[FFmpeg-devel] [PATCH v3] lavc/aomdec: Allow RGB decoding

Thilo Borgmann thilo.borgmann at mail.de
Thu Jun 10 23:28:46 EEST 2021


Am 10.06.21 um 20:26 schrieb Balling:
> чт, 10 июн. 2021 г., 20:33 James Zern <jzern at google.com>:
> 
>> On Thu, Jun 10, 2021 at 9:26 AM Валерий Заподовников
>> <val.zapod.vz at gmail.com> wrote:
>>>
>>>> This doesn't match the check in libdav1d.c.
>>>
>>> I do not really care what libdav1d.c does, since it uses internal to AV1
>> spec DAV1D_MC_IDENTITY (and frame->colorspace). This should have been a no
>> go into FFmpeg, but it was not somehow. FFmpeg can handle all of this in by
>> itself, there is no need to use examples from AV1 spec, which are wrong by
>> omission: see for yourself.
>> https://github.com/FFmpeg/FFmpeg/blob/c8778606b3811da6bd58ca6b73d2446bd430013e/libavcodec/libdav1d.c#L299
>>>
>>
>> It would be better to put this on the list for others to be able to
>> comment on.
>>
>>> This is sRGB definition from AV1, not R'G'B' (or even RGB in case of
>> linear transfer) and thus is total garbage. What if the file is tagged with
>> DCI-P3 transfer and/or primaries? I am not going to fix libdav1d.c, since
>> as I said, it uses internal names and internal deliberations which are
>> unacceptable.
>>>
>>> Again. AV1 spec is really quite hillarious in that part. For example it
>> does mention XYZ, but does not check for it anywhere, try Ctrl-F here:
>> https://aomediacodec.github.io/av1-spec/av1-spec.pdf
>>>
>>> Thus I did implement filtering this out too, since FFmpeg does support
>> XYZ pixel format (and maybe somebody one day will implement it too).
>>>
>>> Listen, my patch is correct. AV1 spec is also telling the same, as it
>> shows all the possible primaries and transfers. But it only looks into sRGB
>> scenario, since your people (Google, etc) were not capable to implement
>> normal icc color management, but FFmpeg with mpv can do it and thus no need
>> to concentrate on sRGB like your people did. I mean you can fix AV1 spec if
>> you want, but IMHO it is correct already, this is color spaces info 101 and
>> AV1 is depending on ITU-R H.273.
>>
> 
> 
> Okay, I will put it into the mailing list.


> P.S. Dunno what that guy was thinking. I am not going to inline my comments
> any more than I want to. I mean sure I do not top post, but just since this
> is just waste of Internet traffic, and so is inlining in most cases (but
> right here it is COOL and very needed).


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-Thilo

[1] https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2021-June/281206.html
 



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