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

Andy Furniss adf.lists at gmail.com
Thu Aug 1 12:12:10 CEST 2013

thljcl wrote:

> In the current specification (Ed 8.0), there are three profiles of H.264
> that support lossless coding. Among those three, one of them, which is High
> 4:4:4 Predictive, is currently implemented by x264, which is used by ffmpeg
> as H.264 encoder.
> Poynton’s article you mentioned at
> http://www.poynton.com/papers/Discreet_Logic/index.html was published on
> July 28, 1997; it was a time not even the first edition of H.264
> Specification was published.
> It’s fair to say that while some statements stated by him at the time remain
> valid today, considering the pace of change in technology, we cannot take
> everything he stated at the time for granted today.
> Whether or not -pix_fmt “yuv444p” is required to be specified explicitly
> when it comes to lossless coding depends on the sources, if sources are PNG
> images, “yuv444p” would be chosen automatically. If not, you may need to
> specify “yuv444p” for lossless coding.
> As usual, you do not have to take my words for granted. Go to
> http://www.itu.int/ITU-T/recommendations/rec.aspx?rec=6312 read the H.264
> specifications yourself. The current edition as well as the past editions
> are all available online. You can verify yourself whether I said is true or
> not.
> Of course, you can claim that the lossless coding in H.264 is not “truly
> lossless”. If you can submit proofs to prove your case, many other people
> and I will be glad to accept the truth. Until then, let us the accept the
> currently known theories.

Well you maths is better than mine, and the effort you put into 
presenting your case is hugely more than me, but -

You don't seem to have listened to what Nicolas said and now above you 
seem to to be comparing something totally un-related to what was stated 
in the Poynton paper.

He is talking about full range RGB to 601 studio levels Y'CbCr, but the 
stuff about lossless H264 above has  absolutely nothing to do with that.

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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