Hello
I have issues with the on-chip audio PHY of an Orange Pi Zero. This
hardware seems to block the input stream if you
record from it ("audio open error: Device or resource busy"). The
canonical workaround for this appears to be dsnoop.
Indeed, the following asound config allows for multiple simultaneous
recorders:
pcm.dsnooped {
type dsnoop
ipc_key 321465
slave {
pcm "hw:0,0"
channels 2
}
}
However, I also wish to use LADSPA to filter my input. Thus, I have to
chain the aforementioned "dsnooped" block
to a filter block, which I implemented as follows:
pcm.filtered {
type ladspa
slave.pcm "dsnooped";
path "/usr/lib/ladspa";
plugins [{
label highpass_iir
input {
controls [ 200 10 ]
}
}]
}
Any attempt to record from this fails, however:
$ arecord -f dat -V stereo -Dplug:filtered test.wav
Recording WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
Stereo
ALSA lib pcm_params.c:2226:(snd1_pcm_hw_refine_slave) Slave PCM not
usable
arecord: set_params:1310: Broken configuration for this PCM: no
configurations available
The filter itself does, however, work: If I replace the slave line with
slave.pcm "plughw:0,0";
then I get a proper recording, but once again I cannot record multiple
streams simultaneously. I have some ideas
why this may be but I am unsure and generally lost when it comes down to
addressing this. Thus, any help is
appreciated. This is not the first time I am fighting asoundrc, thus I
would be particularly interested in how
to debug this, rather than what the solution is.
Software: Headless armbian buster with linux 5.10.34-sunxi and
libasound2:armhf 1.1.8-1, no PA. alsa-info.sh here:
http://alsa-project.org/db/?f=8c730f1074ebfc0dc7726c3c0ee4ad2214608afe
Best regards and thank you
Matt
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