WO2006044547A2 - Speeding up channel change - Google Patents
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- WO2006044547A2 WO2006044547A2 PCT/US2005/036834 US2005036834W WO2006044547A2 WO 2006044547 A2 WO2006044547 A2 WO 2006044547A2 US 2005036834 W US2005036834 W US 2005036834W WO 2006044547 A2 WO2006044547 A2 WO 2006044547A2
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/41—Structure of client; Structure of client peripherals
- H04N21/426—Internal components of the client ; Characteristics thereof
- H04N21/42607—Internal components of the client ; Characteristics thereof for processing the incoming bitstream
- H04N21/4263—Internal components of the client ; Characteristics thereof for processing the incoming bitstream involving specific tuning arrangements, e.g. two tuners
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/41—Structure of client; Structure of client peripherals
- H04N21/426—Internal components of the client ; Characteristics thereof
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/438—Interfacing the downstream path of the transmission network originating from a server, e.g. retrieving encoded video stream packets from an IP network
- H04N21/4383—Accessing a communication channel
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- H—ELECTRICITY
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- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/438—Interfacing the downstream path of the transmission network originating from a server, e.g. retrieving encoded video stream packets from an IP network
- H04N21/4383—Accessing a communication channel
- H04N21/4384—Accessing a communication channel involving operations to reduce the access time, e.g. fast-tuning for reducing channel switching latency
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/44—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs
- H04N21/4405—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs involving video stream decryption
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- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/45—Management operations performed by the client for facilitating the reception of or the interaction with the content or administrating data related to the end-user or to the client device itself, e.g. learning user preferences for recommending movies, resolving scheduling conflicts
- H04N21/462—Content or additional data management, e.g. creating a master electronic program guide from data received from the Internet and a Head-end, controlling the complexity of a video stream by scaling the resolution or bit-rate based on the client capabilities
- H04N21/4623—Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/50—Tuning indicators; Automatic tuning control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/162—Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
- H04N7/163—Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing by receiver means only
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- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
- H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
Definitions
- the present invention pertains generally to the area of digital television systems.
- the invention provides a method and apparatus to enhance channel changes at a user display in a digital television network.
- a set-top box At the center of digital television communication is a set-top box (STB), which receives the broadcast content and connects to a television set and typically sits on top of it.
- the STB runs software referred to as middleware, consisting of computer programs which control the flow of broadcast programs and internet traffic as well as data from the viewer.
- middleware consisting of computer programs which control the flow of broadcast programs and internet traffic as well as data from the viewer.
- the STB must be able to handle the bi ⁇ directional data flow.
- Much effort has been put into extending the capabilities of the STB in order to enhance the digital television viewing experience.
- the digital television format has many advantages over analog television, and extends the capabilities of the analog television format, certain difficulties arise that are inherent within the digital format. As an example, switching between channels using analog methods is very fast; however, switching in digital television format is relatively slow. There are several reasons for this difference in switching speed in analog and digital television.
- the digital television signals comprise large data quantities and require a large amount of memory on the STB.
- MPEG Joint Photographic Experts Group
- MPEG compression Even with MPEG compression, however, delivery of the first picture of a selected digital television channel upon changing channels is a time-consuming process due to the delays associated with digital television.
- a significant portion of the delay in switching between channels in a digital television network is attributable to the acquisition of digital data, including decrypting and decoding information, and the processing of the data for the newly selected channel. Additional delay is incurred due to the nature of the MPEG signals.
- MPEG video is broken up into a hierarchy of layers to facilitate error handling, random searching, editing, and synchronization with other signals, for example, an audio bit stream.
- the first MPEG layer is known as the video sequence layer and comprises information such as frame size, bit rate, and frame rate.
- the second MPEG layer is the group of pictures layer, which comprises one or more groups of frames, some frames being intra-frames (I- frames) and others being predictive frames (P-frames) or bi-directional frames (B-frames).
- the third layer, the picture layer comprises the frame and frame size information.
- the video sequence of the group of pictures layer is built upon the most recently received I-frame and its subsequent P- and B-frames.
