#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
int main()
{
int i;int argc11=2;
int ret;
int buf[128];
unsigned int val;
int dir=0;
char *buffer;
int size;char*argv;
argv="/opt/.wc.wav";
snd_pcm_uframes_t frames;
snd_pcm_uframes_t periodsize;
snd_pcm_t *playback_handle;//PCM設備句柄pcm.h
snd_pcm_hw_params_t *hw_params;//硬體資訊和PCM流配置
if (argc11 != 2) {
printf("error: alsa_play_test [music name]\n");
exit(1);
}
printf("play song %s by wolf\n", argv);
FILE *fp = fopen(argv, "rb");
if(fp == NULL)
return 0;
fseek(fp, 100, SEEK_SET);
//1. 打開PCM，最后一個引數為0意味著標準配置
ret = snd_pcm_open(&playback_handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
if (ret < 0) {
perror("snd_pcm_open");
exit(1);
}
//2. 分配snd_pcm_hw_params_t結構體
ret = snd_pcm_hw_params_malloc(&hw_params);
if (ret < 0) {
perror("snd_pcm_hw_params_malloc");
exit(1);
}
//3. 初始化hw_params
ret = snd_pcm_hw_params_any(playback_handle, hw_params);
if (ret < 0) {
perror("snd_pcm_hw_params_any");
exit(1);
}
//4. 初始化訪問權限
ret = snd_pcm_hw_params_set_access(playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
if (ret < 0) {
perror("snd_pcm_hw_params_set_access");
exit(1);
}
//5. 初始化采樣格式SND_PCM_FORMAT_U8,8位
ret = snd_pcm_hw_params_set_format(playback_handle, hw_params, SND_PCM_FORMAT_S16_LE);
if (ret < 0) {
perror("snd_pcm_hw_params_set_format");
exit(1);
}
//6. 設定采樣率，如果硬體不支持我們設定的采樣率，將使用最接近的
//val = 44100,有些錄音采樣頻率固定為8KHz
val = 16000;
ret = snd_pcm_hw_params_set_rate_near(playback_handle, hw_params, &val, &dir);
if (ret < 0) {
perror("snd_pcm_hw_params_set_rate_near");
exit(1);
}
//7. 設定通道數量 1
ret = snd_pcm_hw_params_set_channels(playback_handle, hw_params, 1);
if (ret < 0) {
perror("snd_pcm_hw_params_set_channels");
exit(1);
}
/* Set period size to 32 frames. */
frames = 32;
periodsize = frames ;
ret = snd_pcm_hw_params_set_buffer_size_near(playback_handle, hw_params, &periodsize);
if (ret < 0)
{
printf("Unable to set buffer size %li : %s\n", frames * 2, snd_strerror(ret));
}
periodsize /= 2;
ret = snd_pcm_hw_params_set_period_size_near(playback_handle, hw_params, &periodsize, 0);
if (ret < 0)
{
printf("Unable to set period size %li : %s\n", periodsize, snd_strerror(ret));
}
//8. 設定hw_params
ret = snd_pcm_hw_params(playback_handle, hw_params);
if (ret < 0) {
perror("snd_pcm_hw_params");
exit(1);
}
/* Use a buffer large enough to hold one period */
snd_pcm_hw_params_get_period_size(hw_params, &frames, &dir);
size = frames * 2; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
fprintf(stderr,
"size = %d\n",
size);
while (1)
{
ret = fread(buffer, 1, size, fp);
if(ret == 0)
{
fprintf(stderr, "end of file on input\n");
break;
}
else if (ret != size)
{
}
//9. 寫音頻資料到PCM設備
while(ret = snd_pcm_writei(playback_handle, buffer, frames)<0)
{
usleep(2000);
if (ret == -EPIPE)
{
/* EPIPE means underrun */
fprintf(stderr, "underrun occurred\n");
//完成硬體引數設定，使設備準備好
snd_pcm_prepare(playback_handle);
}
else if (ret < 0)
{
fprintf(stderr,
"error from writei: %s\n",
snd_strerror(ret));
}
}
}
//10. 關閉PCM設備句柄
snd_pcm_close(playback_handle);
return 0;
}
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