[FFmpeg-devel] [PATCH 1/3] avfilter: Add support for colour range as a link parameter

[Paul B Mahol]

On 7/25/18, Kieran O Leary <kieran.o.leary at gmail.com> wrote:
> Hi,
>
> On Thu, Feb 22, 2018 at 4:15 PM, Philip Langdale <philipl at overt.org> wrote:
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>>
>> On Thu, 22 Feb 2018 12:39:16 +0100
>> Nicolas George <george at nsup.org> wrote:
>>
>>> Philip Langdale (2018-02-21):
>>> > Negotiation is part of Paul's larger changeset, and will be a useful
>>> > feature. My change is still a strict improvement over the current
>>> > state of the world - where range is not propagated at all,
>>> > regardless of compatibility. In those situations where negotiation
>>> > is required, the status quo will essentially continue, with the
>>> > range value not accurately reflecting the frame contents.
>>>
>>> I am not comfortable with what you write here.
>>>
>>> I am afraid that adding negotiation on top of this would be more work
>>> than adding negotiation on top of the current code.
>>>
>>> I am also afraid that an incorrect value is worse than an unspecified
>>> one.
>>>
>>> But it all depends on what filters and codecs actually do with the
>>> color range, and that I do not know.
>>>
>>> Could you perhaps make a little summary of that issue: where the color
>>> range comes from, which filters and encoders do not care, which ones
>>> only work with one, which ones do something special with it? Maybe as
>>> a longer doxy comment for enum AVColorRange in libavutil/pixfmt.h?
>>
>> You can go back and read through Paul's patchset from december, which
>> implements negotiation. My changes here are a strict subset of those,
>> so empirically, merging this subset on its own does not make
>> negotiation harder. You are also welcome to recommend merging his full
>> patchset now; it never got the reviews it needed, but that doesn't mean
>> it can't.
>>
>
> I am hoping to test out this patchset in the hopes that it could
> rectify the issue we're having with colour metadata in a MOV/ProRes
> file not being migrated over to Matroska:
> https://ffmpeg.org/pipermail/ffmpeg-user/2018-July/040717.html
>
> I have two questions as I'm a bit confused:
> 1. Does this patchset require Paul's patchset to be merged? I can't
> tell if it has already or not.
> 2. I see that this thread describes a series of 4 patches, but there
> also seems to be
> a set of three patches from February - do the set of 3 supercede this
> set of 4? https://patchwork.ffmpeg.org/patch/7694/
>

IIRC this patchset have been applied, you have color range in lavfi filtergraph.
But it is not used for negotiation....

Also this patchset only plays with color range and other properties
are not touched.