[FFmpeg-devel] [PATCH] avcodec: Add AVClass to AVCodecParameters

Hendrik Leppkes h.leppkes at gmail.com
Tue May 10 15:56:18 CEST 2016

On Tue, May 10, 2016 at 2:10 PM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> libavformat gathers information about streams in av_find_stream_info()
> and that is all information completely unneeded by decoders
> no decoder needs the width and height from the parser run by
> av_find_stream_info() or other fields. These are only needed when they
> come from format headers.
> The only reason to go to the troubble to set these fields (and thats
> quite some troubble) is to provide this information to the user
> application and thus user

Technically the decoders wouldn't need this information, that is correct.
However, many applications do on a technical level. ffmpeg.c for
example would die a horrible death if it wouldn't know the resolution
of the video beforehand, because its setup requires this crucial
information before initializing filters and output encoders.

One could write an application to respond to such data on the fly, but
alas many apps at least want an initial value, or can't even respond
to dynamic changes at all.
Having this information available to the user to choose streams from
is nice, but not the only reason.

- Hendrik

More information about the ffmpeg-devel mailing list