US 20060253868 A1
A method and apparatus for combining video frame sequences with a video display of an interactive program guide (IPG). The apparatus comprises a plurality of compositors that combine background information, video frame sequences and program guide graphics into a single video frame sequence. The sequence is then digitally encoded to form an MPEG-like bitstream. The same background information and informational video is composited with a different program guide graphic to form another video sequence that is also encoded. A plurality of such sequences are produced with each sequence having a different program guide graphic. Each sequence is encoded and then multiplexed into a transport stream such that all the encoded sequences are transmitted to a subscriber's terminal using a single transport stream. As such, the subscriber can transition from one program guide to the next without interruption of the background or video display as the program guide graphic is changed.
1. A method of encoding a plurality of program guide pages, comprising:
encoding each program guide page to form a plurality of program guide page representative bitstreams;
determining a longest bitstream;
associating null packets with at least some of the bitstreams to provide a plurality of bitstreams having substantially similar lengths; and
associating at least one switching packet with the end of each bitstream.
2. The method of
3. The method of
retrieving the bitstreams from the buffer; and
adapting the retrieved bitstreams to form respective transport streams having substantially similar lengths.
4. The method of
5. The method of
6. The method of
7. The method of
8. The method of
9. The method of
10. The method of
11. The method of
12. The method of
13. A method of encoding a plurality of program guide pages comprising the steps of:
encoding each program guide page to form a respective bitstream;
buffering the bitstreams for all the guide pages;
retrieving said bitstreams from a buffer;
ordering the bitstreams into a transport stream to equate the length of the transport stream with the length of other transport streams; and
adding switching packets to the transport stream.
14. A method of encoding a plurality of program guide pages comprising the steps of:
contemporaneously encoding each program guide page to form respective bitstreams;
assembling a transport stream containing each bitstream in successive order;
adding switching packets into the transport stream after the bitstreams.
This application is a continuation of commonly assigned pending U.S. patent application Ser. No. 09/359,561 filed Jul. 22, 1999 which application claims benefit of U.S. provisional patent application Ser. No. 60/093,891 filed Jul. 23, 1998 which is hereby incorporated herein by reference. U.S. patent application Ser. No. 09/359,561 is also a continuation-in-part of commonly assigned U.S. patent application Ser. No. 09/293,526 filed Apr. 15, 1999 and commonly assigned U.S. patent application Ser. No. 09/201,528 filed Nov. 30, 1998. All of the prior applications are hereby incorporated herein by reference.
1. Field of the Invention
The invention relates to electronic program guides and, more particularly, the invention relates to a technique for encoding a user interface of an information distribution system.
2. Description of the Background Art
In several communications systems, the data to be transmitted is compressed so that the available transmission bandwidth is used more efficiently. For example, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1 refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is also incorporated herein by reference. A compressed digital video system is described in the Advanced Television Systems Committee (ATSC) digital television standard document A/53, and is incorporated herein by reference.
The above-referenced standards describe data processing and manipulation techniques that are well suited to the compression and delivery of video, audio and other information using fixed or variable rate digital communications systems. In particular, the above-referenced standards, and other “MPEG-like” standards and techniques, compress, illustratively, video information using intra-frame coding techniques (such as run-length coding, Huffman coding and the like) and inter-frame coding techniques (such as forward and backward predictive coding, motion compensation and the like). Specifically, in the case of video processing systems, MPEG and MPEG-like video processing systems are characterized by prediction-based compression encoding of video frames with or without intra- and/or inter-frame motion compensation encoding.
Over the past few years, television has seen a transformation in a variety of means by which its programming is distributed to consumers. Cable television systems are doubling or even tripling system bandwidth with the migration to hybrid fiber coax (HFC) cable plant thereby offering a larger number of channels to the viewer. Customers unsatisfied with their local cable systems have switched in high numbers to direct broadcast satellite (DBS) systems. And, a variety of other approaches have been attempted focusing primarily on high bandwidth digital technologies, intelligent two way set top boxes, or other methods of trying to offer service differentiated from standard cable and over the air broadcast systems.
