default snd-usb-audio alsa buffer too low (causes pops and clicks)

[Wit Wilinski]

Default sound buffer set by ALSA for USB soundcards (in my case 0d8c:0006 C-Media Electronics, Inc. with CM-106 chipset, usb-audio driver,
/proc/asound/cards says:
 0 [Audio ]: USB-Audio - USB Audio
                      USB Audio at usb-0000:00:1d.0-2, full speed
) is too low for ordinary, 2-channel playback. Sound skips from time to time regardless of the system load and I/O usage. Seems the latency of PCI/USB bus is higher than the default buffer size set by ALSA. The configuration which resolves the problem looks like this (/etc/asound.conf):

defaults.ctl.card 0
defaults.pcm.card 0

pcm.card0 {
  type hw
  card 0
}

pcm.dmixer {
  type dmix
  ipc_key 1025
  slave {
    pcm "hw:0,0"
    period_time 0
    period_size 2048
    buffer_size 32768
    rate 48000
  }
  bindings {
    0 0
    1 1
  }
}
pcm.skype {
  type asym

  playback.pcm "dmixer"
  capture.pcm "card0"
}

pcm.!default {
  type plug
  slave.pcm "skype"
}

The buffer_size used here might be too large, but I haven't encountered any problems since using that configuration.