- the I-frame is the critical first frame of the video sequence. If a viewer changes channels sometime after the time at which an I-frame was transmitted, the viewer must wait until the next I-frame is transmitted and received to decode subsequently received Panel B- frames and P-frames.
- I-frames are transmitted at a limited frequency, such as typically twice a second or even less frequent. In many applications, the sequence is also protected from unauthorized viewing by scrambling the compressed bitstream during transmission. In order to descramble the I-frames (and, in most cases, B- frames and P-frames as well), it is also necessary to utilize control words used by the conditional access system.
- control words are extracted from Entitlement Control Messages (ECMs) during a decryption process and are used in descrambling the MPEG signal received from a given channel.
- ECMs Entitlement Control Messages
- the need for descrambling and decryption further adds to the channel switching delay time, as control words are also sent at low frequency and decryption is a time consuming operation.
- the digital reception and display of the digital television signal involves the use of one or more buffers within the STB in which the compressed signals are temporarily stored for short periods of time.
- the broadcast signal is pulled from the incoming transport stream and sent to a buffer stream.
- An MPEG decoder later pulls the stored broadcast signal from the stream buffer and, after decoding, sends the resultant signal to the video display.
- the decompressed video frames are further buffered to be available for subsequent decoding operations.
- the use of the buffer allows for many new possibilities, such as playing back a live broadcast while it is being recorded simultaneously.
- the buffer and decoder both cause delays as do waiting for decryption and control words necessary to decode and access a protected video sequence.
- a method and apparatus to reduce delay when changing channels in a television environment is described.
- Figure 1 is a diagram of the path that a signal traverses from a broadcast stream to a video display
- Figure 2 is a diagram representing a sequential arrangement of MPEG compressed video frames in a portion of an MPEG video sequence
- Figure 3 is a diagram representing an example buffer load and flush scheme utilized in a set-top box
- Figures 4-6 show apparatus, in accordance with example embodiments, that buffers I-frames to reduce delay between selecting a channel and displaying the selected channel in a television environment;
- Figures 7-8 show apparatus, in accordance with example embodiments, that buffers control words to reduce delay between selecting a channel and displaying the selected channel in an television environment;
- Figure 9 shows a conditional access card in accordance with an example embodiment
- Figure 10 shows a method, in accordance with an example embodiment, for reducing delay between selecting a channel and displaying the selected channel in a television environment
- Figure 11 shows a diagrammatic representation of machine in the example form of a computer system within which a set of instructions, for causing the machine to perform any one or more of the methodologies discussed herein, may be executed.
- An embodiment addresses the problems of time delays between the moment of choosing a digital television channel and the moment at which the first image from the selected digital television channel appears on the screen (e.g., television screen) in a digital television environment.
- this delay may be due to several cumulative delay factors, for example, buffer access delay, MPEG sequencing delay, decrypting delay, and decoding delay.
- buffer access delay for example, MPEG sequencing delay
- decrypting delay for example, MPEG sequencing delay
- decoding delay decoding delay
- the methodologies described herein are not restricted to broadcasting but apply equally to unicasting.
- the term "television channel" is intended to include any video or moving picture that is communicated to users via any network and is intended to include communications via the Internet.
- a larger storage capacity in a Set-Top Box (STB) and client device allows for more signals to be retained in the buffer by the client/STB.
- These extra signals may comprise signals from TV channels other than a channel currently being viewed.
- Existing STBs which typically only have one tuner and one MPEG decoder, can acquire multiple channels and transfer them into a single buffer as long as these channels are located in the same frequency. For example, the most popular six channels may be multiplexed together (e.g., CNN, ESPN, WB,
- An embodiment of the present invention takes advantage of STBs (optionally with mass storage) which have multiple front-end tuners and therefore are able to acquire multiple programs simultaneously. Multiple digital channels maybe multiplexed on a single frequency. Moreover, new MPEG chipsets may decode multiple streams at the same time. Likewise, faster smart cards (or equivalent security devices such a non-removable secure device glued on the motherboard) or a remote authentication server, could speed up acquisition of control words. An example embodiment may utilize all of these new capabilities to reduce the delay in channel switch times on digital television or information networks (satellite or cable).
- An example embodiment provides storage for a received MPEG signal for a non-viewed channel in a circular buffer.
