【实例简介】

基于alsa，linux音频采集实现

【实例截图】

【文件目录】

AudioSamplingApp

├── AudioSamplingApp.cpp

├── AudioSamplingApp.vcxproj

├── AudioSamplingApp.vcxproj.filters

├── ReadMe.txt

├── build

│   ├── CMakeLists.txt

│   ├── aconfig.h

│   ├── formats.h

│   ├── gettext.h

│   └── version.h

└── x64

└── Debug

├── AudioSamplingApp.Build.CppClean.log

├── AudioSamplingApp.log

├── AudioSamplingApp.obj

├── AudioSamplingApp.tlog

│   ├── AudioSamplingApp.lastbuildstate

│   ├── CL.command.1.tlog

│   ├── CL.read.1.tlog

│   ├── CL.write.1.tlog

│   ├── link.command.1.tlog

│   ├── link.read.1.tlog

│   └── link.write.1.tlog

├── audiosamplingapp.obj.enc

├── vc140.idb

└── vc140.pdb

4 directories, 22 files

【核心代码】

int InitAudioCodec()

{

snd_pcm_stream_t stream = SND_PCM_STREAM_CAPTURE;

snd_pcm_hw_params_t *hwparams;

snd_pcm_info_t *info;

snd_pcm_uframes_t* frames;

char* buffer;

int size;

//char *pcm_name = "default";

char *pcm_name = "hw:1,0";

snd_pcm_info_alloca(&info);

int err = snd_output_stdio_attach(&log, stderr, 0);

assert(err >= 0);

int ret, dir;

//打开设备

ret = snd_pcm_open(&pcm_handle, pcm_name, SND_PCM_STREAM_CAPTURE, 0);

if (ret < 0)

{

printf("unable to open device : %s\n", snd_strerror(ret));

exit(1);

}

snd_pcm_hw_params_alloca(&hwparams);

//使用默认参数

snd_pcm_hw_params_any(pcm_handle, hwparams);

//翻译

snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);

//S16小端

snd_pcm_hw_params_set_format(pcm_handle, hwparams, SND_PCM_FORMAT_S16_LE);

//单通道

snd_pcm_hw_params_set_channels(pcm_handle, hwparams, 1);

//采样率

//int val = 44100;

int val = 16000;

snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &val, 0);

//frames = 32;

if (buffer_time == 0 && buffer_frames == 0)

{

int err = snd_pcm_hw_params_get_buffer_time_max(hwparams,

&buffer_time, 0);

assert(err >= 0);

if (buffer_time > 500000)

{

buffer_time = 500000;

}

}

if (period_time == 0 && period_frames == 0)

{

if (buffer_time > 0)

{

period_time = buffer_time / 4;

}

else

{

period_frames = buffer_frames / 4;

}

}

if (period_time > 0)

{

err = snd_pcm_hw_params_set_period_time_near(pcm_handle, hwparams,

&period_time, 0);

}

else

{

err = snd_pcm_hw_params_set_period_size_near(pcm_handle, hwparams,

&period_frames, 0);

}

//frames = 32;

//snd_pcm_hw_params_set_period_size_near(pcm_handle, hwparams, frames, 0);

if (buffer_time > 0)

{

err = snd_pcm_hw_params_set_buffer_time_near(pcm_handle, hwparams,

&buffer_time, 0);

}

else

{

err = snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hwparams,

&buffer_frames);

}

//参数生效

ret = snd_pcm_hw_params(pcm_handle, hwparams);

if (ret < 0)

{

fprintf(stderr, "unable to set hw parameters:%s\n", snd_strerror(ret));

exit(1);

}

//得到一个周期的数据大小

snd_pcm_hw_params_get_period_size(hwparams, &chunk_size, 0);

snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);

//设置一个周期的时间长度

//snd_pcm_hw_params_get_period_time(hwparams, &val,0);

snd_pcm_start(pcm_handle);

snd_pcm_state_t pcm_state = snd_pcm_state(pcm_handle);

printf("State: %s\n", print_pcm_state(pcm_state));

return 0;

}

int SamplingAudio(char** pbuf, int* nsize)

{

snd_pcm_state_t pcm_state = snd_pcm_state(pcm_handle);

if (pcm_state == SND_PCM_STATE_XRUN)

{

int nRet;

if ((nRet = snd_pcm_prepare(pcm_handle)) < 0)

{

printf("xrun(DRAINING): prepare error: %s", snd_strerror(nRet));

return -1;

}

}

else if (pcm_state == SND_PCM_STATE_PREPARED)

{

snd_pcm_start(pcm_handle);

return -1;

}

int count = *nsize;

while (count > 0)

{

int ret = snd_pcm_readi(pcm_handle, *pbuf, count);

if (ret == -EAGAIN || (ret >= 0 && (size_t)ret < count))

{

snd_pcm_wait(pcm_handle, 100);

}

else if (ret == -EPIPE)

{

fprintf(stderr, "overrun occurred\n");

snd_pcm_prepare(pcm_handle);

//return -3;

}

else if (ret == -ESTRPIPE)

{

while ((ret = snd_pcm_resume(pcm_handle)) == -EAGAIN)

{

sleep(1);  /* wait until resume flag is released */

}

if (ret < 0)

{

snd_pcm_prepare(pcm_handle);

}

}

else if (ret < 0)

{

printf(" error from read: %s", snd_strerror(ret));

return -3;

}

if (ret > 0)

{

static FILE* g_enfp = NULL;

if (!g_enfp)

{

char file_name_264[256] = { 0 };

snprintf(file_name_264, 256, "./AudioSamplingApp.cm");

g_enfp = fopen(file_name_264, "wb");

}

if (g_enfp)

{

fwrite(*pbuf, 1, count, g_enfp);

}

count -= ret;

}

}

return 0;

}