Hi all,
I'm trying to build a full-duplex app using alsa, but I'm having some
problems with getting buffsersizes and timing right. I can't get a simple
record-and-playback app working right without underruns occuring.
I hope some experienced alsa programmers can take a quick look at my
attached piece of code and tell me what I need to do to get this working
right. (or am I just doing things *really* wrong here ?)
Hope to get some helpfull tips,
Ico
os : linx 2.4.20
alsa version: 0.9.4
soundcard: intel810
-----------------------------------------------------------------------------
#include <stdio.h>
#include <sys/time.h>
#include <time.h>
#include <sys/select.h>
#define ALSA_PCM_NEW_HW_PARAMS_API
#define ALSA_PCM_NEW_SW_PARAMS_API
#include <alsa/asoundlib.h>
#include <math.h>
#define PERIODSIZE 512
#define BUFSIZE (PERIODSIZE*4)
char *device = "hw:0,0";
int samplerate = 16000;
int channels = 2;
int accessmode = SND_PCM_ACCESS_RW_INTERLEAVED;
int format = SND_PCM_FORMAT_S16_LE;
int periods = 4;
snd_pcm_uframes_t buffer_size = PERIODSIZE * 4;
snd_pcm_uframes_t period_size = PERIODSIZE;
snd_output_t *output = NULL;
#define checkr(r) if(r<0) { \
fprintf(stderr, "line %d: %s\n", __LINE__, snd_strerror(r)); \
exit(-1); \
}
int set_hw_params(snd_pcm_t *handle, int play)
{
int r;
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
r = snd_pcm_hw_params_malloc(&hwparams); checkr(r);
r = snd_pcm_hw_params_any(handle, hwparams); checkr(r);
r = snd_pcm_hw_params_set_access(handle, hwparams, accessmode); checkr(r);
r = snd_pcm_hw_params_set_format(handle, hwparams, format); checkr(r);
r = snd_pcm_hw_params_set_channels(handle, hwparams, channels); checkr(r);
r = snd_pcm_hw_params_set_rate_near(handle, hwparams, &samplerate, 0);
checkr(r);
r = snd_pcm_hw_params_set_periods(handle, hwparams, periods, 0); checkr(r);
r = snd_pcm_hw_params_set_buffer_size_near(handle, hwparams, &buffer_size);
checkr(r);
r = snd_pcm_hw_params_set_period_size_near(handle, hwparams, &period_size, 0);
checkr(r);
r = snd_pcm_hw_params(handle, hwparams); checkr(r);
snd_pcm_hw_params_free (hwparams);
r = snd_pcm_sw_params_malloc(&swparams); checkr(r);
r = snd_pcm_sw_params_current(handle, swparams); checkr(r);
r = snd_pcm_sw_params_set_avail_min(handle, swparams, period_size); checkr(r);
r = snd_pcm_sw_params(handle, swparams); checkr(r);
snd_pcm_sw_params_free(swparams);
snd_pcm_prepare(handle);
return(0);
}
int main(int argc, char **argv)
{
short buf[BUFSIZE*10];
int r;
snd_pcm_t *pcmr;
snd_pcm_t *pcmp;
r = snd_pcm_open(&pcmr, device, SND_PCM_STREAM_CAPTURE, 0); checkr(r);
set_hw_params(pcmr, 1);
r = snd_pcm_open(&pcmp, device, SND_PCM_STREAM_PLAYBACK, 0); checkr(r);
set_hw_params(pcmp, 1);
while(1) {
r = snd_pcm_readi(pcmr, buf, BUFSIZE);
if(r != BUFSIZE) printf("rec r=%d\n", r);
checkr(r);
r = snd_pcm_writei(pcmp, buf, BUFSIZE);
if(r != BUFSIZE) printf("play r=%d\n", r);
if(r == -EPIPE) {
snd_pcm_prepare(pcmp);
} else {
checkr(r);
}
}
return(0);
}
--
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