I have a Maudio Delta 1010 sound card with 8 input channels and I want to capture pcm data from each input simutanuously ,but I can only capture data from the first and second channel. I user Alsa apis to do this.
How could I capture from other channels
here is my code:
/*
This example reads from the default PCM device
and writes to standard output for 5 seconds of data.
*/
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
int main()
{
long loops;
int rc;
int size;
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
unsigned int val;
int dir;
snd_pcm_uframes_t frames;
char *buffer;
FILE * p;
FILE * log_fp;
int i;
snd_pcm_uframes_t bufferreq;
int count = 0;
int channels = 2;
i = 1;
p = fopen("/home/test/out.pcm", "wb");
log_fp = fopen("/tmp/pcm.log", "wb");
/* Open PCM device for recording (capture). */
rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_CAPTURE, 0);
if (rc < 0)
{
fprintf(stderr, "unable to open pcm device: %sn", snd_strerror(rc));
exit(1);
}
printf(" open device rc = %dn", rc);
/* Allocate a hardware parameters object. */
snd_pcm_hw_params_alloca(¶ms);
/* Fill it in with default values. */
snd_pcm_hw_params_any(handle, params);
/* Set the desired hardware parameters. */
/* Interleaved mode */
snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
/* Signed 16-bit little-endian format */
snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
/* Two channels (stereo) */
snd_pcm_hw_params_set_channels(handle, params, channels);
/* 44100 bits/second sampling rate (CD quality) */
val = 44100;
snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);
/* Set period size to 32 frames. */
frames = 1024;
snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
// bufferreq = 1024 * 1024;
// snd_pcm_hw_params_set_buffer_size_near(handle, params, &bufferreq);
/* Write the parameters to the driver */
rc = snd_pcm_hw_params(handle, params);
if (rc < 0)
{
fprintf(stderr, "unable to set hw parameters: %sn", snd_strerror(rc));
exit(1);
}
/* Use a buffer large enough to hold one period */
snd_pcm_hw_params_get_period_size(params, &frames, &dir);
size = frames * channels * 2; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params, &val, &dir);
loops = 5000000 / val;
while (loops > 0)
{
memset(buffer,0,size);
loops--;
rc = snd_pcm_readi(handle, buffer, frames);
{
//printf("snd_pcm_readin");
if (rc == -EPIPE)
{
/* EPIPE means overrun */
fprintf(stderr, "overrun occurredn");
printf("overrun occurredn");
snd_pcm_prepare(handle);
}
else if (rc < 0)
{
fprintf(stderr, "error from read: %sn", snd_strerror(rc));
printf("error from read: %sn", snd_strerror(rc));
}
else if (rc != (int) frames)
{
fprintf(stderr, "short read, read %d framesn", rc);
printf("short read, read %d framesn", rc);
}
}
count = size + count;
printf("read data %d, %d, %dn", size, i++, rc);
fprintf(log_fp, "%d %dn", size, count);
fwrite(buffer, 1, size, p);
}
snd_pcm_drain(handle);
//snd_pcm_close(handle);
//free(buffer);
return 0;
}