The “white-noise” hiss seems to be a bug when using GPU acceleration for resampling. It depends on your USB video card. To fix mine, I created an asound.conf file that creates an audio device (so that OSMC doesn’t die if the USB DAC is turned off) and that explicitly disables resampling (I’m only using mine to run music).
My asound.conf is as follows:
pcm.Audio
{
type hw
card "Audio"
}
ctl.!default {
type hw
card "Audio"
}
pcm.!default {
type plug
slave {
#pcm "hw:1,0"
pcm "Audio"
rate "unchanged"
}
}
I got the info for this from Asoundrc - AlsaProject and Stop resampling! under Linux | Audiokarma Home Audio Stereo Discussion Forums (and a few more hints from http://openelec.tv/forum/124-raspberry-pi/74575-usb-dac-stopped-working-in-version-5-0 ) so that i could pass through bit-perfect music. I got the name of my device by running “cat /proc/asound/card1/id” because my USB DAC is the first card. “aplay -l” should give you any other info you need.
Once you’ve created the asound.conf file and rebooted, OSMC shows a new audio output device “ALSA Default…” and I selected that. Now my RPi with OSMC can be used to feed bit-perfect audio data to my hifi USB DAC.
Hopefully this is helpful to anyone with the same / a similar problem (hence adding my reference links).
Maz