[FFmpeg-devel] [PATCH] avformat/ac3dec: detect fairplay encryption

[Hendrik Leppkes]

On Wed, Mar 4, 2020 at 5:57 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>
> Am Mi., 4. März 2020 um 17:53 Uhr schrieb Sebastian Hubbard
> <sebh-at-google.com at ffmpeg.org>:
> >
> > I knew this was an ABI change and probably wasn't going to be
> > acceptable, but I decided to share it for consideration anyway.
> > There's special code in av_probe_input_format3 to skip over id3 tags
> > for the purposes of format detection, but Apple uses id3 tags to
> > signal information for HLS audio only tracks. Maybe this change
> > shouldn't be made, but if it could ever be helpful for another format
> > prober to know about leading id3 tags this is the only way I could
> > imagine it.
>
> If the additional fields are necessary (I don't know), they could be
> added to the end of the struct where they do not break abi.
>

Unfortunately, thats not true for every struct. In this case, for
example, they are being added at the end, but a caller could still
provide a smaller one  and we would try to read/write beyond the
provided struct.

- Hendrik