[Solved] Crackling audio from Syba C-media USB audio adapter

[permitivity]

EDIT: Found the solution. See second post.


A few weeks ago, I got a a Syba USB audio adapter and played around with using it as an airplay sink. It worked pretty good on the Pogoplug I had it on.

Today, I setup another (different) Pogoplug, installed Arch on it fresh. Plugged in the same Syba USB adapter. But when I play an mp3 file on it using mpg123, I get horrible crackling from the USB adapter line output.

I took the Syba adapter from the fresh Pogoplug and put it on the older pogoplug (the one I had airplay working on), play the same mp3 file using mpg123. No crackling.

Both are running the same version of Arch. I'm not sure what else I did on the older pogoplug installation to make the audio sound good. I kind of remember having crackling audio on it a few weeks ago when I was first playing with it, but somehow that got resolved. I tried installing airplay on the new pogoplug, just in case the programs I installed to get airplay somehow fixes the crackling issue, but no dice. And maybe I installed some other stuff back then, but I can't remember.

Anyways, anyone else run into this crackling issue? It seems to be software related.

Here's what I did, basically following Qui's guide for airplay.

$this->bbcode_second_pass_code('', '
pacman -Sy libao alsa-utils avahi libpulse
echo "use_mmap=no" >> /etc/libao.conf
')

EDIT: I just saw the note on the wiki about reducing latency to solve the crackling problem, but I don't have this file they are referring to:
https://wiki.archlinux.org/index.php/Ad ... SB_devices

$this->bbcode_second_pass_quote('', '
')/etc/modprobe.d/modprobe.conf

[permitivity]

Ok, I think I found out why. I think you need to edit the /etc/asound.conf with this. If you don't have a asound.conf file, just make one. Not sure which of those lines in the conf file solved the problem. I think it has to do with the "PCM" lines. This was copied from Qui's tutorial for airplay, so thanks to Qui.

http://blog.qnology.com/2013/03/tutoria ... linux.html

$this->bbcode_second_pass_code('', '
pcm.!default {
type plug
slave.pcm "softvol"
}
pcm.dmixer {
type dmix
ipc_key 1024
slave {
pcm "hw:0"
period_time 0
period_size 4096
buffer_size 131072
rate 41100
}
bindings {
0 0
1 1
}
}
pcm.dsnooper {
type dsnoop
ipc_key 1024
slave {
pcm "hw:0"
channels 2
period_time 0
period_size 4096
buffer_size 131072
rate 41100
}
bindings {
0 0
1 1
}
}
pcm.softvol {
type softvol
slave { pcm "dmixer" }
control {
name "Master"
card 0
}
}
ctl.!default {
type hw
card 0
}
ctl.softvol {
type hw
card 0
}
ctl.dmixer {
type hw
card 0
}
')