re-encrypted in accordance with
the shared secret from authentication between the HCDP repeater and
the HDCP sink. The HDCP transmitter 215 receives the native
resolution and the native refresh of the sink via a DDC of the
interface. The HDCP interface between transmitter 215 and the HDCP
receiver may be HDMI.
[0275] FIG. 9 is a flowchart illustrating steps to perform method
900 for reducing the switching time in a video distribution
network, according to aspects of the embodiments.
[0276] In step 901, a switcher device receives audiovisual data at
a first input board via an AV link between a first video sink and
the first input board.
[0277] In step 902, the switcher device routes audiovisual data
from the first input board to an output board.
[0278] In step 904, the output board transmits audiovisual data to
a video sink over an AV link. According to aspects of the
embodiments, the output board scales the audiovisual data received
from the first input board to the native resolution of the video
sink (step 903) prior to transmitting to the video sink.
[0279] In step 905, the processing unit 318 of the switcher device
receives a control signal to switch from routing audiovisual data
from the first input board to routing audiovisual data from the
second input board.
[0280] In step 906, the switcher device processing unit 318
transmits a prepare signal to the output board, indicating that
there will be a switching discontinuity.
[0281] In step 907, the output board generates image content data,
such as a repeating frame of video, in response to receiving the
prepare signal from the switcher device processing unit 318. The
output scaler 402 outputs the generated image content data rather
than the live image content data being routed to the output board
from the multiplexer 306.
[0282] In step 908, the multiplexer 306 ceases routing audiovisual
data from the first input board.
[0283] In step 909, the output board continues generating video
timing data at a native resolution during the delay between
receiving audiovisual data from the first input board and receiving
audiovisual data from the second input board. By outputting a
continuous stream of video timing data, the output board may
maintain the authenticity of any security link between the output
board and the video sink.
[0284] In step 910, the switcher device receives audiovisual data
at a second input board via an AV link between a second video sink
and the second input board.
[0285] In step 911, the switcher device routes audiovisual data
from the second input board to the output board.
[0286] Following step 911 is decision step 915. In decision step
915, it is determined whether video lock has occurred. If video
lock has occurred ("Yes" path from decision step 915), method 900
proceeds to step 913. If video lock has not occurred ("No" path
from decision step 915), method 900 proceeds to step 912. In step
912, the output board continues generating and outputting image
content data (i.e. repeating frame of video) until video lock is
achieved.
[0287] In step 914, the output board transmits live image content
data routed from the second input board to the video sink over an
AV link. According to aspects of the embodiments, the output board
scales the audiovisual data received from the first input board to
the native resolution of the video sink (step 913) prior to
transmitting to the video sink.
[0288] The following is a pseudo-code representation of the
operation in accordance with aspects of the embodiments.
[0289] Detect a user control signal to switch from a first video
source to a second video source.
[0290] Transmit a prepare signal to a processing unit of an output
board in response to the detection of the user control signal.
[0291] Detect the prepare signal at the output board.
[0292] Instruct output scaler to generate a repeated frame of image
content data.
[0293] Cease routing audiovisual data from a first video source to
the output board.
[0294] Continue generating video timing data at the output scaler
of the output board.
[0295] Begin routing audiovisual data from a second video source to
the input board.
[0296] Cease generating image content data upon achieving video
lock.
[0297] According to aspects of the embodiments, the switcher device
processing unit 318 is adapted to determine the network topology of
the video distribution network and transmitting an addressed
prepare signal to each desired output device.
[0298] Certain video distribution networks, such as those employed
on corporate campuses or educational institutions, may comprise one
or more switcher devices 302 connected in a complex topology. In
addition to being coupled to one or more output boards 310 (i.e.
output cards 310a, output boxes 310b), a switcher device 302 may be
communicatively coupled with one or more switcher devices 302 to
extend the reach and breadth of the video distribution network. In
addition, a single AV source may be routed to more than one AV
sink. For example, an AV source may be displayed in multiple
conference rooms of a corporate facility. In this example, a
switcher device may have to route audiovisual data from the
multiplexer 306 to more than one output board 310.
[0299] FIG. 10 is a diagram of a video distribution network
according to aspects of the embodiments. The video distribution
network 1000 comprises a plurality of cascaded switcher devices
302. According to aspects of the embodiments, an output of a first
switcher device 302a is coupled to an input of a second switcher
device 302b and an output of the second switcher device 302b is
coupled to an input of a third switcher device 302c.