With this increase in bandwidth, the number of programming choices has also increased. Leveraging off the availability of more intelligent set top boxes, several companies such as Starsight and Prevue Guide have developed elaborate systems for providing an interactive listing of a vast array of channel offerings, expanded textual information about individual programs, the ability to look forward to plan television viewing as much as several weeks in advance, and the option of automatically programming a VCR to record a future broadcast of a television program.
Unfortunately, the existing program guides have several drawbacks. They tend to require a lot of memory, some of them needing upwards of one megabyte of set top terminal (STT) memory. They are very slow to acquire their current database when they are activated for the first time or are subsequently restarted (e.g., a large database may be downloaded to a STT using only a vertical blanking interval (VBI) data insertion technique). Disadvantageously, such slow database acquisition may result in out of date database information or, in the case of a pay per view (PPV) or video-on-demand (VOD) system, limited scheduling flexibility for the information provider. The user interface to existing program guides does not usually look like a typical television control interface; rather looks like a 1980's style computer display (i.e., blocky, ill-formed text and/or graphics).
Additionally, the present program guides may provide an advertising or preview region along with the program guide graphics. However, the insertion of these additional video signals is performed using an analog compositor that merely inserts (overlays) the additional imagery into the broadcast stream. The analog compositing process is accomplished and then the new analog video containing an advertisement or preview and the program guide are recorded on tape for subsequent broadcast. This compositing process is not accomplished in real time at the head end of the cable system and, consequently, the program guide can not contain targeted advertising for a particular household or a particular neighborhood or region. The program guide with its associated preview or advertising is broadcast to all subscribers connected to the head end of the cable system. Additionally, these program guides are generally passive, in that, the viewer sees the program guide information change on the screen to indicate different programs and their associated channels. However, there is no provision enabling a viewer to interact with the program guide display to scroll through the channel or channels that are available. Because such scrolling in an analog system requires a splice to a new program guide video sequence, the program guides that are interactive do not include advertising video or other video information with the program guide.
Therefore, it is desirable to provide a method and apparatus for encoding an interactive program guide.
The disadvantages associated with the prior art are overcome by the present invention of a method and apparatus for encoding user interface of an information distribution system. One embodiment of such user interface is an interactive program guide (IPG) that forms an IPG screen or page containing a graphical guide region and a video region playing at least one video sequence. The invention is a method and apparatus for performing ensemble encoding of one or more IPG pages. The invention comprises a plurality of compositors that combine background information, informational video and program guide graphics into a single sequence of video frames. The sequence is then digitally encoded to form an MPEG-like bitstream. The same background information and informational video is composited with a different program guide graphic to form another video sequence that is also encoded. A plurality of such bitstreams are produced with each sequence containing a different program guide graphic. The encoding is performed using a common coding profile and a common clock for each of the encoders. The encoded sequences are then multiplexed into at least one transport stream such that all the encoded sequences are transmitted to subscriber equipment using one or more transport streams. As such, the subscriber can transition from one program guide page to the next without interruption of the background or informational video as the program guide page graphic is changed.
The informational video may appear in multiple locations upon the IPG screen. Promotional or advertising video may appear in one portion while an animated graphic appears in another location. Each of the informational video streams may have a different rate of display. The encoders handle different video rates by using slice based encoding of the composite image sequence.
One example of a program guide that is encoded in accordance with the invention has each graphic containing a set of programs (e.g., channels) listed along a left, vertical axis and each program associated with the channel is identified in a rectangular cell that extends toward the right. The horizontal axis represents time and about 1.5 hour of programming for ten channels is shown in each program guide graphic page. The informational video is generally contained in one or more regions above the program graphic.
In another example of a program guide that is encoded in accordance with the invention has each graphic containing a set of programs (e.g., channels) listed along a left, vertical axis and each program associated with the channel is identified in a cell that is listed beneath a time axis. The horizontal axis represents time and about 1.5 hours of programming for eight channels is shown in each program guide graphic page. Each channel is associated with text that represents three programming slots, one for each half hour in the time axis. The informational video is generally contained in one or more regions next to the program graphic, i.e., a guide region is on the left half of the screen and the video region is on the right half of the screen or vice versa.