- the buffer is updated (e.g., flushed) periodically so that only the most recent portion of each digital television signal is retained and stored in the buffer at all times.
- the buffered channel signal can be viewed without having to wait through a buffer delay or an MPEG sequencing delay.
- the most recently transmitted entry point typically an I-frame
- the stored signal for the new channel is accessed from the entry point that has been captured in the buffer.
- VBV Video Buffer Verifier
- channels that are broadcast at frequencies other than the frequency of the channel currently being viewed are stored.
- the decoders that are not only used to decode the viewed channel but are also used to decode the signals from other channels not being viewed, thereby removing decoding delays from the channel switching time.
- the decoded signal is ready for display upon changing channels.
- only a single decoder may be present that can decode faster than real-time and the decoder may time slice between multiple decode sessions.
- the decoder may time slice between a decode session A on channel A and a decode session B on channel B (e.g., decompress one frame of channel A, then one frame of channel B, etc.). In these circumstances, the decoder may buffer the decompressed output of channel B, but only display the decompressed output for the current channel (e.g., channel A). When the user switches to channel B, the decoded frames are presented immediately.
- an embodiment includes a set of rules, which are provided for determining which channel information to store in the circular buffer. These rules may be based, inter alia, on frequency of channel use, currently viewed channels, and adjacency to the channel currently being viewed.
- Figure 1 shows a diagram of an example path that a signal takes from the broadcast stream to the user's video display.
- an MPEG stream provided by a content provider, is broadcast by a head-end and received by a tuner 101, and is then sent to a demodulator 103 coupled to a client device.
- the demodulator 103 stores the signal into a circular buffer 105 for later access processing and display.
- an output of the demodulator 103 may go through a demultiplexer that may reject some of the packets of the MPEG stream (e.g., the demultiplexer may only keep packets relevant to the channels that are to be buffered).
- the decoder 107 reads in a coded bit stream and may output decoded pictures, audio samples, or data objects to a digital buffer 109.
- Figure 2 shows a portion of an MPEG video frame sequence.
- Frames are broadcast by the head-end, received by the client, and read sequentially from left to right as shown in Figure 2.
- I-frames 200, 210 are frames whose coding is based upon spatial redundancies within the frame.
- Other frame types such as P-frames 202 and B-frames 204, use the I-frame as a basis for temporal predictions and coding.
- P-frames comprise elements predicted and based on the previous I-frame or P-frame.
- B-frames comprise predicted elements from an immediately subsequent frame as well as from an immediately previous frame. Frames that predict the content of B-frames may be either P- or I- frames.
- B-frames are not used in prediction of any other frame type. It will however be appreciated that the invention also applies to other standards (e.g., MPEG-4, Windows Media, H.264, or the like).
- MPEG-4 Windows Media
- H.264 Windows Media
- a viewer switches to the channel at the point when, for example, the B-frame 206 is currently being received.
- the viewer can not view this frame, as the basis I-frame 200 has not been captured by the tuner. Instead, the viewer must wait until the next I-frame 210 is received before being able to decode and view an image from the newly selected channel, this first image being the image of I-frame 210.
- the frequency at which I- frames arrive is about twice per second or slower on average, so the total possible delay from waiting on an I-frame can be up to approximately 500 milliseconds and more.
- An average delay time for arrival of an I-frame, due to MPEG sequencing, may be approximately 250 milliseconds.
- Another typical switching delay is associated with the operation of the circular buffer 105 (which may include the VBV buffer).
- Figure 3 shows a graph of buffer load 302 (see buffer 105) versus time 304.
- the circular data buffer 105 fills until it reaches a desired buffer level 310, at which time, it discharges. A first discharge is shown in Figure 3 at the time 1 (see arrow 308).
- Frames are shown by way of example to be added incrementally to the buffer at times 2 (see arrow 312), 3 (see arrow 314), 4 (see arrow 316), and 5 (see arrow 318).
- a newly acquired frame causes the bit load to exceed the desired buffer level, and the buffer is once again discharged into the decoder 107. In this manner, only the most recent frames are stored in the buffer 105.
- the wait time for the filling of the buffer is B/R, where B is the desired buffer level, and R is the rate of the bit stream.