[0300] Each successive device adds delay to the switching times
during a switching event. Consider, as an example, video
distribution network 1000 in which the first switcher device 302a
receives audiovisual data at a first input card and routes to a
video sink 106e via an output card coupled to a second switcher
device 302b and third switcher device 302c and an output box 310e.
According to aspects of the embodiments in which the first switcher
device processing unit 318 transmits a prepare signal to each of
its endpoints (i.e. 310a, 510a . . . 510b), which then process and
transmit to each of their endpoints until it reaches the desired
endpoint, a noticeable delay will have been introduced to the
switching process.
[0301] To reduce the delay caused by transmission of the prepare
signal, according to aspects of the embodiments, each switcher
device is adapted to determine and store the topology of the video
distribution network. The switcher devices may determine the
topology upon being employed in the video distribution network,
upon other devices joining or leaving the video distribution
network, at periodic time intervals, or at any other time. The
switcher device may determine the topology of the video
distribution network via a network scanning tool or other similar
technology.
[0302] Upon receiving the control signal to initiate a switching
event and prior to transmitting a switch command to the multiplexer
306, the switching processing unit 318 transmits a prepare signal
addressed to one or more desired endpoints. A desired endpoint is
each endpoint comprising a scalar and transmitting audiovisual data
to desired sinks. The endpoint may comprise an output board, such
as an output card or an output box.
[0303] While the switcher processing unit 318 must still transmit
via intermediary devices, the switcher processing unit 318 need not
broadcast to all downstream devices. Advantageously, the prepare
signal does not have to be processed at each intermediary node in
the network which reduces latencies and reduces bandwidth.
[0304] FIG. 11 is a flowchart illustrating steps of method 1100 for
reducing the switching time in a video distribution network 300,
according to aspects of the embodiments.
[0305] In step 1101, switcher device 302 receives audiovisual data
at a first input board via an AV link between a first video sink
and the first input board.
[0306] In step 1102, the switcher device 302 routes audiovisual
data from the first input board to an output board. The output
board may be coupled via intermediate devices such as other
switcher devices and output boards.
[0307] In step 1104, the output board transmits audiovisual data to
a video sink over an AV link. According to aspects of the
embodiments, the output board scales the audiovisual data received
from the first input board to the native resolution of the video
sink (step 1103) prior to transmitting to the video sink.
[0308] In step 1105, the processing unit 318 of the switcher device
302 receives a control signal to switch from routing audiovisual
data from the first input board to the output board to routing
audiovisual data from the second input board to the output
board.
[0309] In step 1106, the switcher device processing unit 318
determines the path to the output board including an output of the
switcher device 302 and a network address of the output board from
a stored network topology. Using the above example, in regard to
FIG. 10, to first switcher device 302a may determine that the path
to an endpoint comprises a third output board of the switcher
device.
[0310] In step 1107, the switcher device processing unit 318
transmits a prepare signal comprising the network address of the
output board to the output board, indicating that there will be a
switching event. The switcher device transmits the addressed
prepare signal to the appropriate downstream node according to the
topology.
[0311] In step 1108, the output board generates image content data,
such as a repeating frame of video, in response to receiving the
prepare signal from the switcher device processing unit 318. Upon
receiving the prepare signal, the output scaler 402 may freeze on a
frame of video by continuously outputting that frame.
[0312] The output scaler 402 outputs the generated image content
data rather than the live image content data being routed to the
output board from the multiplexer 306.
[0313] In step 1109, the multiplexer 306 ceases routing audiovisual
data from the first input board.
[0314] In step 1110, the output board continues generating video
timing data at a native resolution during the delay between
receiving audiovisual data from the first input board and receiving
audiovisual data from the second input board. By outputting a
continuous stream of video timing data, the output board maintains
the authenticity of the security link between the output board and
the video sink.
[0315] In step 1111, the switcher device receives audiovisual data
at a second input board via an AV link between a second video sink
and the second input board.
[0316] In step 1112, the switcher device routes audiovisual data
from the second input board to the output board.
[0317] Following step 1112 is decision step 1116. In decision step
1116, it is determined whether video lock has occurred. If video
lock has occurred ("Yes" path from decision step 1116), method 1100
proceeds to step 1114. If video lock has not occurred ("No" path
from decision step 1116), method 1100 proceeds to step 1113. In
step 1113, the output board continues generating and outputting
image content data (i.e. repeating frame of video) until video lock
is achieved.
