is there an example of a full-duplex ALSA connection in C? I've read that it is supported, but all the introductory examples I saw did either record or play a sound sample, but I'd like to have one handler that can do both for my VoIP-app.
Big thanks for help, Jens
See also latency.c
, included in alsa-lib
source; on the ALSA wiki:
You provide a link to both handles and pump them in turn. Here's alan's code elided and commented.
// the device plughw handle dynamic sample rate and type conversion.
// there are a range of alternate devices defined in your alsa.conf
// try:
// locate alsa.conf
// and check out what devices you have in there
//
// The following device is PLUG:HW:Device:0:Subdevice:0
// Often simply plug, plughw, plughw:0, will have the same effect
//
char *snd_device_in = "plughw:0,0";
char *snd_device_out = "plughw:0,0";
// handle constructs to populate with our links
snd_pcm_t *playback_handle;
snd_pcm_t *capture_handle;
//this is the usual construct... If not fail BLAH
if ((err = snd_pcm_open(&playback_handle, snd_device_out, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
fprintf(stderr, "cannot open output audio device %s: %s\n", snd_device_in, snd_strerror(err));
exit(1);
}
// And now the CAPTURE
if ((err = snd_pcm_open(&capture_handle, snd_device_in, SND_PCM_STREAM_CAPTURE, 0)) < 0) {
fprintf(stderr, "cannot open input audio device %s: %s\n", snd_device_out, snd_strerror(err));
exit(1);
}
then config and pump them.
A ring mod could do the job: http://soundprogramming.net/programming_and_apis/creating_a_ring_buffer or you could use alans way outlined above.
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