宝塔服务器面板,一键全能部署及管理,送你10850元礼包,点我领取
int snd_pcm_hw_params_malloc (snd_pcm_hw_params_t **ptr)
int snd_pcm_hw_params_any (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
void snd_pcm_hw_params_free (snd_pcm_hw_params_t *obj)
int snd_pcm_hw_params_set_access ( snd_pcm_t *pcm,
snd_pcm_hw_params_t *params,
snd_pcm_access_t _access)
int snd_pcm_hw_params_set_format ( snd_pcm_t *pcm,
snd_pcm_hw_params_t *params,
snd_pcm_format_t val)
int snd_pcm_hw_params_set_channels(snd_pcm_t *pcm,
snd_pcm_hw_params_t *params,
unsigned int val)
int snd_pcm_hw_params_set_rate_near(snd_pcm_t *pcm,
snd_pcm_hw_params_t *params,
unsigned int *val, int *dir)
int snd_pcm_hw_params (snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
int snd_pcm_prepare (snd_pcm_t *pcm)
int snd_pcm_open (snd_pcm_t **pcm, const char *name,
snd_pcm_stream_t stream, int mode)
int snd_pcm_close (snd_pcm_t *pcm)
snd_pcm_sframes_t snd_pcm_writei (snd_pcm_t *pcm,
const void *buffer, snd_pcm_uframes_t size)
SND_PCM_ACCESS_RW_INTERLEAVED
SND_PCM_ACCESS_RW_NONINTERLEAVED
SND_PCM_FORMAT_S16_LE 有符号16 bit Little Endian
SND_PCM_FORMAT_S16_BE 有符号16 bit Big Endian
SND_PCM_FORMAT_U16_LE 无符号16 bit Little Endian
SND_PCM_FORMAT_U16_BE 无符号 16 bit Big Endian
比如对于 32-bit 长度的采样数据可以设置为:
SND_PCM_FORMAT_S32_LE 有符号32 bit Little Endian
SND_PCM_FORMAT_S32_BE 有符号32 bit Big Endian
SND_PCM_FORMAT_U32_LE 无符号32 bit Little Endian
SND_PCM_FORMAT_U32_BE 无符号 32 bit Big Endian
/* open a PCM device */
int open_device(struct mad_header const *header)
{
int err;
snd_pcm_hw_params_t *hw_params;
char *pcm_name = “plughw:0,0”;
int rate = header->samplerate;
int channels = 2;
if (header->mode == 0) {
channels = 1;
} else {
channels = 2;
}
if ((err = snd_pcm_open (&playback_handle,
pcm_name, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
printf(“cannot open audio device %s (%s)
“,
pcm_name,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
printf(“cannot allocate hardware parameter structure (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
printf(“cannot initialize hardware parameter structure (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params,
SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
printf(“cannot set access type (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_set_format (playback_handle,
hw_params, SND_PCM_FORMAT_S32_LE)) < 0) {
printf(“cannot set sample format (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_set_rate_near (playback_handle,
hw_params, &rate, 0)) < 0) {
printf(“cannot set sample rate (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params_set_channels (playback_handle,
hw_params, channels)) < 0) {
printf(“cannot set channel count (%s)
“,
snd_strerror (err));
return -1;
}
if ((err = snd_pcm_hw_params (playback_handle,
hw_params)) < 0) {
printf(“cannot set parameters (%s)
“,
snd_strerror (err));
return -1;
}
snd_pcm_hw_params_free (hw_params);
if ((err = snd_pcm_prepare (playback_handle)) < 0) {
printf(“cannot prepare audio interface for use (%s)
“,
snd_strerror (err));
return -1;
}
return 0;
}
while (nsamples–) {
/* nsamples 是采样的数目 */
signed int sample;
sample = pcm->samples[0][j];
*(OutputPtr++) = sample & 0xff;
*(OutputPtr++) = (sample >> 8);
*(OutputPtr++) = (sample >> 16);
*(OutputPtr++) = (sample >> 24);
if (nchannels == 2) {
sample = pcm->samples[1][j];
*(OutputPtr++) = sample & 0xff;
*(OutputPtr++) = sample >> 8;
*(OutputPtr++) = (sample >> 16);
*(OutputPtr++) = (sample >> 24);
}
j++;
}
if ((err = snd_pcm_writei (playback_handle, buf, samples)) < 0) {
err = xrun_recovery(playback_handle, err);
if (err < 0) {
printf(“Write error: %s
“, snd_strerror(err));
return -1;
}
}
int xrun_recovery(snd_pcm_t *handle, int err)
{
if (err == -EPIPE) { /* under-run */
err = snd_pcm_prepare(handle);
if (err < 0)
printf(“Can’t recovery from underrun, prepare failed: %s
“,
snd_strerror(err));
return 0;
} else if (err == -ESTRPIPE) {
while ((err = snd_pcm_resume(handle)) == -EAGAIN)
sleep(1); /* wait until the suspend flag is released */
if (err < 0) {
err = snd_pcm_prepare(handle);
if (err < 0)
printf(“Can’t recovery from suspend, prepare failed: %s
“,
snd_strerror(err));
}
return 0;
}
return err;
}
int mp3_decode_buf(char *input_buf, int size)
{
int decode_over_flag = 0;
int remain_bytes = 0;
int ret_val = 0;
mad_stream_buffer(&decode_stream, input_buf, size);
decode_stream.error = MAD_ERROR_NONE;
while (1)
{
if (decode_stream.error == MAD_ERROR_BUFLEN) {
if (decode_stream.next_frame != NULL) {
remain_bytes = decode_stream.bufend – decode_stream.next_frame;
memcpy(input_buf, decode_stream.next_frame, remain_bytes);
return remain_bytes;
}
}
ret_val = mad_frame_decode(&decode_frame, &decode_stream);
/* 省略部分代码 */
…
if (ret_val == 0) {
if (play_frame(&decode_frame) == -1) {
return -1;
}
}
/* 后面代码省略 */
…
}
return 0;
}
recommend from :http://www.ibm.com/developerworks/cn/linux/l-cn-libmadmp3player/index.html |