Subject: Two chains is one too many (do I need bigger iron?)
From: Joel Roth (jroth_AT_mauigateway.com)
Date: Mon Jul 07 2003 - 23:36:18 EEST
I'm surprised at the xruns I get with multiple chains.
Ecasound running on my 400MHz Celeron PC can
take an input from the soundcard, process
it with reverb, and deliver it to the soundcard
output without overruns.
ecasound -r -X -i:/dev/dsp -rfb:40,0,55 -o:/dev/dsp
However setting up two chains, one for recording
and one for a monitoring, causes massively unnacceptable xruns.
ecasound -c -r -X -b:4096 -f:s16_le,1,44100,n \
-a:monitor -i:backing.wav -o:/dev/dsp \
-a:record -i:/dev/dsp -o:lead.wav
This is a recent (2.2.3) version of ecasound, alsa 0.9.4,
2.4.21-rc7 kernel with low-latency patches.
Top doesn't show much CPU usage, two processes and 5% for one chain.
Running two chains momentarily registers 30% CPU usage, which
drops to about 1% due to some xrun-related effects.
Xruns overwhelm even when one chain is simply routed from null to null,
and with sampling frequence reduced to 22050Hz. This leads me
to think that disk I/O is not a problem. (The IDE disks
were tweaked with hdparm.)
I'll consider shelling out more $$$ for a faster processor, but
wonder if maybe I am missing some other bottleneck in my current
setup.
-- Joel Roth
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