[FFmpeg-trac] #3785(swscale:closed): SWSCALE: in_range, in_color_matrix, out_range, out_color_matrix incorrect
FFmpeg
trac at avcodec.org
Sat Apr 24 02:33:14 EEST 2021
#3785: SWSCALE: in_range, in_color_matrix, out_range, out_color_matrix incorrect
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Reporter: troy_s | Owner: (none)
Type: defect | Status: closed
Priority: normal | Component: swscale
Version: git-master | Resolution: invalid
Keywords: range | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Changes (by Balling):
* resolution: needs_more_info => invalid
Comment:
>BT.709 and sRGB share identical luminance coefficients
sRGB does not have luminance coefficients at all, since it is RGB. sYCC
does. And no, sYCC uses BT.601 matrix. Same about Adobe RGB (opRGB) and
Adobe YCC (opYCC) (BT.601 matrix too) and CMYK vs. YCCK (again, BT.601).
It is bad, since matrix is derived from primaries, but all JPEGs are like
that. What can I say.
>An sRGB image, encoded at full range using BT.709 primaries should decode
to a perfect 1:1 regarding RGB values
It cannot be encoded not with BT.709 primaries, sRGB uses only BT.709
primaries. And no. Reference EOTF for SDR video is different from sRGB, so
they will not really decode 1:1.
>editor, the top row should result in RGB values as follows:
That is limited RGB. All color pickers use full RGB. See
https://en.wikipedia.org/wiki/SMPTE_color_bars
>There appears to be breakage with regard to the application of the
coefficients, as well as possibly misinterpretation of the full range
settings.
No there is not. It is just you that did tag the output files and it
decodes using BT.601. See https://res18h39.netlify.app/color
Use yellow limited range: 180 180 16, after encoding using BT.709 matrix
and rounding is 168, 44, 136 which if you are decoding back with BT.601
will be 179, 191, 22, and here it is! FFmpeg thus is perfect and case
closed.
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Ticket URL: <https://trac.ffmpeg.org/ticket/3785#comment:19>
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