Add device selector option.
Like speaker-test -D.

Hello Johnliu.
I'm not a C coder, but i tryed to transform your code in a stereo meter to get the dsnoop virtual sound card to monitor recorded/streamed (stereo) signal.

the attached code is a mare duplication of your, but obviusly is segmentating (no compilation error altough). I suppose a stereo signal has a returning sample of twice the data and have to be slitted in lower (L) and upper(sample data), but do not know how to do that.

Attached my modded code, could you help me making your smart code a more flexible vumeter application?

Thanks,
Federico

sound_meter.c.txt

But it compiles just nice with clang version 3.8.0-2ubuntu4, and the executable works smoothly.

The errors that I get if I run make (with gcc) are:

/tmp/ccqMjrgS.o: In function rms': sound_meter.c:(.text+0x7b): undefined reference to sqrt'
/tmp/ccqMjrgS.o: In function main': sound_meter.c:(.text+0x122): undefined reference to snd_pcm_open'
sound_meter.c:(.text+0x135): undefined reference to snd_strerror' sound_meter.c:(.text+0x181): undefined reference to snd_pcm_set_params'
sound_meter.c:(.text+0x198): undefined reference to snd_strerror' sound_meter.c:(.text+0x1f2): undefined reference to snd_pcm_readi'
sound_meter.c:(.text+0x216): undefined reference to snd_pcm_recover' sound_meter.c:(.text+0x22d): undefined reference to snd_strerror'
sound_meter.c:(.text+0x298): undefined reference to `log10'
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'sound_meter' failed
make: *** [sound_meter] Error 1