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

[Leo Izen]

On 12/8/24 2:23 PM, Jan Ekström 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?
> 
> Jan
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Chunk name is included in the crc32 calculation, so if you see exactly 
four bytes change that is probably what you are seeing.

- Leo Izen (Traneptora)