[FFmpeg-devel] [PATCH] avformat/oggparseogm: sync avctx w/ codecpar

[Chris Cunningham]

On Fri, Feb 8, 2019 at 2:37 PM Michael Niedermayer <michaelni at gmx.at> wrote:

> ogg allows chaining streams when they have differing serial numbers
> https://xiph.org/ogg/doc/oggstream.html
>
> i think ive seen actual files doing this
>
> ogg_replace_stream() might assign these into existing avstreams i think
>

If I'm reading this correctly, I think that should always happen at the
boundary of a new ogg page, meaning it wouldn't rely on this multiple
headers logic?

I found the commit where this was introduced
https://github.com/FFmpeg/FFmpeg/commit/81b743eb1026547270b88ac6a5cb451a3907ee94?diff=split

With the description:
This fixes some old ogm files that had the 3rd vorbis header after a data
packet in another stream. This is invalid in ogg, but this change shouldn't
affect the behaviour of any valid file.

So, I don't think we're going to find spec text for this. No spec for OGM
and committer indicates its not valid Ogg. I'm guessing we want to still
support these ogm files?