[FFmpeg-devel] Enhancing/extending OpenEXR 'gamma' feature

[Paul B Mahol]

On 8/28/15, Kevin Wheatley <kevin.j.wheatley at gmail.com> wrote:
> HI,
>
> I was wondering what others think about the option of extending the
> OpenEXR reader's gamma option to also include various transfer
> characteristic curves, potentially corresponding to the various
> AVCOL_TRC_* options, though I don't immediately have a need for all of
> them.
>
> In addition I could see the need for other curves like those of cinema
> camera vendor log curves, for instance Red, Sony, ARRI.
>
> From a user point of view I'd see a command line option specific to
> the EXR codec that would take a subset of the colour_trc options
> (bt709, etc) extended to include some camera transfer curves and it
> would apply the appropriate function prior to the encoding as
> AV_PIX_FMT_RGB48/64 as is done currently.
>
> I'm thinking the command line option would be called 'apply_trc'  or
> something similar.
>
> Why it is needed is simply that the gamma function isn't really
> sufficient for matching all the typical formats we see in production
> use.
>
> What would be nice would be to embed more colour adjustments prior to
> the truncation to integer values but that could be quite complex and
> may be better handled outside of ffmpeg.
>
> I've seen that there was a mention of something similar in the list
> archive, but could not find anything other than those emails.
>
> I'd be great full if any of the devs could comment on the idea before
> I start on the implementation.
>

Feel free to do it.

Note however that those various curves really belong to avfilter once
swscale supports float pixel format and exr decoder make use of it.

> Thanks
>
> Kevin
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