Hello, I would like to create a simple trigger from a microphone input, using alsa. For example I would like that every time I short-circuit a jack inserted in the "mic hole", my program say "Hello World". I would like that this application will be lightweight (I don't need audio quality, just a trigger!) and that cohexists with other apps that should keep using the output of the same sound card.

My idea was to simply code a raw "snd_pcm_readi" call and after compare each sample of the captured block with a threshold. For instance, if the 90% of sample are above the given threshold, the trigger must act.

Of course it doesn't work :-)

I plug a simple jack in the mic, and open or short-circuit the poles. In the captured block, I can find only samples between 0xFFE0 and 0xFFFF (and some sporadic 0x0000).

Any hits? Thanks

Lorenzo