2008-01-30, 20:14
An exhaustive review of this topic, wth some interesting comclusions, has been posted over in the doom9 forums here:
http://forum.doom9.org/showthread.php?t=133982
Among other significant (and news to me) findings has to do with colorspace signaling in mpeg2 and how to interpret the 'default' (ie not specified) case.
For example, it is pointed out that later / current revisions of the mpeg2 spec changed the language from
"In the case that sequence_display_extension() is not present in the bitstream or colour_description is zero the chromaticity is assumed to be that corresponding to colour_primaries having the value 1."
to
"In the case that sequence_display_extension() is not present in the bitstream or colour_description is zero the matrix coefficients are assumed to be implicitly defined by the application."
Which is a pretty significant change! Significant enough that many tools (such as dgmpgdec) are changing to align themselves with the findings.
The post is a truly awesome consolidation of information from a variety of sources, and covers not only mpeg2, but mpeg1, mpeg4, H264 ...
Well worth the time to read and understand it!
http://forum.doom9.org/showthread.php?t=133982
Among other significant (and news to me) findings has to do with colorspace signaling in mpeg2 and how to interpret the 'default' (ie not specified) case.
For example, it is pointed out that later / current revisions of the mpeg2 spec changed the language from
"In the case that sequence_display_extension() is not present in the bitstream or colour_description is zero the chromaticity is assumed to be that corresponding to colour_primaries having the value 1."
to
"In the case that sequence_display_extension() is not present in the bitstream or colour_description is zero the matrix coefficients are assumed to be implicitly defined by the application."
Which is a pretty significant change! Significant enough that many tools (such as dgmpgdec) are changing to align themselves with the findings.
The post is a truly awesome consolidation of information from a variety of sources, and covers not only mpeg2, but mpeg1, mpeg4, H264 ...
Well worth the time to read and understand it!
