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Miscellaneous ALSA Patches

I got a new PowerMac G5 Quad a couple of weeks ago. Nice machine, except for the weak graphics and non-existent sound support on Linux.

The built-in sound card is completely unsupported at this time. As I did not feel like writing a driver for it, I plugged in an old USB sound device (Creative Sound Blaster Audigy 2 NX). At first this did not work, I just got oopses. But with a small fix (included in the kernel since it started to work.

Next I tried to set up ALSA‘s dmix plug-in with S16 which resulted in horrible crackling: The byte swapping code was broken.

Also, ALSA’s softvol plug-in (not strictly necessary but nice to have with GNOME’s volume control applet) didn’t work, it did not support any format available with snd-usb-audio on big-endian machines.

Here are the fixes for these two problems (against alsa-lib-1.0.11rc3):

If somebody is interested, here is the USB-Audio.conf I use with my Audigy 2 NX.

By the way: Is it normal that the dmix plug-in consumes 100% CPU?

April 9th, 2006: The patches have been integrated into alsa-libs 1.0.11rc4, the 100% CPU issue is fixed in that version too.
There’s also a ALSA driver for the chip in the PowerMac Quad now, see this mail from Johannes Berg.

This article Jürgen Kreileder is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.


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john smith said

That’s funny, I just turned my new Mac on and it worked. Everything worked fine. No problems at all… :)

Yes, most Mac sound cards are supported by Linux nowadays, the card in my old PowerMac 2.0 Dual (PowerMac7,2) works fine too but there’s no support for the card in the PowerMac11,2 yet.

Graphics card support is another story. The G5 Quad has an NVIDIA card, that means absolutely no 3D support.