[MEncoder-users] How to get ".mp3" audio rather than "mp4a" audio?

[Sheppard, Mark]

On 16 November 2010 19:58 Reimar Döffinger wrote:
> On Tue, Nov 16, 2010 at 11:12:28AM +0000, Sheppard, Mark wrote:
> > mencoder 588.wmv -o 588.mp4 -oac mp3lame -lameopts cbr:br=128 -
> channels 2 -srate 44100 -ofps 25 -of lavf -ovc x264 -x264encopts
> bitrate=1500:subq=5:8x8dct:frameref=2:threads=auto:global_header:nocaba
> c:nob_adapt:bframes=0:keyint=50 -lavfopts format=mp4 -vf
> harddup,scale=1280:720
> 
> I can't see any way that would result in a video with mp4a audio.
> I don't have an mencoder with lame/x264, but
> -ovc lavc -oac lavc -of lavf -lavfopts format=mp4
> for me results in a file with mp2 audio.

The output of the mp4info utility (from http://packages.ubuntu.com/lucid/mpeg4ip-utils) shows the following information for a file that works (i.e. produced before the upgrade):

Track   Type    Info
1       video   H264 High at 3.1, 223.720 secs, 1446 kbps, 1280x720 @ 25.000000 fps
2       audio   .mp3, 223.921 secs, 128 kbps, 44100 Hz

And this for a file that doesn't work (i.e. produced after the upgrade):

Track   Type    Info
1       video   H264 High at 3.1, 201.680 secs, 1422 kbps, 1280x720 @ 25.000000 fps
2       audio   MPEG-1 Audio (11172-3), 200.359 secs, 0 kbps, 44100 Hz
 Tool: Lavf52.64.2

So my guess is that the "mp4a" bit reported by mp4dump is some extra/diiferent chunk description thing, but the audio is still in MP3 format, which is officially called "MPEG-1 Audio (11172-3)".  It's just that the flash player doesn't understand that and needs the old behaviour of having a file which has a ".mp3" chunk/header/tag/whatever.  Which is why I tried adding the " -fafmttag 0x55" option mentioned in the mencoder man page.  But that didn't help.

I'm not totally au fait with all the video, audio and container formats and codecs so could well have the wrong end of the stick on this!

Cheers,
Mark.