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Old 11 November 2016, 19:35   #74
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Join Date: May 2016
Location: Rostock/Germany
Posts: 53
Originally Posted by pandy71 View Post
MPEG-1 fully support YCgCo (just set matrix coefficient as 8 - normally it is reserved for future use in MPEG-1 and MPEG-2 but it is fully specified for H.264 and H.265 - problem is that nobody use MPEG-1 so it is uncommon practice to use YCgCo as it is not popular even nowadays but Amiga have limited processing capabilities so any gain is valuable (as every pixel need to be converted from YCbCr to RGB and later to Amiga HW limitations).
Side to this Intra frame formats should be less intensive especially H.264 (without CABAC and deblocking loop which takes like 50 - 60% of decoder processing power).
I can made streams for testing if this is a problem.
Well, the YCgCo color space is certainly appealing, not only for the lossless properties but also decorrelation abilities along with simple computation.

In terms of H.264, I'm not sure whether it would really help to save cycles on a humble 68k. Correct me if I'm wrong and missed an amendment to AMD 1, but FRExt states that YCoCg is legal only with chroma_format_idc=3, i.e. 4:4:4 and at least 9 Bit for Chroma in H.264. So when the effective pixel count doubles and 8 BPP is no longer sufficient for storage, the resulting tradeoff might well swing in an unfortunate direction (when staying standards-compliant).
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