On Wed, Nov 11, 2020 at 12:18:02AM +0000, Brian Matherly wrote:
> > > Am I (at all) on the right track here?:
> > >
> > > Yes!
> > >
> > > This code seems to say the avformat producer supports rgba, rgb24, and
> > > yuv422p?
> > > https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.c#L614-L630
> > >
> > > This is a better place to look:
> > > https://github.com/mltframework/mlt/blob/master/src/modules/avformat/producer_avformat.c#L1167rgba,
> > > rgb24, yuv420p, yuyv422
> >
> > Got it, thanks! So AVPixelFormat is the ffmpeg(?) pixel format, and
> > mlt_image_format is the type actually used by MLT services (or, at least,
> > by filters and transitions)?
>
> Yes.
>
> > The definition of mlt_image_format
> >(https://github.com/mltframework/mlt/blob/master/src/framework/mlt_types.h#L45-L58)
> > seems to have only mlt_image_yuv422p16 as a candidate capable of supporting
> >10-bit color; is > that right? All the rest (excluding glsl which I haven't
> >explored) seem to only be 8-bit?
>
> Yes.
>
> > And also is my math right that it is in fact able to support 10(+) bits of
> >color? - i.e. 2 chroma-subsampled pixels have (32 bpp*2==64) bits of color
> >information, divided by 4 (2 Y + 1 Cr + 1 Cb) == 16 bits per component?
> > A simpler way of saying this might be: the ffmpeg naming scheme for e.g.
> >"yuv422p10le" is the same as MLT's naming scheme for "yuv422p16", thus since
> >16 is greater than 10, we can definitely losslessly use 10-bit > colors (in
> >services that support 16-bit colors)?
> No. yuv422p16 is 16 bits per sample (32bits per pixel) because we prefer to
> operate on byte boundaries in MLT. It maps to AV_PIX_FMT_YUV422P16LE.
> https://github.com/mltframework/mlt/blob/master/src/modules/avformat/consumer_avformat.c#L591
>
Thanks, all of this has been really helpful!
Would adding 10-bit color support to the avformat producer "just" mainly
involve adding code like the below to producer_avformat.c, or is there a lot
more to it?:
----------
Adding cases to the switch statement in `pick_pix_fmt`:
case AV_PIX_FMT_YUV420P16LE:
case AV_PIX_FMT_YUV422P16LE:
case AV_PIX_FMT_YUV420P10LE:
case AV_PIX_FMT_YUV422P10LE:
return AV_PIX_FMT_YUV422P16LE;
----------
Adding cases to `pick_image_format`:
case AV_PIX_FMT_YUV420P16LE:
case AV_PIX_FMT_YUV422P16LE:
case AV_PIX_FMT_YUV420P10LE:
case AV_PIX_FMT_YUV422P10LE:
return mlt_image_yuv422p16;
----------
Adding a case to `convert_image`
----------
Thanks again,
Tom
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