[FFmpeg-devel] [RFC} extend pixdesc ?

Mark Himsley mark at mdsh.com
Sun Mar 20 12:16:27 CET 2011

On 20/03/2011 00:07, Stefano Sabatini wrote:
> On date Saturday 2011-03-19 19:41:07 +0000, Mark Himsley encoded:
>> Dear Developers,
>> It was previously noted in the thread "[FFmpeg-devel] libavfilter:
>> extending overlay filter" that each filter is doing its own
>> investigation to discover the layout of RBGA style formats, to discover
>> if the format has alpha, to discover the level of black.
>> Would it be appropriate to extend AVPixFmtDescriptor to contain a new
>> struct holding that information, and add that information to
>> av_pix_fmt_descriptors in pixdesc.c?
> This idea pops up from time to time. The problem is that the pixel
> format, and consequently the pixel descriptor, should only express the
> layout of the pixel components, while chroma and colorspace
> information should be placed somewhere else.
> Unfortunately until we properly implement this, we need to rely on
> various hacks for determining chroma/colorspace information from the
> pixel format, but we are trying to avoid to pollute the pixdesc struct
> with information which semantically doesn't belong there.
> But I agree in the meaningwhile we may rely at least on shared
> internal routines for extracting this information from the pixel
> format enums.

Ok. Thanks, that's a very clear explanation.


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