112 What does it mean to be compliant with MPEG ? (MPEG-2)
Description
This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
112 What does it mean to be compliant with MPEG ? (MPEG-2)
There are two areas of conformance/compliance in MPEG:
1. Compliant bitstreams
2. Compliant decoders
Technically speaking, video bitstreams consisting entirely of I-frames
are syntactically compliant with the MPEG specification. The I-frame
sequence simply utilizes a rather limited subset of the full syntax.
Compliant bitstreams must obey the range limits (e.g. motion vectors
ranges, bit rates, frame rates, buffer sizes) and permitted syntax
elements in the bitstream (e.g. chroma_format, B-pictures, etc).
Decoders, however, must be able to decode all combinations of legal
bitstreams.. For example, a decoder which is incapable of decoding P or
B frames is definitely not a Main Profile or Constrained Parameters
decoder! Likewise, full arithmetic precision must be obeyed before any
decoder can be called "MPEG compliant." The IDCT, inverse quantizer,
and motion compensated predictor must meet the accuracy requirements
defined in the MPEG document. Real-time conformance is more complicated
to measure than arithmetic precision, but it reasonable to expect that
decoders that skip frames on reasonable bitstreams are not likely to be
considered compliant.
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