Estou tentando capturar e reproduzir áudio usando o programa C. Para isso eu tenho este tutorial. . Aqui está o programa que estou executando: -
/**
* Jan Newmarch
*/
#define PERIOD_SIZE 1024
#define BUF_SIZE (PERIOD_SIZE * 2)
#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
void print_pcm_state(snd_pcm_t *handle, char *name) {
switch (snd_pcm_state(handle)) {
case SND_PCM_STATE_OPEN:
printf("state open %s\n", name);
break;
case SND_PCM_STATE_SETUP:
printf("state setup %s\n", name);
break;
case SND_PCM_STATE_PREPARED:
printf("state prepare %s\n", name);
break;
case SND_PCM_STATE_RUNNING:
printf("state running %s\n", name);
break;
case SND_PCM_STATE_XRUN:
printf("state xrun %s\n", name);
break;
default:
printf("state other %s\n", name);
break;
}
}
int setparams(snd_pcm_t *handle, char *name) {
snd_pcm_hw_params_t *hw_params;
int err;
if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_any (handle, hw_params)) < 0) {
fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_access (handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
fprintf (stderr, "cannot set access type (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_format (handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
fprintf (stderr, "cannot set sample format (%s)\n",
snd_strerror (err));
exit (1);
}
unsigned int rate = 48000;
if ((err = snd_pcm_hw_params_set_rate_near (handle, hw_params, &rate, 0)) < 0) {
fprintf (stderr, "cannot set sample rate (%s)\n",
snd_strerror (err));
exit (1);
}
printf("Rate for %s is %d\n", name, rate);
if ((err = snd_pcm_hw_params_set_channels (handle, hw_params, 2)) < 0) {
fprintf (stderr, "cannot set channel count (%s)\n",
snd_strerror (err));
exit (1);
}
snd_pcm_uframes_t buffersize = BUF_SIZE;
if ((err = snd_pcm_hw_params_set_buffer_size_near(handle, hw_params, &buffersize)) < 0) {
printf("Unable to set buffer size %li: %s\n", BUF_SIZE, snd_strerror(err));
exit (1);;
}
snd_pcm_uframes_t periodsize = PERIOD_SIZE;
fprintf(stderr, "period size now %d\n", periodsize);
if ((err = snd_pcm_hw_params_set_period_size_near(handle, hw_params, &periodsize, 0)) < 0) {
printf("Unable to set period size %li: %s\n", periodsize, snd_strerror(err));
exit (1);
}
if ((err = snd_pcm_hw_params (handle, hw_params)) < 0) {
fprintf (stderr, "cannot set parameters (%s)\n",
snd_strerror (err));
exit (1);
}
snd_pcm_uframes_t p_psize;
snd_pcm_hw_params_get_period_size(hw_params, &p_psize, NULL);
fprintf(stderr, "period size %d\n", p_psize);
snd_pcm_hw_params_get_buffer_size(hw_params, &p_psize);
fprintf(stderr, "buffer size %d\n", p_psize);
snd_pcm_hw_params_free (hw_params);
if ((err = snd_pcm_prepare (handle)) < 0) {
fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
snd_strerror (err));
exit (1);
}
return 0;
}
int set_sw_params(snd_pcm_t *handle, char *name) {
snd_pcm_sw_params_t *swparams;
int err;
snd_pcm_sw_params_alloca(&swparams);
err = snd_pcm_sw_params_current(handle, swparams);
if (err < 0) {
fprintf(stderr, "Broken configuration for this PCM: no configurations available\n");
exit(1);
}
err = snd_pcm_sw_params_set_start_threshold(handle, swparams, PERIOD_SIZE);
if (err < 0) {
printf("Unable to set start threshold: %s\n", snd_strerror(err));
return err;
}
err = snd_pcm_sw_params_set_avail_min(handle, swparams, PERIOD_SIZE);
if (err < 0) {
printf("Unable to set avail min: %s\n", snd_strerror(err));
return err;
}
if (snd_pcm_sw_params(handle, swparams) < 0) {
fprintf(stderr, "unable to install sw params:\n");
exit(1);
}
return 0;
