下载alsa-lib

alsa-project官网：https://www.alsa-project.org/wiki/Main_Page

安装alsa-lib

配置生成Makefile文件：

./configure --prefix=./build --enable-shared=no --enable-static=yes --enable-debug-assert=yes

make

安装：

make install

使用alsa-lib

设定播放参数

#define goto_error_if_fail(p)                           \
  if (!(p)) {                                           \
    printf("%s:%d " #p "\n", __FUNCTION__, __LINE__);   \
    goto error;                                         \
  }

snd_pcm_t* device_create(void)
{
  snd_pcm_t* handle;            /* pcm句柄 */
  snd_pcm_hw_params_t* params;  /* pcm参数 */
  int rc = -1;

  /* 打开设备 */
  rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK,0);
  goto_error_if_fail(rc >= 0);
  
  /* 初始化pcm属性 */
  rc = snd_pcm_hw_params_alloca(&params);
  goto_error_if_fail(rc >= 0);
  snd_pcm_hw_params_any(handle, params);

   /* 设置为交错模式 */
  snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);

  /* 设置为双声道 */
  snd_pcm_hw_params_set_channels(handle, params, 2);

  /* 设置数据格式: 有符号16位格式 */
  snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16);

  /* 设置采样率 */
  int val = 44100;
  snd_pcm_hw_params_set_rate_near(handle,params,&val,0);

  /* 将参数写入设备 */
  rc = snd_pcm_hw_params(handle, params);
  goto_error_if_fail(rc >= 0);

  return handle;
error:
  snd_pcm_hw_params_free(params);
  snd_pcm_close(handle);
  return NULL;
}

播放pcm音频数据

int device_play(snd_pcm_t* pcm_handle, const void* data, int data_size)
{
  snd_pcm_uframes_t frame_num;
  snd_pcm_uframes_t frame_size;   /* 一帧的大小 */
  unsigned int channels = 2;      /* 双声道 */
  unsigned int format_sbits = 16; /* 数据格式: 有符号16位格式 */
  /* 获取一个播放周期的帧数 */
  snd_pcm_hw_params_get_period_size(params, &frame_num, 0);
  frame_size = channels * format_sbits / 8;

  for(snd_pcm_uframes_t i = 0; i < data_size;)
  {
    int rc = -1;
    /* 播放 */
    rc = snd_pcm_writei(pcm_handle, data + i, frame_num);
    goto_error_if_fail(rc >= 0 || rc == -EPIPE);
    if(rc == -EPIPE)
    {
      /* 让音频设备准备好接收pcm数据 */
      snd_pcm_prepare(handle); 
    }
    else
    {
      i += frame_num * frame_size;
    }
  }
  return 0;
error:
  return -1;
}

关闭播放设备

void device_destroy(snd_pcm_t* pcm_handle)
{
  snd_pcm_drain(pcm_handle);   /* 等待数据全部播放完成 */
  snd_pcm_close(pcm_handle);
}

/* main.c */
int main()
{
  snd_pcm_t* pcm_handle = NULL;
  /* 获取pcm音频数据 */
  char data[40 * 1024];
  FILE* file = fopen("pcm_data", "rb");
  fread(data, sizeof(data[0]), sizeof(data)/sizeof(data[0]), file);
  fclose(file);

  pcm_handle = device_create();
  device_play(pcm_handle, data, sizeof(data)/sizeof(data[0]));
  device_destroy(pcm_handle);
  return 0;
}

编译

gcc -o bin/pcm.out -I./alsa-lib/build/include ./main.c -L./alsa-lib/build/lib -lpthread -lm -ldl -lasound -g