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

[Philip Langdale]

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On Wed, 21 Feb 2018 23:37:57 +0100
Nicolas George <george at nsup.org> wrote:

> Philip Langdale (2018-02-21):
> > As part of achieving our YUVJ-free future, it needs to be possible
> > to pass the colour range property from a decoder context to an
> > encoder context. In the absence of filters, this is obviously
> > trivial, but as soon as filters are introduced, there needs to
> > be a way to pass and preserve the property (or modify it, as
> > some filters will do).
> > 
> > Based on existing properties of this type, this change adds a
> > link property and ways to set it from a buffer source and get it
> > from a buffer sink.  
> 
> I am not sure when I will be able to give a close look at the code,
> so I make my general comment immediately:
> 
> Are you sure this is a property that must be forwarded and not
> negotiated?
> 
> You seem to say that encoders may support a limited set of ranges. It
> looks like the range should be constrained by the output, like the
> pixel format, and negotiated on the chain to insert a conversion
> filter if necessary.
> 
> But I am not familiar with color ranges. I just want to make sure you
> have considered the question.
> 
> Regards,
> 

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.

- --phil
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