The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
In general, the SPE 102 produces a plurality of digital bitstreams that contain encoded information (e.g., television programming in an MPEG-like compressed form). These bitstreams are modulated using a modulation format that is compatible with the distribution network 104. The subscriber equipment 106, at each subscriber location 106 1, 106 2, . . . , 106 n, comprises a demodulator/decoder 124 and a display 126. Upon receiving a bitstream, the subscriber equipment decoder 124 extracts the information from the received signal and decodes the stream to produce the information on the display, i.e., produce a television program or program guide page.
In an interactive information distribution system such as the one described in commonly assigned U.S. Pat. No. 6,253,375, issued Jun. 26, 2001, the program bitstreams are addressed to particular subscriber equipment locations that requested the information through an interactive menu. An appropriate interactive menu structure for requesting video on demand is disclosed in commonly assigned U.S. Pat. No. 6,208,335, issued Mar. 27, 2001.
To assist a subscriber (or other viewer) in selecting programming, the SPE 102 produces a interactive program guide (IPG) in accordance with the present invention. The IPG of the present invention contains program information, e.g., title, time, channel, program duration and the like, as well at least one region displaying full motion video, i.e., a television advertisement or promotion. Such informational video is provided in various locations within the program guide screen.
As the video is recalled from device 108, each video sequence is coupled to the IPG generator 116. As such, three video streams and one audio stream (e.g., an audio stream associated with one of the advertisements) are provided to the IPG generator 116. Additionally, a background image is recalled from the storage device 118 under instructions from the controller 114. The background image is generally a static graphic, but it may be a video frame sequence containing moving imagery. Lastly, the IPG grid generator 120 provides a program guide graphic to the IPG generator 116. The IPG data for the graphic can be provided from any one of a number of sources such as a network cable feed, an internet site, a satellite feed, and the like. The guide program data is formatted, for example, into the rectangular grid graphic of program cells (screen 500 of
The IPG generator 116 performs ensemble encoding by combining the three video sequences, the background and the guide graphics into a comprehensive IPG display such as the one depicted as IPG page 500 in
The subscriber equipment 106 contains a demodulator/decoder 124 and a display 126 (e.g., a television). The demodulator/decoder 124 demodulates the signals carried by the distribution network 104 and decodes the demodulated signals to extract the IPG pages from the bitstream. As shall be described below, each of the IPG pages is identified with a unique program identification code (known as a PID) that is used by the demodulator/decoder 124 to select a bitstream for decoding. The decoded IPG page is displayed, as shown in
The composite image (e.g., three, full motion video frame sequences positioned upon a background image, the background/informational video) is coupled to a plurality of IPG grid compositors 202 1, 202 2, 202 3, . . . , 202 15 (collectively referred to as compositors 202). The compositors 202 combine the respective IPG graphics with the background/informational video combination to produce a plurality of video frame sequences containing a composite of the background, the informational video, and the IPG graphics. There is one frame sequence for each IPG graphic, e.g., fifteen sequences in all. As discussed previously, the IPG graphic is produced by the IPG grid generator 120. The IPG grid generator 120 actually produces two items, one is the IPG grid background image (the IPG grid graphic discussed above and shown as graphic 510 in
Each of the frame sequences (IPG screen sequences V1, V2, V3, V15) are coupled from the compositors 202 to the plurality of video encoders, e.g., real time MPEG-2 encoders 204 1, 204 2, 204 3, . . . 204 n (collectively encoders 204). Each encoder 204 encodes an IPG screen sequence to form a compressed video bitstream, e.g., an MPEG-2 compliant bitstream. The encoders use a common encoding profile and common clock supplied by the encoding profile and clock generator 250. As such, each sequence of IPG frames are synchronously encoded in the same manner.
The IPG grid foreground overlay graphics data is also coupled to the multiplexer 206 from the IPG grid generator 120. This graphics data is generally sent as “user data” or “private data” within the transport stream. Further discussion of the graphics data is provided below.
