I have an embedded system with a custom kernel. I have built snd_aloop as a
kernel module and am able to load it. However aplay -l or aplay -L does not
show any devices. However the loopback device is showing up in
/proc/asound/cards so I am wondering what could be the problem.
Details:
# uname -a
Linux openmiko 3.10.14 #7 PREEMPT Sat Sep 5 21:33:15 UTC 2020 mips GNU/Linux
# aplay --version
aplay: version 1.1.0 by Jaroslav Kysela <pe...@perex.cz>
I see the loopback card:
# cat /proc/asound/cards
3 [Loopback ]: Loopback - Loopback
Loopback 1
But aplay -l gives me nothing:
# aplay -l
******************** WARNING *******************************
Warning! aplay uses ALSA emulation instead of the native OSS API
****************************************************************
aplay: device_list:268: no soundcards found...
#
# lsmod
Module Size Used by Tainted: G
snd_aloop 12002 0
snd_pcm 68453 1 snd_aloop
snd_page_alloc 3810 1 snd_pcm
snd_timer 18670 1 snd_pcm
snd 39168 3 snd_aloop,snd_pcm,snd_timer
v4l2loopback 22369 2
sensor_jxf23 9136 1
tx_isp 337860 3
sinfo 12972 0
#
More details:
# cat /proc/asound/
Loopback/ cards modules timers
card3/ devices pcm version
# cat /proc/asound/pcm
03-00: Loopback PCM : Loopback PCM : playback 2 : capture 2
03-01: Loopback PCM : Loopback PCM : playback 2 : capture 2
# cat /proc/asound/modules
3 snd_aloop
# cat /proc/asound/devices
33: : timer
96: [ 3] : control
112: [ 3- 0]: digital audio playback
113: [ 3- 1]: digital audio playback
120: [ 3- 0]: digital audio capture
121: [ 3- 1]: digital audio capture
My goal is to read from /dev/dsp (OSS legacy) and output it to the loopback
device so a program that only uses ALSA can have audio. I plan to use
ffmpeg. Ffmpeg does not see the hardware either.
I have tried variations of:
ffmpeg -f oss -i /dev/dsp -codec:a pcm_s16le -f alsa hw:3,0
ffmpeg -f oss -i /dev/dsp -codec:a pcm_s16le -f alsa hw:3,1
I tried poking around in the kernel sources but no real smoking gun. The
vendor has their own sound device drivers. Is it possible it is somehow
interfering with getting a full device list?
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