Sounds breaks up with 5.2-STABLE

Andrew Kilpatrick andrew at
Mon May 24 13:17:02 PDT 2004


I'm using FreeBSD 5.2-STABLE on my workstation and have just installed
a CMedia CMI8738-based sound card. The card has worked well under
OpenBSD in the past (even 3 in the same machine!) but with FreeBSD
the sound breaks up and is choppy if I do specific things in X like:

- opening new windows
- dragging a window
- scrolling in my browser
- holding down a key (like space)

It sounds like the buffers are underrunning. Looking at /dev/sndstat with
verbose set to 3 reveals a lot of buffer underruns, but it doesn't seem to
notice them all. I've tried unsuccessfully setting the hw.snd.pcm0.buffersize
variable higher than 16384, but to no avail.

My system is a Mini-ITX EPIA 533MHz board with a CMI8738-based
card. Top shows lots of CPU idling. I wrote a little program in C to open
the sound card and dump stdin to it, so I can see how fast it's consuming
buffers and fiddle with the ioctls and stuff, but nothing I do seems to make
it work, and writing buffers larger than 16384 makes it play with gaps
between buffers.

That's what I've tried so far... any help would be greatly appreciated!



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