Hi,
No, this is not about the usual loopback latency ;) I have found a
strange anomaly.
I have 2 sound cards: C-Media CMI8738 (I've check, well supported on
Linux, work great)
1st is for Toslink input, 2nd for Toslink output (and this is the
default and only sink for the whole system)
I'm setting up a loopback device like this:
pactl load-module module-loopback \
latency_msec=1 \
source=alsa_input.pci-0000_06_01.0.iec958-stereo \
sink=alsa_output.pci-0000_06_02.0.iec958-stereo
And this works great! Latency is very low:
Sink Input #0
Driver: module-loopback.c
[...]
Buffer Latency: 10250 usec
Sink Latency: 7263 usec
Source Output #0
Driver: module-loopback.c
[...]
Buffer Latency: 0 usec
Source Latency: 380 usec
Now, here is the problem. When I unplug a cable of the source, source
latency rises to infinity. And I understand why, it's fine, but, when I
plug the cable again, then: source Latency slowly goes down, but sink's
buffer latency rises, up to even 8-12 seconds.
Notes:
- Reloading the module is a fix.
- by unplug I mean unplug, or shut down the source: anything that
stops the signal.
What I'm looking for:
1. This is most likely a bug, which I could help analyze by providing
more data.
2. But in the meantime, I'm looking for a way to reload the module when
source device shows up. This is the best I came up with so far, in tmux:
watch -n 105 'pactl list | grep -A 12 module-loopback.c | grep "Source
Latency" | grep -Eo "[0-9]{9}" &> /dev/null && pactl unload-module
module-loopback && sleep 6 && pactl load-module module-loopback
latency_msec=1 source=alsa_input.pci-0000_06_01.0.iec958-stereo
sink=alsa_output.pci-0000_06_02.0.iec958-stereo && echo "reload"'
(if Source Latency goes over 8 digit number (100seconds), reload the
module-loopback)
--
dextkrk
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