Noise when playing mp3 file with only one channel using jack soundserver.

Submitted by 1984 on Wed, 2013-09-18 13:26

Forums:

Hi,

=== System ===

* Arch Linux fully updated
* Music On Console (version 2.5.0-beta1, revision 2506) from the Arch Repos

=== Bug ===

When playing an mp3 file with only one channel while using JACK as the soundserver (with ALSA everything works) I get a very loud noise on the second channel. With stereo files everything is fine.

=== My analysis so far ===

Playing the same file with mplayer and ffmpeg or mpg123 the problem doesn't occur. So I think it's not related to the codecs.

Mplayer opens only one channel in the 'Jack Audio Connection Kit' while moc opens two. One of the moc channels is the noise while the other one normally plays the file. As the two channels of MOC in JACK are permanent I think the signal should be splitted.

The Mono option of moc doesn't change anything.

Interestingly ogg files work. It seems that the decoder automatically splits the one-channeled signal and maps it on two channels. The output also runs over two channels and not one as with mp3 files.

=== Any questions? ===

Ask. :)

Best,
1984

jcf

Wed, 2013-09-18 21:42

Can you turn on logging (the -D option) and start playing an errant MP3. As soon as it starts playing, stop and quit MOC then compress and send mocmaint the mocp_server_log file.

1984

Wed, 2013-09-18 23:45

I sent you the file.

jcf

Thu, 2013-09-19 00:31

Thanks. I've now reproduced the problem on the current SVN HEAD with ALSA.

jcf

Fri, 2013-09-20 23:29

Patch committed to SVN as r2555.