- the average time for the buffer to fill may, for example, be approximately 400 msec.
- the buffer flushes all data received prior to each I-frame. Each I- frame may then be placed at the start of the buffer 105 and subsequently received data written in after the I-frame.
- Descrambling and decoding of the MPEG stream may cause further delays.
- the MPEG stream is secured by interaction with control words (obtained during decryption of the ECMs received in the stream) of the conditional access system, adding further delay.
- Decoding may take place in real time or better. As a consequence, the decoding speed may not be less than 30 frames per second for NTSC and 25 for PAL. The accumulation of all these delays leads to an overall delay of at least 3/4 of a second and upwards, and often from 1.5 seconds to 3 seconds.
- NIT Network Information Table.
- SDT Service Description Table.
- PSI Program Specific Information.
- PAT Program Association Table.
- PMT Program Map Table.
- CA Conditional Access.
- ECM Entitlement Control Message.
- At least reducing the delay associated with the control word and I- frame can reduce the delay significantly.
- decryption keys such as control words are stored for immediate access for decryption and access upon selection of a channel, or for decryption and access in real time when using multiple buffers, and/or multiple decoders.
- An example embodiment may reduce (and, for example, substantially eliminate) channel switching delays by storing, decoding and accessing MPEG streams from channels other than the channel currently being viewed. Once a viewer selects a channel, in an example embodiment, the STB (receiver) no longer needs to retrieve the stream immediately from the broadcast stream, but rather the STB retrieves the stored signal initially from the buffer without having to wait on arrival of additional data, for example, I- frames or control words.
- An example embodiment pre-processes the buffer 105 to ensure that the latest I- frame is at the beginning of the buffer 105 or at least at a pointer location pointing to a location in the buffer 105.
- a STB 400 may comprise two or more tuners 401.1-401.1, two or more demodulators 403.1 -403.m, and two or more circular buffers 405.1 -405. n.
- a second tuner 401.2 gives the viewer the advantage of receiving channels that are transmitted at separate frequencies.
- a first tuner 401.1 may be tuned to the channel currently being viewed.
- the second tuner 401.2 simultaneously receives a signal from a separate channel not being viewed.
- the second tuner 402.2 sends its data to a second demodulator 403.2 and then into a second circular buffer 405.2.
- a channels selector 410 may select channels in response to a viewer selection.
- An example embodiment enables switching to the new channel to appear to be immediate; however, the image displayed on the display device (e.g., TV, computer screen or the like) may lag behind the actual broadcast. This lag is due to the need to access the most recent I-frame of a stored sequence rather than the most recent frame of the broadcast sequence. Thus, the time between the last stored I- frame and the current broadcast frame represents a lag time between the displayed frame from the stored signal and the current broadcast frame. The amount of this lag depends on the position of the entry point in the buffer at the time channel selection occurs. The ability of the example embodiments to reduce channel switching delays increases with the size of the buffer 105.
- a STB or receiver 500 further comprises multiple decoders 507.1 -507.p, thereby allowing multiple incoming streams to be decoded before being sent to a video display buffer.
- decoding takes place prior to channel selection further reducing delays and it is possible for the viewer to switch (see switch 510) completely to the most recent I-frame of the decoded signal, and thus to begin viewing immediately.
- additional decoders for the non-viewed channels may thus provide an advantage of reducing delay due to signal decoding.
- the channel selector 510 may be responsive to a remote control device (e.g., a handheld remote control operable by a viewer), a computer keyboard, or the like.
- channel switching may be done automatically, without input from the viewer.
- the receiver could switch seamlessly from a live channel to a targeted commercial transmitted on another channel, and then return seamlessly to the main live program at the end of the commercial.
- a targeted commercial could be inserted in the following manner: a viewer may watch channel A and, during a commercial break, channel A may transmit 4 different commercials on 4 other channels (A, Al, A2, A3) each of which may be targeted at 4 different profiles.
- the receiver may detect a trigger indicating an advertisement break (for example, the trigger can be transmitted in-band, multiplexed with the Audio/Video). The receiver may then buffer and tune to the appropriate channel depending on the profile of the viewer.
