[FFmpeg-devel] [PATCH] avcodec/png{dec, enc}: update mDCV and cLLI chunk capitalization

[Jan Ekström]

On Sun, Dec 8, 2024 at 9:23 PM Jan Ekström <jeebjp at gmail.com> wrote:
>
> On Sun, Dec 1, 2024 at 4:21 PM Leo Izen <leo.izen at gmail.com> wrote:
> >
> > The PNGv3 Specification Draft [1] has changed the capitalization
> > of mDCV and cLLI chunks (formerly mDCv and cLLi). This patch updates
> > FFmpeg to work with the new chunk names while retaining decode-side
> > compatibility with files created using the old names.
> >
> > [1]: https://w3c.github.io/png/
> >
>
> Code-wise LGTM. I'd like the semantic change to be mentioned in the
> commit message, so if you can add that when applying I'd be much
> obliged.
>
> BTW, I noticed that locally more bytes changed on
> tests/data/fate/png-mdcv.image2pipe than I would have expected when
> visualizing with vbindiff (not just the identifiers but some bytes
> following them, specifically the four bytes starting on the 9th byte
> after "cLLI" and from the 25th byte after "mDCV"). Is this also
> something you see or is this just my Fedora giving me grievances
> again?
>

Alright, according to responses on IRC it seems like these were block
checksums, so those additional differences are OK. TIL we wrote such.

Jan