[FFmpeg-devel] [PATCH v4] avcodec/pngdec: read colorspace info when decoding with AVDISCARD_ALL

[Ronald S. Bultje]

On Wed, Feb 22, 2023 at 8:49 AM Leo Izen <leo.izen at gmail.com> wrote:

> On 2/21/23 20:42, Ronald S. Bultje wrote:
> > Hi,
> >
> > On Tue, Feb 21, 2023 at 5:36 PM Leo Izen <leo.izen at gmail.com
> > <mailto:leo.izen at gmail.com>> wrote:
> >
> >     These chunks are lightweight and it's useful information to have when
> >     running ffmpeg -i or ffprobe, for example.
> >
> >
> > I disagree conceptually with this. If we want to skip "all" decoding, we
> > should also skip metadata for said frames.
> >
> > I think what we're looking for here is a partial decoding stage, e.g.
> > "header-only" or similar, instead of "including framedata", for some or
> > all frames. That's orthogonal to AVDISCARD_*.
> >
> > Ronald
>
> The issue is that libavformat and ffmpeg.c obtain metadata by calling
> the decoder with AVDISCARD_ALL. What you're proposing would require a
> structural change elsewhere, and I'm not sure it makes sense to block a
> patch like this one based on a hypothetical change elsewhere.


That’s fair. I’ll put this in the long term wishlist bucket.

Ronald