- transmission of the trigger and of the advertisements/commercials may be scheduled shortly before the commercial break to make sure that sufficient data is stored in the buffer at the time the receiver switches channels.
- the methodology described in this document is not restricted to switching between channels received by tuner 1 401.1 and tuner 2 401.2 and can apply to switching between any two channels. Accordingly, the methodology can also apply when switching between any two buffered channels.
- example embodiments are described with reference to I-frames defining an entry point required for processing a television signal for display to a viewer, other entry points my be defined in different deployments or compression methods.
- the storage may be updated to maintain a most recently received entry point of the stored channel.
- an example embodiment also determines which channel signals to store in the storage or circular buffer.
- a plurality of tuners 601.1-601.1 are connected to a plurality of demodulators 603.1- 603.m.
- a buffer input selector 612 determines which channel is to be fed into a particular buffer (e.g., buffer 605). It will be appreciated that more than one buffer may be present.
- channels adjacent to the currently viewed channel are stored, where an adjacent channel can refer to channels whose channel numbers are adjacent to the current channel in a given mode (e.g., in a favorite channels mode, an all channels mode, or other mode or configuration).
- Another example channel selection rule or mode may comprise a list of only those favorite channels of the viewer based on the viewing habits and history for the viewer.
- Another example selection rule or mode may select and store the signals of channels that are watched with higher frequency (more regularly), where the frequency can be determined either on a long-term general basis or on a more recent basis.
- those channels that have been viewed last are stored.
- an option may be provided to store the next channel up or down when the user has pushed the up or down button last.
- the advantage of these example strategies is that those channels that are most likely to be next chosen by the viewer will have the least amount of display delay upon selection.
- Figure 7 shows apparatus 700, in accordance with an example embodiment, that buffers control words to reduce delay between selecting a channel and displaying the selected channel in a television environment.
- a demodulator 703 may demodulate multiple television channels received on a single frequency from a content provider (e.g., a transponder of a content provider). Thereafter, an a content provider (e.g., a transponder of a content provider). Thereafter, an a content provider (e.g., a transponder of a content provider).
- a content provider e.g., a transponder of a content provider
- Entitlement Control Message (ECM) filter may extract an ECM associated with each decoded channel and communicate the ECMs to a control word manager 708 (see lines 707 which show three example ECMs).
- ECM Entitlement Control Message
- the apparatus 700 stores or buffers control words of channels not currently selected based on selection rules.
- control word manager 708 may receive ECMs from multiple channels and select which control words it will buffer based on selection rules or criteria provided in a selection rules module 710.
- the selection rules may be similar to the input selection rules 614 that may determine which of the channels should have their I-frames stored. Different selection rules or criteria may be applied to decide which channels to process at any point in time.
- the STB could process the most frequently watched channels, a list of favorite channels specified by the viewer, a list of the most important channels specified by an operator, adjacent channels to the one the viewer is currently watching (e.g. monitor the current channel, as well as the 5 previous channels and the 5 next channels in the order tied to program keys on a remote control), or a combination of criteria.
- the number of channels to process may be dynamic.
- the STB or receiver could send the next control word in the list (e.g., going down in an order of priority in a list of channels) until decryption of a higher priority control word is required.
- the priority list may be updated dynamically (e.g. when the user changes channel). Since the ECMs change periodically, in an embodiment the list will also change periodically. For example, a new ECM may appear on a high priority channel, in which case the new ECM will be inserted at the top of the list. On the other hand, some ECMs will expire and be removed from the list.
- conditional access card 712 e.g., a smart card associated with the STB
- conditional access device e.g., a secure non-removable device or an authorization/authentication server.
- the conditional access card 712 may then extract the control words from the ECMs that it receives and communicate them (see lines 714) to a payload descrambling module 716.
- the control word for a newly selected channel is already available as the conditional access card 712 has already performed this functionality. Accordingly, the delay in changing channels may be reduced.
- the CWs once extracted by the smart card, may be transmitted to the receiver in an encrypted form (e.g., using a receiver specific key). Accordingly, sharing control words and ultimately descrambling movies without authorization may be inhibited. Re-encrypted control words may then be sent to the decoder, which is a secure device that knows the receiver specific secret required to decrypt the re-encrypted CWs.