}
/************** some code from latency.c *****************/
main (int argc, char *argv[])
{
int i;
int err;
int buf[BUF_SIZE];
snd_pcm_t *playback_handle;
snd_pcm_t *capture_handle;
snd_pcm_hw_params_t *hw_params;
FILE *fin;
size_t nread;
snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
if (argc != 3) {
fprintf(stderr, "Usage: %s in-card out-card\n", argv[0]);
exit(1);
}
/**** Out card *******/
if ((err = snd_pcm_open (&playback_handle, argv[2], SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
fprintf (stderr, "cannot open audio device %s (%s)\n",
argv[2],
snd_strerror (err));
exit (1);
}
setparams(playback_handle, "playback");
set_sw_params(playback_handle, "playback");
/*********** In card **********/
if ((err = snd_pcm_open (&capture_handle, argv[1], SND_PCM_STREAM_CAPTURE, 0)) < 0) {
fprintf (stderr, "cannot open audio device %s (%s)\n",
argv[1],
snd_strerror (err));
exit (1);
}
setparams(capture_handle, "capture");
set_sw_params(capture_handle, "capture");
if ((err = snd_pcm_link(capture_handle, playback_handle)) < 0) {
printf("Streams link error: %s\n", snd_strerror(err));
exit(0);
}
if ((err = snd_pcm_prepare (playback_handle)) < 0) {
fprintf (stderr, "cannot prepare playback audio interface for use (%s)\n",
snd_strerror (err));
exit (1);
}
/**************** stuff something into the playback buffer ****************/
if (snd_pcm_format_set_silence(format, buf, 2*BUF_SIZE) < 0) {
fprintf(stderr, "silence error\n");
exit(1);
}
int n = 0;
while (n++ < 2) {
if (snd_pcm_writei (playback_handle, buf, BUF_SIZE) < 0) {
fprintf(stderr, "write error\n");
exit(1);
}
}
/************* COPY ************/
while (1) {
int nread;
if ((nread = snd_pcm_readi (capture_handle, buf, BUF_SIZE)) != BUF_SIZE) {
if (nread < 0) {
fprintf (stderr, "read from audio interface failed (%s)\n",
snd_strerror (nread));
} else {
fprintf (stderr, "read from audio interface failed after %d frames\n", nread);
}
snd_pcm_prepare(capture_handle);
continue;
}
if ((err = snd_pcm_writei (playback_handle, buf, nread)) != nread) {
if (err < 0) {
fprintf (stderr, "write to audio interface failed (%s)\n",
snd_strerror (err));
} else {
fprintf (stderr, "write to audio interface failed after %d frames\n", err);
}
snd_pcm_prepare(playback_handle);
}
}
snd_pcm_drain(playback_handle);
snd_pcm_close (playback_handle);
exit (0);
}
Eu compilo e corro com os seguintes argumentos: -
./playback-capture hw:0 hw:0
Até agora meu código está funcionando bem, mas agora eu decido rodar este programa usando uma placa de som USB. Para isso eu edito
/etc/modprobe.d/alsa-base.conf
Aqui estão as alterações: -
Eu substituo
options snd_usb_audio index=-2
options snd_hda_intel index=-1
com
options snd_usb_audio index=-1
options snd_hda_intel index=-2
E eu substituo
# Keep snd-usb-audio from beeing loaded as first soundcard
options snd-usb-audio index=-1
com
# Keep snd-usb-audio from beeing loaded as first soundcard
options snd-usb-audio index=-1
Agora, quando eu executo meu código, recebo esta saída: -
Rate for playback is 48000
period size now 1024
period size 1024
buffer size 2048
Rate for capture is 48000
cannot set channel count (Invalid argument)
Então, alguém pode me dizer o que mais devo fazer para executar meu código usando a placa de som.
Nota: - Eu executo o comando
aplay -l
e obteve esta saída: -
card 0: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC221 Analog [ALC221 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
Tags alsa usb-device audio usb-audio