[0318] In step 1115, the output board transmits live image content
data routed from the second input board to the video sink over an
AV link. According to aspects of the embodiments, the output board
scales the audiovisual data received from the first input board to
the native resolution of the video sink (step 1114) prior to
transmitting to the video sink.
[0319] The following is a pseudo-code representation of the
operation in accordance with aspects of the embodiments.
[0320] Detect a user control signal to switch from a first video
source to a second video source.
[0321] Determine network address of a desired output card.
[0322] Transmit a prepare signal comprising network address to a
processing unit 403 of the desired output board in response to the
detection of the user control signal.
[0323] Detect the prepare signal at the output board.
[0324] Instruct scaler to generate a repeated frame of image
content data.
[0325] Cease routing audiovisual data from a first video source to
the output board.
[0326] Continue generating video timing data at the scaler of the
output board.
[0327] Begin routing audiovisual data from a second video source to
the input board.
[0328] Cease generating image content data upon achieving video
lock.
[0329] FIG. 12 shows a block diagram of the output scaler,
according to aspects of the embodiments. The output scaler
comprises a frame rate processing block 1202, a memory further
comprising a frame buffer 1204, an input scaling block 1206 and an
output scaling block 1208. According to aspects of the embodiments,
the term block is synonymous with circuit.
[0330] The scaler receives input audiovisual data 1201 from the
receiver comprising video timing data and image content data. The
frame rate processing block is adapted to receive the asynchronous
input video timing data 1201 and write the incoming image content
data into memory 1204. The frame rate processing block 1202 is
further adapted to receive the free-running output video timing
data 1211 and read incoming video data from memory 1204 as required
by the output resolution of the scaler 402 (i.e. native resolution
of the video sink). The frame rate processing block 1202 is further
adapted to perform frame rate conversion if the input refresh rate
and the output refresh rate of the audiovisual data differ.
[0331] The input scaling block 1206 is adapted to receive the
asynchronous input video timing data and perform scaling if
required. In certain applications depending on the input and output
setups, input scaling can be performed prior to frame rate
processing according to aspects of the embodiments. According to
further aspects of the embodiments, output scaling can be performed
subsequent to frame rate processing. In these applications, the
output scaling block 1208 receives the free running output video
timing data and performs scaling if required.
[0332] The free running output timing generator 1210 is adapted to
continuously generate free running output video timing data 1211
used to give the downstream video sink a fixed resolution.
[0333] According to aspects of the embodiments in which the output
scaler 402 generates audiovisual data comprising a repeated frame
of image content data, the last frame of video received by the
output scaler 402 (i.e. the frame to be repeated), is repeatedly
read from the memory and frame buffer and output by the output
scaler 402. Upon the output scaler 402 achieving scaler lock with
audiovisual data from the second source, a frame of image content
data from audiovisual data received from the second source is read
from the memory and frame buffer and output by the output scaler
402.
[0334] Any process descriptions or blocks in flow charts should be
understood as representing modules, segments or portions of code
that include one or more executable instructions for implementing
specific logic functions or steps in the process. Alternate
implementations are included within the scope of the aspects of the
embodiments in which functions can be executed out of order from
that shown or discussed, including substantial concurrence or
reverse order, depending on the functionality involved, as would be
understood by those of skill in the art. Also, steps disclosed as
separate may be performed concurrently or combined, and a step
shown as discrete may be performed as two or more steps.
Furthermore, numerical values and disclosures of specific hardware
are illustrative rather than limiting. Moreover, while the
preferred embodiment has been disclosed in the context of HDMI,
aspects of the embodiments can be implemented for use with another
suitable interface that uses HDCP, such as DVI or any substantially
HDMI-like interface. Therefore, aspects of the embodiments should
be construed as limited by only the appended claims.
[0335] In this description, various functions and operations can be
described as being performed by or caused by software code to
simplify description. However, those skilled in the art will
recognize what is meant by such expressions is that the functions
result from execution of the code by a processor or processing
unit, such as a microprocessor. Alternatively, or in combination,
the functions and operations can be implemented using special
purpose circuitry, with or without software instructions, such as
using application-specific integrated circuit (ASIC) or
field-programmable gate array (FPGA). Embodiments can be
implemented using hardwired circuitry without software
instructions, or in combination with software instructions. Thus,
the techniques are limited neither to any specific combination of
hardware circuitry and software, nor to any particular source for
the instructions executed by the data processing system.