- the CW buffer could buffer re-encrypted CWs.
- the ECMs may be communicated via a television signal that is broadcast (e.g., via a satellite signal).
- the ECMs may be communicated via a route that is independent of the content being communicated (e.g., the ECMs may be communicated via the Internet or stored in the STB a head of time).
- the channel information (including ECMs) and the video or television content are communicated via the Internet.
- the embodiments described herein are not limited to smart cards and relate to any secure device such as non-removable circuitry, an authorization or authentication server or the like.
- the selection rules 710 and the control manager 708 are shown, by way of example to be part of the STB. However in an embodiment, the selection rules and the control manager are included within the conditional access card 712 as shown by module 718.
- the input selection rules 614 may be integrated within the conditional access card (e.g., a smart card).
- Figure 9 shows an example conditional access card 900 in which a control word manager 908 and selection rules 914 are integrated within the card 900.
- the ECMs and control words may be communicated serially or in parallel between the conditional access card and the STB.
- control words are not decrypted as they are needed at the time a user decides to change to a new channel, but as soon as possible, so that the control word has been decrypted by the time it is required to change channels.
- control words for a given channel typically change every 5 Seconds or so and may be sent 5 seconds ahead of time.
- smart cards may need less than 0.5 second to decrypt a control word.
- a smart card in accordance with an example embodiment of the invention may process control words for as many as 10 channels at the same time, as long as the requests to decrypt control words can be processed in sequence.
- STB (or any digital receiver) may collect encrypted control words for multiple channels at any time. The receiver may send requests to decrypt control words sequentially to the conditional access card, or the conditional access card may queue requests internally.
- FIG. 8 shows apparatus 800, in accordance with an example embodiment, that buffers control words to reduce delay between selecting a channel and displaying the selected channel in a television environment.
- the apparatus 800 includes multiple tuners 801.1-801.1 connected to multiple demodulators 803.1-803.m.
- ECM filters 818.1-801.r extract ECMs from the received signal and communicates them to a control word manager 808.
- the control word manager 808 may identify or select one or more ECMs for one or more channels not currently being viewed based on selection rules provided by a selection rules module 810.
- each demodulator 818.1-818.r may demodulate multiple channels carried on a single frequency.
- entire streams may be cached in the STB to further accelerate channel change. For example, if I-frames were spaced every 2 seconds, the apparatus could cache 2 seconds of MPEG program stream for another channel not currently being watched. Different criteria could be applied to decide which channels to cache as described above. Thus, for receivers with sufficient memory (even with one tuner), multiple or all channels transmitted on a particular frequency can be cached.
- An example strategy to decide which channel(s) to cache could be:
- Figure 10 shows a method 1000, in accordance with an example embodiment, to reduce delay when changing channels in a television environment.
- a plurality of television channels may be received from a remote content provider, for example, via a satellite distribution network, cable distribution network, or the like.
- Each channel may include channel information required to display the channel.
- one or more of the received channels may be identified (see block 1004) as a buffered channel and channel information of the buffered channel(s) is stored in storage or memory (e.g., in a circular buffer), as shown in block 1006.
- the channel information includes at least one of a MPEG video I-frame and an access control word. Accordingly, when changing channels it may not be necessary to wait for the next I- frame and ECM to display a newly selected channel.
- the storage may be updated to maintain a most recently received I-frame,
- the buffered channel may be a second channel signal broadcast over a separate frequency, and that the I-frame for the buffered channel may be placed at a beginning of the storage.
- the stored channel signal may be demodulated and, optionally, decoded prior to selection of the stored channel for display. Control of multiple channels other than a currently viewed channel may be stored or buffered. In an embodiment, display delay may be reduced by lagging the displayed image behind an actual broadcast or accelerating playback of the stored channel to synchronize playback with a live broadcast.
- At least one channel of the plurality of channels may be identified as a buffered channel and the identification may be based upon channel input selection rules.
- the selection rules may comprise selecting at least one of an adjacent channel, a favorite channel, and a channel frequently watched.
- the STB may monitor use behavior, and in response to monitored behavior buffer channels that a user is more likely to view.
