#11254: "-sws_dither" seemingly ineffective
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Reporter: | Type: defect
MasterQuestionable |
Status: new | Priority: important
Component: swscale | Version: git-
| master
Keywords: sws_dither | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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͏ The option appears recognized from the debug output.
͏ And indeed affecting threading:
[swscaler] Error-diffusion dither is in use, scaling will be single-
threaded.
͏ .
͏ But the output doesn't appear influenced: as if fixed to certain
predefined dither.
͏ Testing the [ https://trac.ffmpeg.org/wiki/colorspace#yuv444p ] e.g.
͏ `ffmpeg -y -v trace -hide_banner -nostdin -nostats -i
"origin(rgb24).webp" -pix_fmt yuv444p -sws_dither none -sws_flags
spline+accurate_rnd+full_chroma_int -color_range 1 -colorspace 5
-color_primaries 5 -color_trc 6 -c:v libx264 -preset placebo -qp 0
-x264-params "keyint=15:no-deblock=1" "yuv444p.avi"`
͏ ; etc.
͏ Trying every possible value of "-sws_dither" in:
͏ https://ffmpeg.org/ffmpeg-scaler.html
͏ ; resulted identical output.
͏ Which is likely unsensible.
͏ The converted WebP ("yuv444p.webp") also indicated certain dither in-
use: file size bigger than original ("origin(rgb24).webp").
͏ See also: https://trac.ffmpeg.org/ticket/11182#comment:16
͏ .
͏ Such conversion without dither tends to make colors more similar:
thus improve compressibility.
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Ticket URL: <https://trac.ffmpeg.org/ticket/11254>
FFmpeg <https://ffmpeg.org>
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