Television – Bandwidth reduction system – Data rate reduction
Patent
1997-12-30
1999-02-23
Chin, Tommy P.
Television
Bandwidth reduction system
Data rate reduction
348515, 370538, 375355, H04N 712
Patent
active
058749977
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates generally to the technical field of recorded and/or transmitted compressed digital data, and, more particularly, to enabling a subsequent synchronized presentation of video and audio data as they are combined into a single compressed digital data stream.
BACKGROUND ART
Proper reproduction of a recorded and/or transmitted multimedia program, consisting of compressed digitized video data accompanied by associated compressed digitized audio data, requires combining two independent digital data bitstreams into a single, synchronized, serial system data stream that includes both video and audio data. Lack of or an improper synchronization of the video and audio data in assembling the data into the system data stream, or in decoding and presenting an assembled system data stream, frequently causes a visible image to appear out of synchronization with accompanying sound. For example, a presentation of images showing lip movements of an individual speaking words may not be synchronized with the audible sound of those words.
To address the preceding issue, Part 1 of the Moving Pictures Experts Group ("MPEG") standard, International Organization for Standardisation ("ISO") and International Electrotechnical Commission ("IEC") standard ISO/IEC 11172, defines a framework which permits combining-bitstreams of digitized video and audio data into a single, synchronized, serial system data stream. Once combined into a single digital data stream, the data is in a form well suited for digital storage, such as on a hard disk or CD-ROM included in a digital computer, or for transmission, such as over a cable antenna television ("CATV") system or high bit rate digital telephone system, e.g. a T1, ISDN Primary Rate, or ATM digital telecommunications access. A system data stream assembled in accordance with the ISO/IEC 11172 standard may be decoded by an MPEG decoder to obtain decoded pictures and/or decoded audio samples
The ISO/IEC 11172 standard defining MPEG compression specified that packets of data, extracted from the compressed video bitstream and from the compressed audio bitstream, are to be interleaved in assembling the system data stream. Furthermore, in accordance with the ISO/IEC 11172 standard a system data stream may include private, reserved and padding streams in addition to compressed video and compressed audio bitstreams. While properties of the system data stream as defined by the MPEG standard impose functional and performance requirements on MPEG encoders and decoders, the system data stream specified in the MPEG standard does not define an architecture for or an implementation of MPEG encoders or decoders. In fact, considerable degrees of freedom exists for possible designs and implementations of encoders and decoders that operate in accordance with the ISO/IEC 11172 standard.
A system data stream in accordance with Part 1 of the ISO/IEC 11172 standard includes two layers of data; a system data layer which envelopes digital data of a compression layer. The ISO/IEC 11172 system layer is itself divided into two sub-layers, one layer for multiplex-wide operation identified as the "pack layer," and one for stream-specific operations identified as the "packet layer." Packs, belonging to the pack layer of a system data stream in accordance with the ISO/IEC 11172 standard, include headers which specify a system clock reference ("SCR"). The SCR fixes intended times for commencing decompression of digitized video and audio data included in the compression layer in a period of 90 kilohertz ("kHz").
To effect synchronized presentation of digitized video and audio data, the ISO/IEC 11172 standard defining the packet layer provides for "presentation time-stamps" ("PTS") and also optional decoding time-stamps ("DTS"). The PTS and DTS specify synchronization for the video and audio data with respect to the SCR specified in the pack layer. The packet layer, which optionally contains both the PTS and DTS, is independent of the data contained in the compression layer defined
REFERENCES:
patent: 4734764 (1988-03-01), Pocock et al.
patent: 4847690 (1989-07-01), Perkins
patent: 4849817 (1989-07-01), Short
patent: 5053860 (1991-10-01), Tsinberg
patent: 5231492 (1993-07-01), Dangi et al.
patent: 5323396 (1994-06-01), Lokhoff
patent: 5481543 (1996-01-01), Veltman
Chin Tommy P.
FutureTel, Inc.
Philippe Gims
Schreiber Donald E.
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