>>A high-end audio company has asked me to get their newly released USB
>>DAC working in Linux at 24-bit. 16-bit playback is said to be
>>working. I'm hoping I only need to use a 24-bit music player like
>>mpd, but if that doesn't work, where should I look next? Can a DAC
>>work in Linux at 16-bit but not at 24-bit?
>>
>>- Grant
>
> Two stages-
> First test the card from aplay to make sure it does work at 24 bits, with 24
> bit files. If it does then you need the latest version of MPD to get 24 bit
> audio support (0.15. alpha). I have been working on a host pc solution to
> specifically support HD audio playback, and was responsible for getting the
> MPD team the necessary info to get 24 bit playback working. It does support
> through 192/24 correctly. The remaining issue is seeking on wave files.
>
> I have not been able to get the other audio programs to work as cleanly.
>
>
> Demian
Hi Demian,
I've got the USB DAC working up to its max of 24/96 with mpd. I had
to specify oss instead of alsa in mpd to get it to go above 48k.
Maybe dmix was getting in the way.
The only problem is the sound has a lot of static in apps other than
mpd like miro and mplayer. I noticed there are other audible problems
when the DAC is fed 48k in mpd. I don't think it upsamples well
internally. So, I tried to lock dmix to 24/96 with an .asoundrc I
found online. The result is the 96k LED is illuminated on the DAC,
but the static remains. Please let me know if you have any ideas on
eliminating this static which exists in apps other than mpd. Here is
my .asoundrc:
pcm.usb-audio {
type hw
card 0
}
pcm.!default {
type plug
slave.pcm "dmixer"
}
pcm.dmixer {
type dmix
ipc_key 1024
slave {
pcm "hw:0,0"
format S24_3LE
period_time 0
period_size 1024
buffer_size 8192
rate 96000
}
bindings {
0 0
1 1
}
}
ctl.dmixer {
type hw
card 0
device 0
}
pcm.dsp {
type plug
slave.pcm "dmixer" # use our new PCM here
}
ctl.mixer {
type hw
card 0
}
- Grant
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