求大神,解决linux下ALSA音频开发关于参数设置的问题
本人菜鸟,下面程序是网上非常通用的程序:
//1. 打开PCM,最后一个参数为0意味着标准配置
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结构体
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. 初始化访问权限
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. 初始化采样格式SND_PCM_FORMAT_S16_LE
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. 设置采样率,如果硬件不支持我们设置的采样率,将使用最接近的
val = 8000;//,有些录音采样频率固定为8KHz(8000)
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. 设置通道数量
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*50; //可以将此处增大50倍,可以使分配缓存区变大,
periodsize = frames * 2; //64
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. 设置hw_params
ret = snd_pcm_hw_params(playback_handle, hw_params);
if (ret < 0) {
perror("snd_pcm_hw_params");
exit(1);
}