Alsa: Combining Type "Dsnoop" with Type "Fifo"
I Am Trying to Get My Linux Audio System to Handle Audio via Alsa. These Are the Requirements Handle Echo Cancellation - I Am Using, Following the Steps...
I am trying to get my Linux audio system to handle audio via ALSA. These are the requirements
- Handle echo cancellation - I am using , following the steps mentioned and it works independently without a problem
- Divide the echo canceled stream to 2
- One going into a noise-canceling plugin again works independently, the audio output of this is used by a different program
- The other to a compressor, the audio output of this will be the default device
Problem
I am facing problems in using "dsnoop" to share/divide the audio stream into two. When dsnoop plugins' slave is set to be a FIFO it throws an error.
executed:
sudo arecord -D default -f cd defRecording.wav -c 1 -r 32000
error:
ALSA lib pcm_direct.c:1809:(_snd_pcm_direct_get_slave_ipc_offset) Invalid type 'fifo' for slave PCM
arecord: main:828: audio open error: Invalid argument
This is the current asound.conf settings
asound.conf
pcm.!default {
type asym
playback.pcm "playback"
capture.pcm "capture"
}
pcm.playback {
type plug
slave.pcm "eci"
}
# Stream Output 1: Final
pcm.capture {
type plug
slave.pcm "compressor"
}
# Stream Output 2: Final
pcm.capture2 {
type plug
slave.pcm "werman"
}
# Stream output 2: Noise Cancellation
pcm.werman {
type ladspa
slave.pcm "array";
path "/usr/lib/ladspa";
plugins [{
label noise_suppressor_mono
input {
# VAD Threshold %
controls [ 1 ]
}
}]
}
# Stream output 1: Compressor
pcm.compressor {
type ladspa
slave.pcm "array";
path "/usr/lib/ladspa";
plugins [{
label dysonCompress
input {
#peak limit, release time, fast ratio, ratio
controls [0 1 0.5 0.99]
}
}]
}
# Used to share the record device
pcm.array {
type dsnoop
slave {
pcm "eco"
channels 1
}
ipc_key 666666
}
# Writes audio coming from any sort of player to ec.input, this is read by the echo
# cancellation software.
pcm.eci {
type plug
slave {
format S16_LE
rate 32000
channels 1
pcm {
type file
slave.pcm null
file "/tmp/ec.input"
format "raw"
}
}
}
# Read FIFO output which contains echo cancelled audio
pcm.eco {
type plug
slave.pcm {
type fifo
infile "/tmp/ec.output"
rate 32000
format S16_LE
channels 1
}
#ipc_key 666666
}Note: eco is used to read the FIFO file which contains the echo canceled audio coming in from cancellation software. This software's input is hw:0 and records audio directly from the microphone, and then processes and passes this over to ec.output
Dsnoop works well when the slave.pcm is a hardware device but as soon as I point to something else it fails. Is there a workaround or any other solution to tackle this problem?
1 Answer
Dsnoop can only have a hardware slave so it can not take in a FIFO plugin as an input. To solve this, I made the echo cancellation software output data into 2 different FIFO files and then read that via ALSA.
James Sterling reports on renewable energy developments, climate policy, ecological conservation, and green tech innovations around the globe.