- the present invention has been described by way of example in a television environment. However, the present invention may also be embodied in a distributed computer system comprising a server and a client device.
- the client device may be a hand-held computer, cell phone, personal digital assistant or any device capable of receiving and/or transmitting an electronic signal.
- the present invention is implemented as a set of instructions on a computer readable medium, comprising ROM, RAM, CD ROM, Flash or any other computer readable, medium, now known or unknown that when executed cause a computer to implement the method of the present invention.
- the decoder 107 performs access control functionality and thus descrambles incoming television signals.
- a scrambler module at, for example, a head-end may include a control word (CW) generator.
- Control words are required by a STB for decrypting television signals.
- the control word generator may produces random numbers to scramble the transmitted television signal.
- An entitlement control message (ECM) generator may encrypt the control word (and other relevant data) for broadcasting as an ECM.
- An ECM is an access packet that contains information the conditional access card (e.g., a smart card in a STB) needs to determine the control word that decrypts the video content it receives.
- a control word may be changed at regular intervals and a new ECM including the control word is then transmitted or broadcast.
- a descrambling process is performed by a decoder of the STB and, in order to accomplish this, the control words are required.
- extraction of the control word from the ECM may also result in delays when changing channels as the STB needs a new CW for the channel that has been selected for viewing by the user.
- the ECM message may be inserted in a broadcast stream and be received by all STBs listening to a broadcast stream. Only those STBs who have the requisite rights will be able to decrypt the ECM and retrieve the CW required for descrambling.
- the ECMs may be received separately from the audio/video.
- a method, apparatus and device which buffer ECMs and CWs. While this mechanism can be used to accelerate channel change, it can also be used in other cases where multiple channels need to be processed at the same time.
- An example is the case where a Personal Video Recorder (PVR) needs to record one channel while the user watches other channel(s).
- the PVR may descramble the channel before optionally re-encrypting it using another method (e.g. triple DES or AES). It can also be that the user is watching two channels at the same time (Picture-In-Picture). It can also be that the receiver is processing multiple channels at the same time, to display one channel on a first TV and another channel on another TV.
- PVR Personal Video Recorder
- the number of channels that can be processed by the smart card may be increased, since ECMs do not need to be processed real-time.
- the number of channels that can be subsequently be descrambled or decoded or displayed simultaneously will then become a function of the capabilities of the receiver for descrambling, decoding or display.
- a receiver needs to display a user defined mosaic (multiple channels, e.g., based on user preference or network sorting that may appear on the screen in thumbnail size).
- Each channel may be transmitted full screen, in which case the receiver would need to decode and resize the channels, or the network operator may decide to transmit a thumbnail size version of each channel in addition to the full-screen version.
- the receiver may have to display a combination of channels transmitted separately, and it is possible that each channel will be scrambled separately (since different rights may be associated with different channels).
- the number of channels the smart card can process can be increased, in order to increase the number of channels that can be presented in the mosaic.
- the number of channels that can be subsequently be descrambled or decoded or displayed simultaneously will then become a function of the capabilities of the receiver for descrambling, decoding or display.
- prior art conditional access cards can result in delays in obtaining control words and thereby prevent, for example, displaying multiple thumbnails where each thumbnail required decoding. Further, prior art conditional access cards process ECMs to extract the control words in real-time and it will be appreciated that this may severely limit the number of channels or thumbnails than can be decoded and displayed by a STB or receiver. In order to enhance the number of channels that may be decoded, in an example embodiment, the controls words are decrypted (extracted from the ECMs) in a sequence and buffered in the STB or receiver (or conditional access card) for sequential processing.
- the decryption of the control words may be time shifted to enhance the throughput of control words to the decoder as long as the audio and the video is buffered and the time shifting in the audio and the video corresponds to the time shifting in the control words.
- all control words are not provided in real-time.
- the video stream or television channel is also buffered (e.g., buffered for 5 seconds) and the ECMs are communicated to the conditional access device which then decrypts them in a time-shifted manner.
- the decrypted control words are then communicated to the decoder to decode the buffered video stream or television channel.