If the informational video in each IPG page have differing amounts of motion, the encoders can encode the video in a slice-based manner. As such, each frame is divided into a plurality of horizontal stripes of macroblocks. Each frame contains stripe start and stop identifiers. The information (pixels and/or macroblocks) between the start and stop identifiers can be encoded in a different manner than other portions of a given stripe. Consequently, a two dimensional region comprising portions of adjacent stripes can be encoded differently from other portions of the frame. The encoded information from the two dimensional region forms a bitstream that is identified by its own program identifier. At the subscriber equipment, the demodulator/decoder decodes the information in each slice, then reassembles the frame by placing the decoded slices into appropriate locations as identified by the slice start/stop identifiers. The two dimensional regions can be specified to align with the informational video such that the regions can contain video having different motion, i.e., fast versus slow motion. Consequently, one region could contain a slow moving animated character while another region could contain a fast moving sporting event promotion and both regions would be coded and decoded accurately.
All the compressed video streams (E1, E2, E3, . . . , E15) containing program guide information are multiplexed into a transport stream using multiplexer 206. These compressed video streams may contain the stripe-based encoded streams as well. In addition to the video information, audio information associated with one of the informational videos is also encoded and supplied to the multiplexer 206. The audio signal is delayed in audio delay 208, then encoded in the audio encoder 210. The delay compensates for the time required to perform video encoding of the associated video vis-a-vis the audio encoding. The compressed audio data is coupled to the multiplexer 206 for incorporation into the transport stream.
A transport stream, as defined in ISO standard 13818-1 (commonly known as the MPEG-2 Systems specification), is a sequence of equal sized packets, each 188 bytes in length. Each packet has a 4-byte header and 184 bytes of data. The header contains a number of fields, including packet identification number (PID). The PID field contains 13 bits and uniquely identifies each packet that contains a portion of a “stream” of video information as well as audio information and data. As such, to decode a particular video bitstream (or audio bitstream or data) for viewing, the decoder in the subscriber equipment extracts packets containing a particular PID and decodes those packets to create the video (and audio) for viewing.
Each of the fifteen bitstreams representing the IPG page sequences within a particular transport stream are uniquely identified by a PID. In the preferred embodiment, fifteen PIDs are multiplexed into a single transport stream. Certainly, less of more IPG bitstreams can be included in a transport stream as bandwidth permits. Additionally, more than one transport stream can be used to transmit the IPG bitstreams. For example, additional IPG pages may be encoded that represent additional time within a day or additional channels. The bitstreams representing the additional IPG pages are transmitted in additional transport streams. As such, many IPG pages representing 24 hours of programming on hundreds of channels can be broadcast to the subscriber equipment for selective display to a viewer.
An exemplary transport stream consists of N programs multiplexed together into one transport stream. Each program has its own video PID, which contains all the MPEG bits for a single guide page. All the programs share the same audio and PCR.
To change pages in the guide, it is required to switch between programs (video PIDs) in a seamless manner. This cannot be done cleanly using a standard channel change by the STT switching from PID to PID directly, because such an operation flushes the video and audio buffers and typically gives half a second blank screen.
To have seamless decoder switching, a splice countdown (or random access indicator) method is employed at the end of each video sequence to indicate the point at which the video should be switched from one PID to another.
Using the same profile and constant bit rate coding for each encoding unit, the generated streams for different IPG pages are formed in a similar length compared to each other. This is due to the fact that the source material is almost identical differing only in the characters in the guide from one page to another. In this way, while streams are generated in close lengths, they are not exactly the same lengths. For example, for any given sequence of 15 video frames, the number of transport packets in the sequence varies from one guide page to another. Thus a finer adjustment is required to synchronize the beginnings and ends of each sequence across all guide pages in order for the countdown switching to work.
The invention provides the act of synchronization of a plurality of streams that provides seamless switching at the STT.
Three methods are provided for that purpose:
First, for each sequence you can count the longest guide page for that particular sequence, and then add sufficient null packets to the end of each other guide page so that all the guide pages become the same lengths. Then add the switching packets at the end of the sequence, after all the null packets.
The second method requires buffering of all the packets for all guide pages for each sequence. If this is allowed in the considered system, then the packets can be ordered in the transport stream such that the packets for each guide page appear at slightly higher or lower frequencies, so that they all finish at the same point. Then the switching packets are added at the end of each stream without the null padding.
