Problem with snd_ich and vchans

Michael Nottebrock michaelnottebrock at
Wed Dec 10 13:21:09 PST 2003

This is probably a known phenomenon, but I report it anyway since I'm not sure 
it is known for this specific combination.

I have a mobo with onboard sound:

pcm0: <Intel ICH2 (82801BA)> port 0xe800-0xe83f,0xec00-0xecff irq 10 at device 
31.5 on pci0
pcm0: <C-Media Electronics CMI9739 AC97 Codec>

running by default with hw.snd.pcm0.ac97rate: 48000.

Now when I enable vchans, sound plays back to slowly (pitched down), fiddling 
with above sysctl doesn't have any effect. I found the following in vchan.c:

        /* XXX gross ugly hack, kill murder death */
        if (first && !err) {
                err = chn_reset(parent, AFMT_STEREO | AFMT_S16_LE);
                if (err)
                        printf("chn_reset: %d\n", err);
                err = chn_setspeed(parent, 44100);
                if (err)
                        printf("chn_setspeed: %d\n", err);

When I change the 44100 to 48000 there, sound plays back normally with vchans 

   ,_,   | Michael Nottebrock               | lofi at
 (/^ ^\) | FreeBSD - The Power to Serve     |
   \u/   | K Desktop Environment on FreeBSD |
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