Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Utility Patent
1997-09-19
2001-01-02
Garber, Wendy (Department: 2712)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C370S394000
Utility Patent
active
06169843
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to recording and playback of hierarchically organized audio-video signals. More particularly, the present invention relates to recording and playback of transport packets in a transport stream which includes multiplexed audio and video data streams from one or more data sources or programs.
BACKGROUND OF THE INVENTION
Many digital multimedia applications require efficient compression and transmission of video and audio information. A recently-developed international standard for compression and transmission of video and audio data streams is commonly known as MPEG-2. The MPEG-2 standard was developed by the International Standards Organization (ISO) Moving Pictures Experts Group (MPEG) and is documented in ISO/IEC DIS 13818-1, “Information Technology-Generic Coding of Moving Pictures and Associated Audio Information: Systems,” ISO/IEC DIS 13818-2, “Information Technology-Generic Coding of Moving Pictures and Associated Audio Information: Video” and ISO/IEC Committee Draft 13818-3, “Information Technology-Generic Coding of Moving Pictures and Associated Audio Information: Audio.” The above-cited ISO documents are incorporated herein by reference. The MPEG-2 systems specification provides a multi-layer hierarchical organization for multiplexing and transmission of video, audio and other types of program data streams, and is described in greater detail in A. Wasilewski, MPEG-2 Systems Specification: Blueprint for Network Interoperability,
COMM. TECH.,
Feb., 1994, which is incorporated by reference herein. The MPEG-2 video and audio specifications provide compression and encoding of video and audio data streams. MPEG-2 video compression is described in greater detail in D. Le Gall, MPEG: A Video Compression Standard for Multimedia Applications,
COMMUNICATIONS OF THE ACM,
April 1991, which is incorporated by reference herein.
The systems aspects of the MPEG-2 standard generally involve multiplexing several elementary streams from one or more programs to form a higher level packet-based stream. A given program may correspond to one or more television or motion picture signals and may include multiple elementary streams in the form of separately-encoded compressed video and audio data streams, as well as other program data streams such as closed caption text. The higher level packet-based stream in accordance with the MPEG-2 standard may be either a program stream or a transport stream. An MPEG-2 program stream generally carries a single program such that all elementary streams in the program stream share a common time base, while an MPEG-2 transport stream can carry elementary streams from multiple programs with different time bases. An MPEG-2 program stream generally uses variable-length packets and is intended for use in transmission applications with relatively low error rates. An MPEG-2 transport stream generally uses fixed length packets and includes error reduction and detection features.
The program and transport streams associate related elementary data streams for a given program or programs such that the elementary streams can be extracted, decoded and presented together in a coherent fashion. The program and transport streams may be recorded on or played back from a digital video disc (DVD), video tape, magnetic or optical disk drive or other suitable storage device. It should be noted that both program streams and transport streams may be considered part of a transport layer in accordance with the ISO network reference model as set forth in the ISO 7498 standard. The term “transport stream” as used herein is therefore intended to include both MPEG-2 program streams and transport streams as well as other packet-based data streams formed in accordance with non-MPEG standards.
Prior art recording and playback techniques for transport streams may utilize a predetermined constant bit rate to record or play back a transport stream. For example, a prior art video server may include a fixed-rate register structure which transmits or receives transport stream bits at a predetermined bit rate. The server thus delivers the transport stream to a storage device at the predetermined bit rate. Another prior art technique utilizes feedback from a destination device when delivering the transport stream. For example, a prior art video server may interact with a peripheral such as a storage device in a television set-top box to download a transport stream corresponding to a video-on-demand selection. If the rate at which the storage device can receive input data exceeds the transport stream data rate, the server must download the transport stream to the storage device in increments which the storage device can accommodate. The storage device may therefore be required to provide control signals to the server indicating when it is able to accommodate the next increment of the transport stream.
Although these prior art transport stream delivery techniques may be adequate for “off-line” downloading or playback to a single destination, they are generally not well-suited for numerous other multimedia applications in which transport stream data must be recorded and/or played back in real time and broadcast to multiple destinations. The latter include those applications in which transport stream data is to be broadcast via cable, telephone or computer network, satellite or other transmission medium to a number of remote users. For example, accurate real-time playback is generally required in a broadcast application in which commercials or other ads are inserted into a recorded transport stream program such that the recorded program and inserted ads may be broadcast to remote users. Other applications in which prior art recording/playback techniques are inadequate include video server applications with multiple streams at different rates, and playback of “speed changing” variable rate streams. The prior art techniques thus fail to provide adequate recording and playback of transport stream data to and from peripheral storage devices.
It is therefore an object of the present invention to provide improved techniques for recording and playback of transport streams. It is a further object to provide a transport stream recording and playback system which allows real-time recording and playback at rates suitable for use in a wide variety of multimedia applications.
SUMMARY OF THE INVENTION
These and other objects are achieved by the present invention. In accordance with one aspect of the invention, a recording method and apparatus are provided in which an arrival timestamp (ATS) is generated for each of a plurality of input transport packets to be recorded in a peripheral storage device. A given arrival timestamp indicates the arrival time of the corresponding transport packet in the recording system. Each of the plurality of transport packets are then stored with their corresponding arrival timestamps. A record mode of the present invention may also utilize a packet identifier (PID) decoder to perform a packet filtering function such that only incoming transport packets with particular PIDs are stored. The arrival timestamp may be generated using an MPEG-2 system time clock (STC) and may be configured in an MPEG-2 program clock reference (PCR) format. Alternatively, the arrival timestamp may be generated using PCRs included within the incoming transport packets.
Another aspect of the invention involves a playback method and apparatus which utilize arrival timestamps previously stored with a recorded transport packet. A time-corrected playback of previously-recorded transport packets is provided by delivering the transport packets in accordance with the corresponding arrival timestamps. A playback mode of the present invention may also involve detecting a timestamp discontinuity in one or more of the arrival timestamps, and adjusting the playback system time clock accordingly. These aspects of the invention provide improved playback synchronization in a variety of multimedia applications.
A further aspect of the invention involves a null packet in
Hart Sean C.
Johnson Brian
Lenihan Michael P.
Magee Mark
Garber Wendy
Harmonic Inc.
Moe Aung S.
Proskauer Rose LLP
LandOfFree
Recording and playback of audio-video transport streams does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Recording and playback of audio-video transport streams, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Recording and playback of audio-video transport streams will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439443