A third method is to start each sequence together, and then wait until all the packets for all the guide pages have been generated. Once the generation of all packets is completed, switching packets are placed in the streams at the same time and point in each stream.
Depending on the implementation of STT decoder units and requirements of the considered application, each one of the methods can be applied with advantages. For example, the first method, which is null-padding, can be applied to avoid bursts of N packets of the same PID into a decoder's video buffer faster than the MPEG specified rate (e.g., 1.5 Mbit).
The same principles of splicing and synchronization techniques are applicable to a plurality of different transport stream forms, including recombinant stream.
The teachings of the above three methods can be extended apply to similar synchronization problems and to derive similar methods.
The subscriber equipment 106 is connected to the network 104 and receives the transport stream from the network 104. A demodulator/decoder 124 in each of the terminals extracts the transport stream from the modulation, demultiplexes the bitstreams within the transport stream, and decodes a selected program guide video sequence. Since the program guide bitstreams are contained in the transport stream, the terminal selects a particular program guide using its unique packet identifier (PID) that causes a video demodulator/decoder 124 to decode the program guide bitstream identified by that PID (or PIDs in the case of slice based encoding). When the user selects another program guide, another stream is decoded based upon the newly selected PID or PIDs. By transmitting many program guide streams in a common transport stream and by frame locking the program guide source, encoding and decoding processes, the latency experienced as a subscriber selects one guide page after another is undetectable. Also, because the informational video is the same and frame synchronized in each program guide bitstream with the only difference being a different guide graphic, the subscriber sees a transition in the guide graphic, but the informational audio and video is seamlessly presented to the viewer.
More specifically, the background imagery vs1 and the first informational video vs2 are coupled to the serial-to-parallel converter module 300. The frames of each of these video signals are then coupled to the compositor 302. In operation, the compositor 302 synchronizes the frames, resizes the informational video to fit into a predefined rectangular region, positions the rectangular region on the background and merges the two video frame sequences. The controller 114 of
The composited video sequence containing the background and first informational video is then coupled to the second compositor 306 such that the second informational video is composited onto the background and first video. The third compositor 308 performs a similar function to produce a frame sequence having the background and three informational video sequences composited into a single sequence. The size and position of the informational video display regions is controlled by signals from the controller via the PCI bus 312. The output sequence from the third compositor 308 is optionally coupled to the parallel-to-serial converter module 310 to produce a serial bitstream. Generally, the parallel data is coupled directly to the IPG grid compositors (202 in
Each of the IPG graphics, e.g., fifteen, are separately composited in this manner with the background and the advertising. As such, fifteen separate bitstreams, one contains each IPG graphic, are encoded and arranged in the transport stream.
When the subscriber reaches the bottom of the IPG graphic, i.e., the last cell or a special icon (arrow), a different PID is selected for decoding, i.e., the PID for the next IPG page containing channels 11 through 20. The decoder begins decoding the next stream as soon as it is selected. The connection between IPG pages is a functional attribute that is generally transmitted to the subscriber equipment as user data within the transport stream. Since the background and the informational video were synchronously added to the video sequence that become the IPG pages, the informational video seamlessly transitions from one screen to another without any visible anomalies. The IPG graphic is the only portion that changes from 510 1 to 510 2. The process of transitioning from one IPG page to another can be accomplished by incrementing or decrementing through the IPG pages. Additionally, parallel pages may be available to display additional time slots. As such, IPG pages representing programming in other time periods could be accessed by, for example, left and right arrows. These parallel pages may be carried in additional transport streams or in the same transport stream.
A second illustrative IPG page layout 600 is shown in
Although the foregoing description illustratively disclosed encoding an IPG page, the invention finds use in encoding any form of mixed graphical and video information screens. For example, the invention can be used to encode a HTML web page in the graphics region and a related television program in the video region. Alternatively, the informational video can be a television program that is displayed within a program guide while a viewer reviews the schedule information. Selecting the video region would enlarge the video to the entire screen, while selecting a program title in the program guide may initiate a preview video to play in second video window. As such, the invention should be interpreted as encompassing any combination of video and graphics that is encoded as a digital bit stream and broadcast from a head end of an information distribution system.
Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.