[FFmpeg-devel] [PATCH 2/3] avfiltergraph: don't query formats if filter has uninitialized inputs

Nicolas George nicolas.george at normalesup.org
Sat May 5 12:07:37 CEST 2012

Le quintidi 15 floréal, an CCXX, Michael Niedermayer a écrit :
> what disadvantage does it have if it supports any output and calls
> libswresample when it cannot otherwise produce it ?

The chances that lavfi will guess exactly the correct channel layout that
amerge wants to output, or even just the correct number of channels, are
very thin (unless the heuristics are specifically tuned for amerge, and that
has its own disadvantages), so the user would have to specify the output
format (using aformat) almost every time.

This is worse than now, where they have to specify the input format
only occasionally.

Also, it makes one more point where automatic conversion happens, and
therefore more difficult to control them. See "Using ‘-f lavfi’, audio
becomes mono for no apparent reason." in the FAQ for the drawbacks of
automatic conversions (this one is fixed now).

Furthermore, the same would be required of any future filter with similar
structure, that makes a lot of code duplication.


  Nicolas George
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20120505/346f37f9/attachment.asc>

More information about the ffmpeg-devel mailing list