[MPlayer-advusers] mp3 decoding problem (also libavformat issues)

[compn]

On Tue, 22 Nov 2005 22:56:01 -0500
The Wanderer <inverseparadox at comcast.net> wrote:

> compn wrote:
> 
> > On Wed, 26 Oct 2005 14:51:14 -0400
> > The Wanderer <inverseparadox at comcast.net> wrote:
> > 
> >> The Wanderer wrote:
> >> 
> >>> compn wrote:
> >>> 
> >>>> decoding this file causes audio glitches in mplayer
> >>>> -demuxer 35, -ac ffmp3, -dumpaudio, nothing helps
> >>>> user reports it playing fine in xine.
> > 
> > this is incorrect, i found if you combine such commandlines, you can
> > play the audio correctly in mplayer, i figured this out by studying
> > how vlc would do it
> > 
> > mplayer 163.mp4 -demuxer 35 -ac +ffmp3
> > 
> > but i'm told that the video speeds up/plays incorrectly
> 
> It does; if you also specify '-fps 24000/1001' it will play back
> perfectly. I've seen this discussed on the forums of the people who
> released the files, and hadn't reached the point of thinking to post it
> here.
> 
> > at least this gives you correct audio. altho i'm at a loss at why
> > ffmp3 is not handling mp3 audio when demuxed with lavf... old
> > codecs.conf or missing entry?
> 
> For one thing, the audio in the file is misdetected by FFmpeg - it
> thinks that it's AAC for some reason. (Probably to do with the fact that

i think i've narrowed down the bugs, maybe they are correct, maybe i'm 100%
wrong :)

bug #1 in mp3 in mp4 with -demuxer 35 is libavformat
using fourcc instead of the mpeg4 elementary stream descriptor atom
to pick which audio codec to use.

does mplayer use the elementary stream descriptor atom? i think yes?
does ffmpeg need to use this instead of fourcc?

AAC:
MOV track #0: 105 chunks, 948 samples
Audio bits: 16  chans: 2  rate: 44100
MOV: Found MPEG4 audio Elementary Stream Descriptor atom (51)!
Fourcc: mp4a

MP3:
MOV track #1: 2886 chunks, 0 samples
Audio bits: 16  chans: 2  rate: 48000
MOV: Found MPEG4 audio Elementary Stream Descriptor atom (35)!
Fourcc: mp4a


bug #2 is mplayer's mp4 demuxer is not demuxing the mp3 audio like
libavformat.


bug #3 is libavformat demuxing the framerate improperly
can someone verify this using ffplay on the same sample?

are there more bugs? is my bug list wrong?

-compn