Re: GUS Classic driver, PLUGHW problems

["Ville Syrjälä" <syrjala@sci.fi>]

On Fri, Jul 04, 2003 at 02:12:49AM -0700, Joseph Lunderville wrote:
> I'm trying to get a 486 with a GUS Classic working through ALSA, and I've
> run into a couple of problems:
> 
> 
> 1. plughw doesn't know how to convert from interleaved data to
> noninterleaved data. in fact, as far as I can see, nothing at all except the
> GUS driver knows what to do with noninterleaved data.

I ran into this problem with my GUS PnP some time ago. You should be able
to find the discussion from alsa-devel archives.

Apparently the conversion works for some other non-interleaved cards
like RME Hammerfall. The GUS driver doesn't support mmap which may cause
problems but even using alsa-lib's mmap emulation didn't fix the problem
for me :(

> I imagine that the only
> reason this hasn't been fixed yet is that nobody wants to use a GUS with
> ALSA :)

I will resurrect my GUS PnP when (if?) MIDI emulation gets implemented...

> 2. the GUS driver seems to have a problem with outputting PCM data. I had to
> test it using my own code (since the example uses interleaved data), but I'm
> reasonably confident that the problem's in the driver.
> 
> the problem I'm observing is that there are frequent clicks in the audio
> output (coincidentally, they arrive at a frequency corresponding exactly to
> the size of the ring buffer -- I've confirmed this by looking at the output
> on an oscilloscope. the click looks like one or two samples are being
> skipped). this is when I use a buffer size that's a multiple of my period
> size -- when I use other combinations of buffer size and period size, things
> get worse. some combinations of buffer & period size cause I/O errors.
> 
> 3. finally, the example doesn't start the audio output. it's difficult for
> me to tell whether you're supposed to call snd_pcm_start() in order to get
> output from the speakers (in which case the example is wrong), or whether
> the gus driver requires this when it's not supposed to, but either way
> something's not right.

I don't remember seeing this with my GUS PnP but then again I mostly used
the codec instead of the synth for PCM. Also GUS PnP doesn't have the
channel count vs. frequency limitation of the original GUS.

I have a GUS MAX buried somewhere but I don't think I've tried it with
ALSA.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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