[MPlayer-advusers] mp3 decoding problem (also libavformat issues)
compn
tempn at twmi.rr.com
Fri Nov 25 20:08:39 CET 2005
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
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