101 Is the encoder standardized ? (MPEG-2)
Description
This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
101 Is the encoder standardized ? (MPEG-2)
The encoder rests just outside the normative scope of the standard,
as long as the bitstreams it produces are compliant. The decoder,
however, is almost deterministic: a given bitstream should reconstruct
to a unique set of pictures. However, since the IDCT function is the
ONLY non-normative stage in the decoder, an occasional error of a Least
Significant Bit per prediction iteration is permitted. The designer is
free to choose among many DCT algorithms and implementations. The IEEE
1180 test referenced in Annex A of the MPEG-1 (ISO/IEC 11172-2) and
MPEG-2 (ISO/IEC 13818-2) Video specifications spells out the
statistical mismatch tolerance between the Reference IDCT, which is a
separable 8x1 "Direct Matrix" DCT implemented with 64-bit floating
point accuracy, and the IDCT you are testing for compliance.
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