ffmpeg generates mono ALAC .m4a sound files which play double speed in totem (but play fine with ffplay and alac-decoder)
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
libav (Ubuntu) |
Confirmed
|
Low
|
Unassigned |
Bug Description
(description edited)
ALAC (Apple Lossless Audeo Codec) sound files created with "ffmpeg -acodec alac" play
at double speed using totem, if the original input .wav file was monophonic.
The problem does not occur with stereo files.
The resulting mono .m4a file plays wrong on an iPOD classic, and on Linux using totem.
The same mono .m4a decodes on linux using alac-decoder to produce a *stereo* .wav file which plays at normal speed (I'm guessing that whatever the problem is with the mono ALAC .m4a file is "fixed" by duplicating the mono track).
Since the iPOD matches totem's behavior, it is extremely likely that ffmpeg needs to be changed to generate mono ALAC files which play correctly (OTOH, Apple might have a bug in its decoders with mono files).
Note: ALAC is not documented by Apple, so the only standards are Apple's close-source implementations.
I will attach a second demo archive. This time there are two small .wav files, one stereo and the other mono. The mono file was created from the stereo file using Audacity's Tracks->Stereo Track to Mono feature.
ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: libgstreamer0.10-0 0.10.30-1build2
ProcVersionSign
Uname: Linux 2.6.35-22-generic x86_64
Architecture: amd64
Date: Sat Oct 16 14:48:38 2010
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release Candidate amd64 (20100928)
ProcEnviron:
PATH=(custom, user)
LANG=en_US.utf8
SHELL=/bin/bash
SourcePackage: gstreamer0.10
affects: | gstreamer0.10 (Ubuntu) → ffmpeg (Ubuntu) |
Changed in ffmpeg (Ubuntu): | |
status: | New → Confirmed |
summary: |
- ffmpeg generates mono ALAC .m4a sound files which play double speed + ffmpeg generates mono ALAC .m4a sound files which play double speed in + totem (but play fine with ffplay and alac-decoder) |
affects: | ffmpeg (Ubuntu) → libav (Ubuntu) |
Changed in libav (Ubuntu): | |
importance: | Undecided → Low |
ALAC output from FFmpeg SVN-r25628 on Maverick is also distorted in Maverick's Totem. Totem 2.32.0/ gstreamer0. 10-ffmpeg 0.10.10 in Arch Linux x86_64 also has distorted decoding from the same output. FFplay from Maverick repo and FFplay SVN decode the file properly.
Consider reporting it upstream to FFmpeg (although they may blame totem, gstreamer, and/or iPod).