- control words for a given channel typically change every 5 seconds and are sent 5 seconds ahead of time.
- smart card requiring less than 0.5 seconds to decrypt a control word, as many as 10 channels may be processed at the same time when the requests to decrypt control words are processed in a time-shifted sequence.
- the method described herein extends to decrypting a plurality of incoming television channels or video streams.
- the method may include receiving the plurality of television channels and a plurality of encryption keys at the receiver. Thereafter, the encryption keys of more than one television channel are buffered. Each encryption key may be required for decryption of an associated television channel or video stream. A buffered encryption key may be selected from a plurality of buffered encryption keys and an incoming television channel associated with the buffered encryption key may then be decrypted.
- encryption keys are included within the television or video signal. Accordingly, the method may include extracting an encryption key from each television channel. In a different embodiment, the encryption keys are received independently of the television channel.
- the encryption keys may be control words and thus the method may include buffering Entitlement Control Messages and subsequently extracting the control words, or extracting the control words from the Entitlement Control Messages and then buffering the control words.
- the encryption keys (e.g., Entitlement Control Messages or control words) are buffered in a conditional access device (e.g., a smart card, a non-removable security device embedded in a received, or an authentication server).
- a conditional access device e.g., a smart card, a non-removable security device embedded in a received, or an authentication server.
- Figure 11 shows a diagrammatic representation of machine in the example form of a computer system 1100 within which a set of instructions, for causing the machine to perform any one or more of the methodologies discussed herein, may be executed. In alternative embodiments, the machine operates as a standalone device or may be connected (e.g., networked) to other machines.
- the machine may operate in the capacity of a server or a client machine in server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment.
- the machine may be a personal computer (PC), a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine.
- the example computer system 1100 includes a processor 1102 (e.g., a central processing unit (CPU), a graphics processing unit (GPU) and/or a digital signal processing unit (DSP)), a main memory 1104 and a static memory 1106, which communicate with each other via a bus 1108.
- the computer system 1100 may further include a video display unit 1110 (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)).
- the computer system 1100 also includes an alphanumeric input device 1112 (e.g., a keyboard), a user interface (UI) navigation device 1114 (e.g., a mouse), a disk drive unit 1116, a signal generation device 1118 (e.g., a speaker) and a network interface device 1120.
- an alphanumeric input device 1112 e.g., a keyboard
- UI user interface
- disk drive unit 1116 e.g., a disk drive unit
- signal generation device 1118 e.g., a speaker
- network interface device 1120 e.g., a network interface device 1120.
- the disk drive unit 1116 includes a machine-readable medium 1122 on which is stored one or more sets of instructions and data structures (e.g., software 1124) embodying or utilized by any one or more of the methodologies or functions described herein.
- the software 1124 may also reside, completely or at least partially, within the main memory 1104 and/or within the processor 1102 during execution thereof by the computer system 1100, the main memory 1104 and the processor 1102 also constituting machine-readable media.
- the software 1124 may further be transmitted or received over a network
- machine-readable medium 1122 is shown in an exemplary embodiment to be a single medium, the term “machine-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions.
- the term “machine-readable medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present invention, or that is capable of storing, encoding or carrying data structures utilized by or associated with such a set of instructions.
- machine-readable medium shall accordingly be taken to include, but not be limited to, solid-state memories, optical and magnetic media, and carrier wave signals.
- machine-readable medium shall accordingly be taken to include, but not be limited to, solid-state memories, optical and magnetic media, and carrier wave signals.
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- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
- Circuits Of Receivers In General (AREA)
Abstract
Description
Claims
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Also Published As
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US20060085828A1 (en) | 2006-04-20 |
WO2006044547A3 (en) | 2006-11-30 |
JP2008517536A (en) | 2008-05-22 |
EP1800479A4 (en) | 2010-07-21 |
BRPI0516492A (en) | 2008-09-09 |
EP1800479A2 (en) | 2007-06-27 |
CN101077003A (en) | 2007-11-21 |
AU2005295772A1 (en) | 2006-04-27 |
EP3468175A1 (en) | 2019-04-10 |
AU2005295772B2 (en) | 2009-10-29 |
JP2011139501A (en) | 2011-07-14 |
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