Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2000-08-31
2002-09-17
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06453115
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of encoding and storing moving pictures and audio signals and, in particular, a system for digitally encoding, storing, and displaying a video stream in MPEG format on a personal video recorder (PVR) hard drive in a manner that facilitates play modes other than standard speed, sequential play.
2. Description of the Related Art
Personal Video Recorders (PVRs), also sometimes called Digital Video Recorders (DVRs), are digitally based devices that enable a viewer of television to receive and digitally record video programming, such as TV broadcasts, movie downloads, and the like, for more flexible viewing. For example, PVRs enable a viewer to record defined categories of live television programming over the course of days. The viewer may stipulate that they want to record a series of tennis matches, all nature shows, or all episodes of a particular show over the course of a season. PVRs also enable a person viewing a “live” television broadcast to pause viewing and, at a later time, resume viewing the broadcast from the point at which live viewing was paused. A viewer also has the option to skip portions of a broadcast, such as for example commercials, upon reviewing a broadcast by employing a PVR. The recording features of PVRs can be performed when the viewer is away from the PVR so that the viewer can view preferred programs at a time that is convenient.
PVRs can receive either a streaming analog signal in an uncompressed format or a digitally encoded signal, such as an MPEG signal, from a transmission source. If the PVR receives an analog signal such as a television signal in an uncompressed format, the PVR typically digitally encodes the signal, stores the digitally encoded signal in a compressed format, and decodes and presents the signal for subsequent viewing. Similarly, if the PVR receives an already digitally encoded signal, the PVR then stores the signal and decodes and presents the signal for subsequent viewing. PVRs currently typically include 13.6-gigabyte hard disks that offer up to 14 hours of video programming or 27.2-gigabyte disks that offer up to 30 hours of programmable viewing.
One common compression standard used for video streams currently used today is known as MPEG. MPEG is a standard for digitally encoding moving pictures and interleaved audio signals. MPEG facilitates compressing a video stream to reduce the storage capacity and transmission bandwidth required for an MPEG stream as compared to an uncompressed video stream. In a typical video stream, adjacent individual video frames will have much in common with the preceding and subsequent frames. For example, from one individual still frame of a scene to the next, much of the background, the colors, and the luminous intensity will usually remain the same. A relatively small amount of the overall scene will typically change from frame to frame. The compression technique used with MPEG leverages this redundancy of video in both the spatial and temporal dimensions in order to define certain frames with respect to other frames in a dependent or anticipatory manner and thereby reduce the amount of information required to accurately define a video stream.
In particular, the MPEG standard defines three types of frame formats: Intra-coded reference frames (I), Predictive-coded frames (P), and Bi-directionally predictive-coded frames (B). I frames contain all of the information required for a single video frame and are thus independent frames that need no information from other frames either before or after for decoding. On the other hand, P frames are defined with respect to preceding I frames or other P frames. B frames are bi-directionally defined with respect to both preceding and subsequent frames in the MPEG stream. Thus, both P and B frames need information from surrounding frames for decoding; a P or B frame by itself cannot be decoded into a viewable image. The I-, P-, and B- frames are organized into at least one sequence defined by a sequence header and a set of subsequent I, P, and B frames. The sequence header contains display initialization information defining picture size and aspect ratio, frames and bit rate, decoder buffer size, and chroma pixel structure and may contain optional quantizer matrices and/or user data.
While digital video compression schemes, such as MPEG, reduce the storage and transmission bandwidth required for these digital video streams, these compression schemes result in video data that is not readily adaptable to non-standard modes of display. For example, viewers of video images like to be able to use TrickPlay modes of viewing including by way of example: fast forward, reverse play, skip ahead, skip back, etc. Generally, compressed video streams that have inter-frame dependencies, such as MPEG streams, are not readily suited to random access of different frames within the stream as is often required for TrickPlay modes of viewing.
For example, with an MPEG file, fast forward or fast reverse viewing of the full stream is not efficient because such modes of operation would still require the decoding of each of the P and B frames, which, in turn, may require decoding of multiple other frames. Hence, fast forward and fast reverse manners of display are not easily achievable due to the memory and processing required for the decoding of multiple frames that must be accomplished to reassemble the compressed data. Moreover, skipping to a particular segment within a video stream is also complicated by the fact that the particular segment desired may correspond to an interdependent frame which requires the decoding of multiple other frames before the desired frame can be viewed.
Hence, the MPEG compression standard as used to facilitate efficient transfer and storage of digital video data inhibits subsequent flexible viewing of the digital video data. As more flexible viewing of digital video data is highly desirable, several mechanisms for implementing TrickPlay type viewing of compressed video data have been developed.
In one example, the compressed video streams are pre-recorded onto high-density recording media in a manner that facilitates TrickPlay. One example of this is disclosed in U.S. Pat. No. 6,002,834 to Hirabayashi, et al. In Hirabayashi, MPEG files are recorded onto optical disks along with an index table indicating the memory locations of the intra-coded reference (I) frames. The index table can then be subsequently used to implement TrickPlay. While Hirabayashi facilitates the use of TrickPlay with compressed video data, Hirabayashi provides the video data on a fixed recording medium, i.e., an optical disk, wherein the data necessary to implement TrickPlay has been previously recorded.
Video signals are typically provided to PVRs as either uncompressed analog signals or digitally compressed signals such as the signals received via cable or satellite television systems. While some streaming systems have been disclosed that provide video streams with redundant streams to facilitate TrickPlay (See, e.g., U.S. Pat. No. 6,065,050 to De Money), many video streams are provided as analog signals or simple MPEG files that do not have any pre-recorded files or formats for facilitating TrickPlay.
Hence, there is a need for a system for recording compressed video data in a manner that facilitates flexible display of the compressed video data. To this end, there is a need for a system that can receive a stream of video data, such as a cable or satellite television broadcast, via an interface and compress and store the signals so as to be able to implement TrickPlay of the compressed video data without requiring that the compressed video data include pre-encoded data for TrickPlay.
SUMMARY OF THE INVENTION
In one aspect, the invention comprises a digital video recording system for storing, retrieving and displaying compressed digital video data. The system comprises a video stream buffer system that receives a stream of digital video data comprising intra-coded reference frames and predi
Keen Personal Media, Inc.
Onuaku Christopher
Shara, Esq. Milad G.
Tran Thai
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