USB sound card crackling when changing nr of channels in ALSA

Question

Hello! I have read the alsa config and some related posts from brebs (https://bbs.archlinux.org/profile.php?id=10353) and I setup upmixing to 5.1 and dmix with a USB sound card. It works, but the sound is constantly crackling. I have simplified my .asoundrc to find out where did this problem came from and I got this:
pcm.!default {
type plug
slave.pcm "dmix6"
pcm.dmix6 {
type asym
playback.pcm {
type dmix
ipc_key 567829
slave {
pcm "hw:0,0"
channels 6
It strill crackles with this config but when I change the channels to 2 there is no crackling anymore. I messed with buffer_size and period_size but the problem persists. Using surround51 does not fix it either. Thank you!
Edit: Forgot to mention my sound card, it's a Sweex SC016.
Last edited by Sergius (2014-04-10 03:30:52)

Answer 1

emeres wrote:Are there sound artefacts when using speaker-test -c 6 -D 'hw:0,0' ? What speed does that particular usb port have (what version)? What modules does this soundcard use?
I can't exactly tell if there are artifacts with that static sound but I think I the sound was clean. The output of lsusb -D /dev/bus/usb/004/002 has a line containing "bcd USB 1.10" and this is the output of "lsmod | grep '^snd' | column -t" (taken from the ALSA wiki):
snd_usb_audio 94732 0
snd_usbmidi_lib 16191 1 snd_usb_audio
snd_rawmidi 14796 1 snd_usbmidi_lib
snd_seq_device 4252 1 snd_rawmidi
snd_hda_codec_realtek 39245 1
snd_hda_intel 31703 0
snd_hda_codec 129306 2 snd_hda_codec_realtek,snd_hda_intel
snd_hwdep 4746 2 snd_usb_audio,snd_hda_codec
snd_pcm 64085 3 snd_usb_audio,snd_hda_codec,snd_hda_intel
snd_page_alloc 6134 2 snd_pcm,snd_hda_intel
snd_timer 14974 1 snd_pcm
snd 44446 10 snd_hda_codec_realtek,snd_usb_audio,snd_hwdep,snd_timer,snd_pcm,snd_rawmidi,snd_usbmidi_lib,snd_hda_codec,snd_hda_intel,snd_seq_device
I'm a newbie at Linux administration so I don't really know if this is what you need. Thank you!