[0336] While some embodiments can be implemented in fully
functioning computers and computer systems, various embodiments are
capable of being distributed as a computing product in a variety of
forms and are capable of being applied regardless of the particular
type of machine of computer-readable media used to actually effect
the distribution.
[0337] At least some aspects disclosed can be embodied, at least in
part, in software. That is, the techniques may be carried out in a
computer system or other data processing system in response to its
processor/processing unit, such as a microprocessor, executing
sequences of instructions contained in a memory, such as ROM,
volatile RAM, non-volatile memory, cache or a remote storage
device.
[0338] Routines executed to implement the embodiments can be
implemented as part of an operating system, middleware, service
delivery platform, software development kit (SDK) component, web
services, or other specific application, component, program,
object, module or sequence of instructions referred to as "computer
programs". Invocation interfaces to these routines can be exposed
to a software development community as an application programming
interface (API). The computer programs typically comprise one or
more instructions set at various times in various memory and
storage devices in a computer, and that, when read and executed by
one or more processors/processing units in a computer, cause the
computer to perform operations necessary to execute elements
involving the various aspects.
[0339] A machine readable medium can be used to store software and
data which when executed by a data processing system causes the
system to perform various methods. The executable software and data
can be stored in various places, including for example ROM,
volatile RAM, non-volatile memory and/or cache. Portions of this
software and/or data can be stored in any of these storage devices.
Further, the data and instructions can be obtained from centralized
servers or peer to peer networks. Different portions of the data
and instructions can be obtained from different centralized servers
and/or peer-to-peer networks. Different portions of the data and
instructions can be obtained from different communication sessions
or in a same communication session. The data and instructions can
be obtained in their entirety prior to the execution of the
applications. Alternatively, portions of the data and instructions
can be obtained dynamically, just in time, when needed for
execution. Thus, it is not required that the data and instructions
be on a machine readable medium in entirety at a particular
instance of time.
[0340] Examples of computer-readable media include, but are not
limited to, recordable and non-recordable type media, such as
volatile and non-volatile memory devices, read-only memory (ROM),
random access memory (RAM), flash memory devices, floppy and other
removable disks, magnetic disk storage media, optical storage media
(e.g. compact disc read-only memory (CD ROM), digital versatile
discs (DVDs), etc.) among others. The instructions may be embodied
in digital and analog communication links for electrical, optical,
acoustical or other forms of propagated signals, such as carrier
waves, infrared signals, digital signals, etc.
[0341] In general, a machine readable medium includes any mechanism
that provides (i.e. stores and/or transmits) information in a form
accessible by a machine (e.g. a computer, network device, personal
digital assistant, manufacturing tool, any device with a set of one
or more processors, etc.).
[0342] In various embodiments, hardwired circuitry can be used in
combination with software instructions to implement the techniques.
Thus, the techniques are neither limited to any specific
combination or hardware circuitry and software nor to any
particular source for the instructions executed by the data
processing system.
[0343] Although some of the drawings illustrate a number of
operations in a particular order, operations that are not order
dependent can be reordered and other operations can be combined, or
broken out. While some reordering or other groupings are
specifically mentioned, others will be apparent to those of
ordinary skill in the art and so do not present an exhaustive list
of alternatives. Moreover, it should be recognized that the stages
could be implemented in hardware, firmware, software or any
combination thereof.
[0344] Although aspects of the embodiments have been described
herein with reference to the accompanying drawings, it is to be
understood that the aspects of the embodiments are not limited to
those precise embodiments, and that various other changes and
modifications may be made therein by one skilled in the art without
departing from the scope of the appended claims.
INDUSTRIAL APPLICABILITY
[0345] To solve the aforementioned problems, aspects of the
embodiments are directed towards a unique device in which an output
board with an output scaler 402 minimizes switching delay in a
video distribution network by outputting a continuous stream of
audiovisual data during switching events.
ALTERNATE EMBODIMENTS
[0346] Alternate embodiments may be devised without departing from
the spirit or the scope of the aspects of the embodiments. For
example, during switching events, the output scaler can generate
video information such that a switching graphic will be displayed
on the screen or a color other than black.
* * * * *