[FFmpeg-devel] [PATCH] avformat/concat: fix missing metadata

[Andreas Rheinhardt]

Nicolas George:
> Steven Hartland (12022-07-02):
>> I'm using concat to join multiple files from a GoPro camera including the
>> three metadata streams, with the early return it fails as the metadata
>> stream information is missing so map fails.
> 
>> I believe the reason for the failure is that this early return prevents the
>> metadata from being preserved.
> 
> You are trying to trick concat into merging files with different streams
> and match streams between them. It is not how concat is designed to
> work, it might work in your particular test case but will not work in
> more complex cases and will break other use cases.
> 
> For example, with your change, if you concatenate a file with metadata
> "start_time=12:00" and another with "start_time=12:01", it will generate
> a file with both metadata entries instead of just the first one as would
> be desirable.
> 

Actually, the newer entry will overwrite the older entry; if you want
multiple keys with the same value, you have to use the AV_DICT_MULTIKEY
flag.

- Andreas