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Technique to Quickly, Completely Decode Minimally Represented I Pictures for MPEG-2 Video

IP.com Disclosure Number: IPCOM000005036D
Publication Date: 2001-Aug-01
Document File: 5 page(s) / 137K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a technique to quickly, completely decode minimally represented I pictures for MPEG-2 video.

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Technique to Quickly, Completely Decode Minimally Represented I Pictures for MPEG-2 Video

Disclosed is a technique to quickly, completely decode minimally represented I pictures for MPEG-2 video.

MPEG-2 video is used to convey still content. In some applications, particularly DVDs, still video pictures must be decoded completely and displayed with relatively little delay. A conventional hardware and software acceleration technique used with normal, moving playback is to locally buffer raw MPEG-2 data. The word length chosen for this optimization can be large enough to prevent decoding of a minimally represented still picture.

The disclosed technique describes a solution specific to DVD and other applications that maintain both complete decodability of standalone still pictures and high performance. The disclosed technique is applicable only to specific kinds of still pictures?MPEG-2 I pictures. The technique switches a portion of the decoder parser between high-performance and low-performance versions. The high-performance version is used for most of the decoding process. The low-performance but low-delay version is used for the very end of a picture. This combination enables full high-performance decode of standalone I pictures.

Glossary

MPEG-2 Video ISO/IEC 13818-2: Generic coding of moving pictures and associated audio information: video.

MPEG-2 Video I picture: A syntactical structure within MPEG video that contains intra coded information. Used for resynchronization and still pictures.

Still picture: A picture coded with presentation time of longer duration than a typical video frame; DVD menus and the DVD FBI Warning are examples where still pictures are used.

Minimally coded: A picture represented with the minimum number of bytes according to the MPEG-2 Video specification.

Macroblock: A syntactical structure within MPEG video that refers to a small rectangular region of a video picture

Technology Description

A typical MPEG-2 video decoder is illustrated in Figure 1. Compressed MPEG-2 video elementary streams or program streams received or read by the decoder are parsed for MPEG syntactical elements. This syntax is layered. The smallest, uniquely presentable time unit of the stream is a picture. Passing groups of compressed bits to various parsers processes the picture. Parsed data is further processed and used to form the image data of a picture. After decode (sometimes immediately), this picture is displayed. The coded length of a picture is guaranteed to be an integral number of bytes.

One method of performance acceleration is to read and interpret data on some word length, W, larger than 8 bits (see Figure 2). This method significantly improves performance of the Macroblock Parsing and VLD sections in Figure 1. A minimally coded picture is one represented by only N bytes with no following bytes from padding or other pictures....