[FFmpeg-user] Does converting to yuv444p by default make sense?

thljcl jiachielee at live.com
Thu Aug 1 14:09:26 CEST 2013

Andy Furniss-2 wrote
> H264 is talking about lossless where input is and output are the same 
> 444 - Y'CbCr - there is no conversion by H264 from RGB as your PNG 
> example would need - that would be done prior to H264 by ffmpeg.
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Speaking of “YCbCr →YCbCr” for H.264 lossless encoding, you obviously did
not read the H.264 

specifications Ed 8.0, did you?
Let me quote directly from H.264 Specifications,
“The source and decoded pictures (frames or fields) are each comprised of
one or more sample arrays:
– Luma (Y) only (monochrome), with or without an auxiliary array.
– Luma and two Chroma (YCbCr or YCgCo), with or without an auxiliary array.
– Green, Blue and Red (GBR, also known as RGB), with or without an auxiliary
– Arrays representing other unspecified monochrome or tri-stimulus colour
samplings (for example, YZX,
also known as XYZ), with or without an auxiliary array.”
That is at Page 42.
On Page 25, I quote
“With the exception of the transform bypass mode of operation for lossless
coding in the High 4:4:4 

Intra, CAVLC 4:4:4 Intra, and High 4:4:4 Predictive profiles, and the I_PCM
mode of operation in all profiles, the algorithm is typically not lossless,
as the exact source sample values are typically not preserved through the
encoding and decoding processes.”

Also look at Page 408 at Table E-3 - Color Primaries 

“The same 444”? Yeah, considering that sRGB is also regarded as 444

H.264 specification explicitly says that the source is image encoded in
sRGB. Anything to you want say to response?

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