[PD] HDSP - ALSA - OSS - PD - Confusion

[matthijs at devdsp.net]

PD uses OSS unless you specifically enable ALSA by invoking it thus:

pd -alsa


On Tue, Jul 22, 2003 at 08:06:01AM +0000, Iain Mott wrote:
> Hello
> 
> after a good deal of pain and discomfort I have a HDSP/Multiface unit 
> running with ALSA (the latest CVS) and to my amazement just now, with Pd.
> 
> The only version of Pd that seems to work with my setup is this CVS 
> version (0.37 TEST 4) - (incidentally, fiddle~ seems to be broken in this 
> release). I configured the compilation using the --enable-alsa flag, 
> however I'm not certain it's actually using ALSA. When Pd starts in 
> verbose mode I get the following print out:
> 
> 
> [iain at mother src]$ /home/iain/projects/puredata/pd/bin/pd -mididev 1  
> -verbose -channels 18
> Pd version 0.37 TEST 4
> compiled 16:15:21 Jul 22 2003
> device 1: tried /dev/midi READ/WRITE; returned 3
> opened 1 MIDI input device(s) and 1 MIDI output device(s).
> input channels = 18, output channels = 18
> opened /dev/dsp for reading and writing
>  
> opened audio output on /dev/dsp; got 18 channels
> bytes per sample = 2
> warning: OSS takes only power of 2 blocksize; using 227
> setting nfrags = 8, fragsize 9216
>  
> audiobuffer set to 50 msec
> OSS: requested audio buffer size 79380 limited to 18432
> opened audio input device /dev/dsp; got 18 channels
> bytes per sample = 2
> OSS: issuing first ADC 'read' ... ...done.
> port 5400
> Waiting for connection request...
> TCL_LIBRARY="/home/iain/projects/puredata/pd/tcl/library" 
> TK_LIBRARY="/home/iain/projects/puredata/pd/tk/library"  
> "/home/iain/projects/puredata/pd/bin/pd-gui" 5400
> ... connected
> 
> Does the above mean Pd is using "OSS emulation" and not ALSA proper? I'm 
> pretty confused about the whole thing - hope someone can clarify what's 
> going on. I notice the -alsa flag seems to be gone from this version of 
> Pd - don't know if that has anything to do with it. Also, the setup seems 
> to be limited to buffer sizes of 15msec and higher - any less and 
> dropouts occur. How can I improve this? I'm currently running a Vanilla 
> 2.4.20 kernel - will I need low latency patches etc?
> 
> Cheers,
> 
> Iain
> 
> _____
> Iain Mott
> www.reverberant.com
> 
> 
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-- 
take care,

Matthijs de Jonge
http://devdsp.net - news and resources for computer musicians