Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-12-30
2001-04-10
Kelley, Chris S. (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06215822
ABSTRACT:
The present invention relates to digital video decoding, and more particularly, to buffer memory configuration, buffer memory address generation and video decoder implementation for the reproduction of moving pictures from digital signals, such as in broadcast television receiver systems, digital video compact disc playing systems and other digital video presentation systems.
BACKGROUND OF THE INVENTION
Recent times have seen an acceleration in efforts by suppliers of consumer electronics to greatly expand the amount and quality of information provided to users. The expanded use of multimedia information in communications and entertainment systems along with user demands for higher quality and faster presentations of the information has driven the communications and entertainment industries to seek systems for communicating and presenting information with higher densities of useful information. These demands have stimulated the development and expansion of digital techniques to code and format signals to carry the information.
Unlike most of the communication systems of the past, particularly television broadcast systems and other systems used for home entertainment, where analog signals have filled available bandwidths with single program real time signals in a straight forward format that includes much redundant information as well as much humanly imperceivable information, digital transmission systems possess the ability to combine and identify multiple programs and to selectively filter out redundant or otherwise useless information to provide capabilities for the transmission of programs having higher quality or having higher useful information carrying ability or density. As a result of the high technological demand for such capabilities, advances toward the specification and development of digital communications formats and systems have accelerated.
In furtherance of these advances, the industry sponsored Motion Pictures Expert Group (MPEG) chartered by the International Organization for Standardization (ISO) has specified a format for digital video and two channel stereo audio signals that has come to be known as MPEG-1, and, more formally, as ISO-11172. MPEG-1 specifies formats for representing data inputs to digital decoders, or the syntax for data bitstreams that will carry programs in digital formats that decoders can reliably decode. In practice, the MPEG-1 standards have been used for recorded programs that are usually read by software systems. The program signals include digital data of various programs or program components with their digitized data streams multiplexed together by parsing them in the time domain into the program bitstreams. The programs include audio and video frames of data and other information.
An enhanced standard, known colloquially as MPEG-2 and more formally as ISO-13818, has more recently been agreed upon by the ISO MPEG. This enhanced standard has grown out of needs for specifying data formats for broadcast and other higher noise applications, such as high definition television (HDTV), where the programs are more likely to be transmitted than recorded and more likely to be decoded by hardware than by software.
The MPEG standards define structure for multiplexing and synchronizing coded digital and audio data, for decoding, for example, by digital television receivers and for random access play of recorded programs. The defined structure provides syntax for the parsing and synchronizing of the multiplexed stream in such applications and for identifying, decoding and timing the information in the bitstreams.
The MPEG video standard specifies a bitstream syntax designed to improve information density and coding efficiency by methods that remove spacial and temporal redundancies. For example, the transformation blocks of 8×8 luminance pels (pixels) and corresponding chrominance data using Discrete Cosine Transform (DCT) coding is contemplated to remove spacial redundancies, while motion compensated prediction is contemplated to remove temporal redundancies. For video, MPEG contemplates Intra (I) frames, Predictive (P) frames and Bidirectionally Predictive (B) frames. The I-frames are independently coded and are the least efficiently coded of the three frame types. P-frames are coded more efficiently than are I-frames and are coded relative to the previously coded I- or P frame. B-frames are coded the most efficiently of the three frame types and are coded relative to both the previous and the next I- or P-frames. The coding order of the frames in an MPEG program is not necessarily the same as the presentation order of the frames. Headers in the bitstream provide information to be used by decoders to properly decode the time and sequence of the frames for the presentation of a moving picture.
The video bitstreams in MPEG systems include a Video Sequence Header containing picture size and aspect ratio data, bit rate limits and other global parameters. Following the Video Sequence Header are coded groups-of-pictures (GOPs). Each GOP usually includes only one I-picture and a variable number of P- and B-pictures. Each GOP also includes a GOP header that contains presentation delay requirements and other data relevant to the entire GOP. Each picture in the GOP includes a picture header that contains picture type and display order data and other information relevant to the picture within the picture group.
Each MPEG picture is divided into a plurality of Macroblocks (MBs), not all of which need be transmitted. Each MB is made up of 16×16 luminance pels, or a 2×2 array of four 8×8 transformed blocks of pels. MBs are coded in Slices of consecutive variable length strings of MBs, running left to right across a picture. Slices may begin and end at any intermediate MB position of the picture but must respectively begin or end whenever a left or right margin of the picture is encountered. Each Slice begins with a Slice Header that contains information of the vertical position of the Slice within the picture, information of the quantization scale of the Slice and other information such as that which can be used for fast-forward, fast reverse, resynchronization in the event of transmission error, or other picture presentation purposes.
The Macroblock is the basic unit used for MPEG motion compensation. Each MB contains an MB header, which, for the first MB of a Slice, contains information of the MB's horizontal position relative to the left edge of the picture, and which, for subsequently transmitted MBs of a Slice, contains an address increment. Not all of the consecutive MBs of a Slice are transmitted with the Slice.
The presentation of MPEG video involves the display of video frames at a rate of, for example, twenty-five or thirty frames per second (depending on the national standard used, PAL or NTSC, for example). Thirty frames per second corresponds to presentation time intervals of approximately 32 milliseconds. The capacity of MPEG signals to carry the information necessary for HDTV and other presentations providing high resolution video is achieved in part by exploiting the concept that there is typically a high degree of correlation between adjacent pictures and by exploiting temporal redundancies in the coding of the signals. Where two consecutive video frames of a program are nearly identical, for example, the communication of the consecutive frames requires, for example, only the transmission of one I-picture along with the transmission of a P-picture containing only the information that differs from the I-picture, or Reference Picture, along with information needed by the decoder at the receiver to reconstruct the P-picture from the previous I-picture. This means that the decoder must have provision for storage of the Reference Picture data.
Information contained in a P-picture transmission includes blocks of video data not contained in a Reference I- or P-picture as well as data needed to relocate in the picture any information that is contained in the previous I- or P-picture that has moved. The technique use
Bose Subroto
Gadre Shirish C.
Ozcelik Taner
Reza Syed
Kelley Chris S.
Sony Corporation
Vo Tung
Wood Herron & Evans L.L.P.
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