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Browse Prior Art Database

Limited Quantization Scale Selection for Moving Picture Experts Group Encoders

IP.com Disclosure Number: IPCOM000117571D
Original Publication Date: 1996-Apr-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Linzer, EN: AUTHOR

Abstract

Moving Pictures Experts Group (MPEG) encoding is discretionary -- different encoders produce different bit streams with the same video input. When conventional encoding schemes are used, the video degrades in after multiple encode-decode cycles, which is undesirable in, for example, an editing environment.

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This is the abbreviated version, containing approximately 82% of the total text.

Limited Quantization Scale Selection for Moving Picture Experts Group
Encoders

      Moving Pictures Experts Group (MPEG) encoding is discretionary
-- different encoders produce different bit streams with the same
video input.  When conventional encoding schemes are used, the video
degrades in after multiple encode-decode cycles, which is undesirable
in, for example, an editing environment.

      A conventional MPEG encoder chooses quantization scale for
each macroblock as follows.  (Quantization scale is a number which
determines the quality of the encoding for that macroblock.  There
are 31 legal choices for quantization scale).  The buffer fullness
before the macroblock is encoded, the type of picture (I, P or B)
that the macroblock is in, the variance or other characteristics of
the macroblock itself, and possibly other factors are all used to
determine an appropriate quantization level for the macroblock.  The
legal value of quantization scale closest to that quantization level
is chosen.

      For this invention, only a small subset of the legal
quantization scale values are considered.  (For example, every fourth
value).  For a single encode-decode cycle, making this limitation may
slightly degrade the video.  However, for multiple encode-decode
cycles the encoder will have a much greater likelihood of choosing
the same value of quantization scale chosen in the last cycle, so the
video quality degrades slower.

      A diagram of an encoder...