102 What is the TM (Test Model) ? What is the TM rate control and adaptive quantization technique ? (MPEG-2)
Description
This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
102 What is the TM (Test Model) ? What is the TM rate control and adaptive quantization technique ? (MPEG-2)
The Test model (MPEG-2) and Simulation Model (MPEG-1) were not, by
any stretch of the imagination, meant to epitomize state-of-the art
encoding quality. They were, however, designed to exercise the syntax,
verify proposals, and test the relative compression performance of
proposals in a timely manner that could be duplicated by
co-experimenters. Without simplicity, there would have been no doubt
endless debates over model interpretation. Regardless of all else,
more advanced techniques would probably trespass into proprietary
territory.
The final test model for MPEG-2 is TM version 5b, a.k.a. TM version 6,
produced in March 1993 (the time when the MPEG-2 video syntax was
frozen). The final MPEG-1 simulation model is version 3 (SM-3). The
MPEG-2 TM rate control method offers a dramatic improvement over the SM
method. TM adds more accurate estimation of macroblock complexity
through use of limited a priori information. Macroblock quantization
adjustments are computed on a macroblock basis, instead of
once-per-macroblock row (which in the SM-3 case consisted of an entire
slice).
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