Bug#736088: libavcodec54: file command reports wrong bitrate on mp3 file encoded by libav

[Reinhard Tartler]

tags 736088 +upstream
stop

On Fri, Mar 07, 2014 at 12:04:25PM +0100, Alessandro Ghedini wrote:
> So, I've done a bit of investigation, and it turns out that this is caused by
> the way libavformat writes the XING header to mp3 files. Essentially, it uses
> a fixed value for bitrate_idx... for any bitrate values.
> 
> This also makes tools like mediainfo detect an avconv-encoded mp3 file as
> using constant bitrate, while in fact it might be using a variable bitrate
> (though I'm not sure if this is actually the same bug, or a different bug in the
> same code).
> 
> More or less copy-pasting the mp3_write_xing() function (libavformat/mp3enc.c)
> from ffmpeg to libav seems to fix the problem.

Could you please provide a patch, and send (or copy) it to libav-devel at libav.org, please?

Thanks.