On Tue, 12 Jan 2016 03:21:16 +0100, Sergey wrote:
Hello.
I needed a tool to test if anything loud is playing right now. So I wrote "ahwmon" - alsa hw monitoring tool. It's based on dmix idea: it gets "hw" shared playback buffer, but reads from the buffer instead of writing.
Code is mostly copied from alsa-lib, but it uses kernel /dev/snd/pcm* files directly and doesn't depend on alsa-lib or dmix. May work for other apps playing to "hw", including pulseaudio and jackd.
What do you think about it? Can something like this get into alsa-lib or alsa-utils or alsa-plugins? It could be a capture side of "dmix" plugin, which has no capture now. Maybe someone with strong dmix knowledge can port it to dmix?
This is an interesting idea. I like the simplicity of your method, despite the known limitations. I suppose it can be well implemented as a normal alsa-lib plugin?
thanks,
Takashi
Build: gcc -o ahwmon ahwmon.c
Usage: ./ahwmon [-v] [-v] <card_index> <device_index> [<subdevice_index>] subdevice 0 is used by default it outputs .wav stream to stdout
Use cases:
- Card VUmeter: ./ahwmon 0 0 | aplay -V stereo -D null
- Dump what you hear: ./ahwmon 0 0 > audiodump.wav
- Duplicate output of one card to another: ./ahwmon 0 0 | aplay -D plughw:1,0
- Stream what you hear to another pc: ./ahwmon 0 0 | nc 192.168.1.10 12345
Known limitations:
- supports S16_LE and S32_LE only.
- breaks clients attempting to close and reopen "hw"
Any ideas are welcome!
Sergey