On Mon, Dec 11, 2017 at 10:58:41PM +0100, Paul B Mahol wrote:
> On 12/11/17, Michael Niedermayer <mich...@niedermayer.cc> wrote:
> > On Mon, Dec 11, 2017 at 12:09:33PM -0500, Vittorio Giovara wrote:
> >> >* On 12/8/17, Paul B Mahol <onemda at gmail.com <http://gmail.com>>*
> >> >> On 12/8/17, Vittorio Giovara <vittorio.giovara at gmail.com
> >> >> <http://ffmpeg.org/mailman/listinfo/ffmpeg-devel>> wrote:
> >> >*> If we were to break this feature, I'd suggest going the full route of
> >> *>*> adding a PixelFormaton and work on a sws alternative (one is allowed
> >> to
> >> *>*> dream no?).
> >> *>
> >> > This is step to right direction, why would adding yet another API be
> >> > better
> >> > solution?
> >> >
> >> > J formats are hack - misfeature - most obvious reason why nobody added
> >> > 10bit J formats, or one of alpha. Calling it otherwise, points to
> >> > severe
> >> > lack of understanding of problem.
> >>
> >> I am perfectly aware that the J formats are a hack, that's why it would
> >> be
> >> nice to avoid introducing more hacks to get rid of them.
> >> As it has been pointed out in the other thread, simply adding
> >> .color_range
> >> does not properly solve this problem, it is a breaking change without
> >> proper deprecation period, and in general it seems like not a good idea
> >> API-wise to add an endless number of fields to AVCodec.
> >> Like I said, having dealt with the problem in the past, the only way I
> >> suggest to go forward is decoupling codec/filter negotiation from pixel
> >> formats and use a different scaling/color conversion library.
> >
> > The problem is completely unrelated to the scaling/color conversion
> > library. Its difficult to remove them from libavcodec and libavfilter.
> > And i belive paul is doing good and hard work here.
> >
> > If there is a issue in swscale from spliting range out, iam happy to
> > look into fixing that if someone gives me a reproduceable test case
> >
> > thx
> Just create separate pixel format for every color range, bitdepth,
> colorspace, etc combination.
> Or you want pixel formats as objects?

> struct AVPixelFormatHax {
>     enum ColorMissingSpace color_space;
>     enum ColorFillRange color_range;
>     enum ColorPrimus  color_primaries;
>     int  nb_components;
>     int *bitdepths;
>     int  nb_planes;
>     Copy big pixdesc struct and add more stuff here... (Can this be
> done in pure C?)
> }

If you go for a struct, spliting this in 2 parts
the first being the physical layout of the samples
(plane numbers, depth packing variant)
and the 2nd being the logical
that is what the samples actually represent (colorspace, range, ...)
might make sense

struct AVPixelSoup {
    enum AVPixelFormat pix_fmt; // This describes the physical layout
    struct ColorWhateverDescriptor color_descriptor; // this described the 
logical content

struct ColorWhateverDescriptor{
    enum ColorMissingSpace color_space;
    enum ColorFillRange color_range;
    enum ColorPrimus  color_primaries;

Some advantages of this are
pixel_formats as they are currently largly stay (YUVJ goes,
planar RGB might be merged with planar YUV or may be left if its more 
practical, RGB might be merged with BGR or left)

because pixel formats largly stay as they are alot of code and API
related to it should not need to be changed.

Code that cares just about physical layout (copy, crop, ...) can just
work with the pixel_formats as it always did

about putting everything in a single (large) enum, i wonder how
large that would become
But a struct similarly could be a problem here if we have lists of all
supported variants that litterally contain an element for each specific

As far as iam concerned iam really happy with any API/implementation
that works and is practical(maintainable / has someone wanting to
implement it / ...)
The current code has quite a few shortcommings as it cannot
properly list or negotiate the support for colorspaces and others.

Iam not sure i should mention it or not as it might confuse but its
if one takes a step back from this and looks, the issue goes beyond pixel 
codecs can support some pixel formats in specific profiles only
or with specific resolutions only.
At that level merging things in a ever growing struct is not possible
anymore and different solutions would need to be found
I wrote av_opt_query_ranges / AVOptionRanges to allow "introspection"
of such information from any object that supports AVOptions.
But this system was AFAIK largly ignored by people
Of course its also solving a different problem than YUVJ removial here.
But maybe it or a similar system could be usefull for more complex
cases where a encoder or filter wants to convey to the user app what
ranges of fields it supports together with the already set elements.

> Now you feed this pile of items to each function in lib*
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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