[MPlayer-users] Trouble with Mp3 audio in MP4 containers

[The Wanderer]

On 12/20/2005 01:16 PM, WireSpot wrote:

> On 12/20/05, The Wanderer <inverseparadox at comcast.net> wrote:
> 
>> The internal MPlayer demuxer for MP4 files has some holes in its 
>> understanding of what constitutes an audio stream. Use '-demuxer
>> 35' to tell MPlayer to use the libavformat demuxer, and the audio
>> should play back fine.
>> 
>> The only MP4 files I have for which I need to use that option also
>> have a somewhat unusual internal label for the audio stream, such
>> that libavformat will not detect it as MP3; for those files, I have
>> to also specify '-ac +ffmp3'.
>> 
>> The libavformat demuxer also appears to have a mistaken idea of
>> what frame rate the files I have should be played back at; it plays
>> them at 30000/1001, which is much too fast. Specifying '-fps
>> 24000/1001' fixes the problem, without introducing any new ones.
> 
> Bah, I had to use all three:
> -ac +ffmp3 -demuxer 35 -fps 24000/1001

Yes, I did say "also" in reference to the second. For that matter, since
both the second and the third problems don't appear unless the
libavformat demuxer is used, I thought it would be obvious enough that
they would apply only when the first option was in effect.

> And the A/V was still off so I had to tweak it some more.

Hmm. That I haven't encountered; the playback is perfect for me once I
supply those three options. Off in what way, exactly?

> FWIW, in case anyone else runs into this problem, here's the
> workaround: remux to MKV with mpeg4ip 1.4 and mkvtoolnix 1.6.5.
> 
> Extract the audio from the MP4 file with mp4creator (from mpeg4ip),
> since mkvmerge (from mkvtoolnix) complains about garbage in the audio
> track. Then use mkvmerge to merge the video from the original file
> with the separate mp3 file. You get a working MKV instantly.

The "garbage in the audio track" may or may not be a result of the same
reason you have to specify -ac +ffmp3 - the audio stream is not labeled
with the usual MP3 identifier code.

> Since this is apparently a known problem with MPlayer, should I keep
> trying to upload my sample file? If the answer is yes, can anyone
> tell me why I can't write to incoming/ ?

You probably don't need to keep trying to upload, no.

The reason why you can't write to incoming/ is that, unless there's been
news I haven't heard, the main MPHQ server is still down. That's been
the case for quite some while, and there is some progress towards
getting the new one(s?) up and running properly, but I have no idea when
it's likely to happen.

-- 
       The Wanderer

Warning: Simply because I argue an issue does not mean I agree with any
side of it.

Secrecy is the beginning of tyranny.