FW: Audio drivers again?

Guenter Geiger guenter.geiger at psp-vie.be.philips.com
Thu Mar 25 10:55:45 CET 1999

The following was supposed to go to the list too.


> -----Original Message-----
> From: Miller Puckette [mailto:mpuckett at man104nfs.UCSD.EDU]
> Sent: Wednesday, March 24, 1999 6:29 PM
> To: pd-list at iem.mhsg.ac.at
> Subject: Audio drivers again?
> Hi list,
> I'm now running Pd under Red Hat Linux, and (like everybody else) I've
> run into some questions about audio/MIDI drivers.  Would
> anyone already know
> the answers to these?
> 1.  I've got an OplSa3 soundcard and so far I've been using
> the OSS drivers
> (the free ones from the RedHat 5.2 CDROM).  I notice that the
> ADC noise
> floor (measured in the test tone patch) is around 45 dB, whereas the
> SAME HARDWARE gets a noise floor of 20 dB under NT.  I've got a wild
> guess that this might be related to which of the two "DMA
> channels" I assign
> to "DMA0" and "DMA1"...  any other wild guesses out there?

Hmmm .. if it is not a problem of the mixer settings, I´d rather suspect
in the OplSa3 driver code. DMA0 and DMA1 are both 8 bit DMA´s and they shouldn´t
do anything else but transfer the data to the card.

So it could be any open mixer channel "mic in", "line in" or "CD in", or prob.
the relation
between "wave out" and "master out" channels.

Or something in the driver code.

Do you get reliable full duplex with this card ?
(Just asking cause I want to know which cards work)

> 2.  I also want to test the ALSA drivers.  I note in the ALSA
> FAQ (part
> of the release) that ALSA comes with an OSS compatibility package.  So
> is there any advantage to using the ALSA drivers "natively"
> (as s_alsa.s
> does) rather than just using s_linux.c and having ALSA
> emulate OSS audio?

ALSA´s OSS emulation simply doesn´t work in full duplex (on my system at least).
Seems it doesn´t like the small audio buffer settings.

Anyhow, I never understood why they really changed the API instead of expanding
in a compatible way and wrapping their ALSA library around it.

> 3.  Same question for MIDI...  is it likely to be worth the trouble of
> rewriting the MIDI I/O code to address ALSA natively?

Together with Wini´s MIDI library we can use the "raw midi device". This is
the same way on OSS and ALSA. Its just opening the device file and reading or
writing to it
the MIDI bytes. Currently we don´t support MIDI for accessing the internal
(should we ?).


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