Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2001-05-07
2004-05-18
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240260
Reexamination Certificate
active
06738427
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the compression, cataloging and viewing of full motion videos and, more particularly, to the processing of compressed video data.
2. Description of Related Art
The infrastructure and process required to create and operate a video archive in the digital domain are well known in the broadcast video industry. The archiving process generally begins by digitizing and compressing the analog video using MPEG-1 or MPEG-2 compression, then moving the compressed video file to a long term storage. To preserve the contribution quality of the video, broadcasters generally select a high compressed bitrate (i.e., 15-40 Mbps), which allows the original video to be recovered with relatively high fidelity in spite of the lossiness of the MPEG compression scheme.
The high bitrate of the compressed video, however, presents considerable problems to the broadcaster's local area network and computer workstation infrastructure, when the video must be distributed for viewing and post-production work. The high network bandwidth and the amount of time required to transfer the assets throughout the plant places an upper limit on the number of concurrent transfers and severely constrains productivity. In response to this bandwidth problem, broadcasters create an additional copy of the video at a much lower compressed bitrate (i.e., 1.5-4 Mbps). This low bitrate file, referred to as a ‘proxy’ or ‘browse’ file, enables users to quickly download the video or to view it directly on computer monitors by utilizing a streaming video server. To facilitate the viewing of video assets outside the local area network, a second proxy file is often encoded at a very low bitrate (56-1000 Kbps), for streaming over low speed terrestrial lines.
After ingestion of the video, the next step in the archiving process is to create an entry for the video in the video library catalog. This entry contains metadata, which is information pertinent to the video. The contents and format of a video catalog record, normally broadcaster unique, facilitate the search and retrieval of video clips within the broadcaster's video library. Presently, there are commercially available video catalog applications (catalogers) that will automatically extract from an MPEG-1 or MPEG-2 video file metadata, such as closed caption text and the text of the actual audio program, obtained via speech recognition technology. Catalogers further extract metadata from the video by performing scene change analysis and creating a bitmap of the first frame after each cut or major scene transition. These bitmaps, referred to individually as a ‘thumbnail’ or collectively as a storyboard, are considered essential metadata because they enable the end user to determine very quickly the video content. Absent the storyboard, the end user is forced to view the video or, at a minimum, fast forward through a video, to find the desired video segment. An additional feature of prior art catalogers is the capability to randomly access and play the proxy video file by double clicking on a storyboard thumbnail.
Further productivity gains can be achieved if the proxy file is a replica of the high-resolution video, where both files begin on the same video frame and have equal duration. When the browse file is a true proxy, a video production engineer is able to import several proxy files into a video editor and produce a program, creating an edit decision list (EDL). This EDL is subsequently exported to a high quality video editing suite that downloads the high-resolution version of the videos from the archive and executes the EDL to produce the air-ready material. Ideally, the broadcast editing suite retrieves from the broadcast server or archive only those segments of the high-resolution file that are specified in the EDL.
Producing a high-resolution video and one or more frame accurate proxy files is problematic because two or more MPEG encoders and a source playout device must be started frame accurately, and the encoders must be capable of extracting SMPTE timecode from the vertical blanking interval and storing the timecode in the MPEG Group of Pictures (GOP) header, although some broadcasters may allow the encoders to encode alternately the locally produced house SMPTE timecode. Moreover, the encoders must not drop or repeat any frames during the encoding process, and the encoders must stop on the same video frame.
Although there are commercially available MPEG encoders that are capable of producing such proxy files, these encoders are very expensive and are not economical for a broadcaster planning to operate many ingest stations. Moreover, these high-end encoders store the MPEG data in a vendor proprietary elementary stream format, which makes them uninteroperable with other MPEG decoders. Thus, video files sent to another broadcast facility must be first remultiplexed into a MPEG compliant format. Moreover, it is undesirable from a business perspective to use a nonstandard storage format. Furthermore, video quality and reliability are the normal criteria for selecting an encoder vendor. Clearly, a need exists to create proxy files using good quality, but less capable, MPEG encoders. An encoder that fails to store SMPTE time in the GOP header, for example, should not be eliminated from consideration, if it meets all other broadcaster requirements.
There is a obviously a need for recording SMPTE timecodes. However, there are problems that occur when dealing with recording timecodes. There are two timecodes associated with every video: an absolute and relative timecode. The absolute timecode is the SMPTE timecode recorded as the video is being shot. It usually reflects the actual time of day, but if the camera operator fails to properly set the SMPTE timecode generator on the camera, it may indicate any random clock time. Reporters and producers taking notes will record the SMPTE timecode while filming, to enable them to quickly find important footage during post-production. It is for this reason that many archive librarians insist on preserving the absolute timecode as essential metadata when compressing and cataloging video. However, the absolute timecode on a source video tape can be anomalous (e.g., missing, discontinuous, jump backwards in time, non-incrementing, non-drop frame mode, etc.).
The relative timecode is a timecode that is relative to the start of the video, and is often referred to as elapsed time. Many producers prefer to use relative timecode instead of absolute timecode during editing sessions, because it can simplify the arithmetic associated with calculating video clip duration. More importantly, it is more dependable than the absolute timecode.
The syntax and semantics of MPEG-2 are described in detail in the Moving Pictures Expert's Group (MPEG) standard entitled Coding of Moving Pictures and Associated Audio ITU Recommendation H.262, which is incorporated herein by reference. One of the shortcomings of the MPEG standard is that only one timecode is recorded, and this timecode is placed in the GOP header that typically occurs every 12-15 frames. Thus, if the absolute timecode abruptly changes between the two GOP headers, the change in SMPTE time is not registered until the next GOP header, and therefore the MPEG file does not accurately reflect the absolute timecode of the source. This mismatch in SMPTE time would result in EDL errors, if absolute timecode were to be used when editing with the proxy file. Some vendor MPEG encoders are capable of recording the timecode of each frame in a user defined data field within the video data. However, there is no standard for formatting these data, and only the vendor's own decoder is capable of decoding the user data packets. Therefore, there is a present need for encoding both absolute and relative timecode into a proxy file on a frame basis, which will accurately reflect the timecodes of the associated high-resolution video file.
There is also a need for recording timecodes in non-proxy files.
Bugg George A
International Business Machines - Corporation
Kelley Chris
Parker Esq. Sandra M.
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