1、opencore-amr源码下载

https://sourceforge.net/projects/opencore-amr/files/opencore-amr/

2、opencore-amr编译

交叉编译到arm平台

./configure --host=arm-linux-gnueabihf --prefix='/home/dong/pocdemo/opencore-amr-0.1.3/arm'

make

make install

3、opencore-amr的应用

1) opencore-amr静态库的使用
arm-linux-gnueabihf-g++ -o demo demo.c -I ./opencore-amr/include/opencore-amrnb libpoc.a ./opencore-amr/lib/libopencore-amrnb.a -lpthread

2) opencore-amr动态库的使用
arm-linux-gnueabihf-g++ -o demo demo.c -I ./opencore-amr/include/opencore-amrnb -L ./ -lpoc -L ./opencore-amr/lib -lopencore-amrnb -lpthread

3) opencore-amr静态库动态库混合的使用
arm-linux-gnueabihf-g++ -o demo demo.c -I ./opencore-amr/include/opencore-amrnb -L ./ -lpoc ./opencore-amr/lib/libopencore-amrnb.a -lpthread

4、源码包里的 opencore-amr/test/amrnb-enc-sine.c

编码一段正玄波

  1. /* ------------------------------------------------------------------
  2.  * Copyright (C) 2009 Martin Storsjo
  3.  *
  4.  * Licensed under the Apache License, Version 2.0 (the "License");
  5.  * you may not use this file except in compliance with the License.
  6.  * You may obtain a copy of the License at
  7.  *
  8.  *      http://www.apache.org/licenses/LICENSE-2.0
  9.  *
  10.  * Unless required by applicable law or agreed to in writing, software
  11.  * distributed under the License is distributed on an "AS IS" BASIS,
  12.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
  13.  * express or implied.
  14.  * See the License for the specific language governing permissions
  15.  * and limitations under the License.
  16.  * -------------------------------------------------------------------
  17.  */
  18.  
  19. #include <stdio.h>
  20. #include <stdint.h>
  21. #include <math.h>
  22. #include <interf_enc.h>
  23.  
  24. int main(int argc, char *argv[]) {
  25.     int i, j;
  26.     void* amr;
  27.     FILE* out;
  28.     int sample_pos = ;
  29.  
  30.     if (argc < ) {
  31.         fprintf(stderr, "%s out.amr\n", argv[]);
  32.         return ;
  33.     }
  34.  
  35.     amr = Encoder_Interface_init();
  36.     out = fopen(argv[], "wb");
  37.     if (!out) {
  38.         perror(argv[]);
  39.         return ;
  40.     }
  41.  
  42.     fwrite("#!AMR\n", , , out);
  43.     for (i = ; i < ; i++) {
  44.         short buf[];
  45.         uint8_t outbuf[];
  46.         int n;
  47.         for (j = ; j < ; j++) {
  48.             buf[j] = *sin(**3.141592654*sample_pos/);
  49.             sample_pos++;
  50.         }
  51.         n = Encoder_Interface_Encode(amr, MR475, buf, outbuf, );
  52.         fwrite(outbuf, , n, out);
  53.     }
  54.     fclose(out);
  55.     Encoder_Interface_exit(amr);
  56.  
  57.     return ;
  58. }

arm-linux-gnueabihf-gcc -o amrnb-enc-sine amrnb-enc-sine.c -I ./opencore-amr/include/opencore-amrnb ./opencore-amr/lib/libopencore-amrnb.a

5、PCM与AMR互转

https://github.com/gansidui/pcm_amr_codec

dong@ubuntu:~/amr/example$ tree
.
├── build_example_amr2pcm_arm.sh
├── build_example_pcm2amr_x86.sh
├── codec
│   ├── amrnb.c
│   ├── amrnb.h
│   ├── audio_format_convert.c
│   ├── audio_format_convert.h
│   └── bs.h
├── dec
├── example_amr2pcm.c
├── example_pcm2amr.c
├── libopencore-amrnb.so.0
├── opencore-amr
│   ├── include
│   │   ├── opencore-amrnb
│   │   │   ├── interf_dec.h
│   │   │   └── interf_enc.h
│   │   └── opencore-amrwb
│   │       ├── dec_if.h
│   │       └── if_rom.h
│   └── lib
│       ├── libopencore-amrnb.a
│       ├── libopencore-amrnb.la
│       ├── libopencore-amrnb.so -> libopencore-amrnb.so.0.0.3
│       ├── libopencore-amrnb.so.0 -> libopencore-amrnb.so.0.0.3
│       ├── libopencore-amrnb.so.0.0.3
│       ├── libopencore-amrwb.a
│       ├── libopencore-amrwb.la
│       ├── libopencore-amrwb.so -> libopencore-amrwb.so.0.0.3
│       ├── libopencore-amrwb.so.0 -> libopencore-amrwb.so.0.0.3
│       ├── libopencore-amrwb.so.0.0.3
│       └── pkgconfig
│           ├── opencore-amrnb.pc
│           └── opencore-amrwb.pc
├── run_dec.sh
├── run_enc.sh
├── test.amr
└── test.amr.pcm

1) gcc可以直接编译

#arm-linux-gnueabihf-gcc example_amr2pcm.c ./codec/audio_format_convert.c ./codec/amrnb.c ./codec/bs.h -o dec -I'./opencore-amr/include/opencore-amrnb' -I'./opencore-amr/include/opencore-amrwb' -I'./codec' ./opencore-amr/lib/libopencore-amrnb.a ./opencore-amr/lib/libopencore-amrwb.a

2) g++和gcc编译需要一点小改动

更改audio_format_convert.h

//#ifdef __cplusplus
//extern "C" {
//#endif

...

...

//#ifdef __cplusplus
//}
//#endif

amrnb.c的第294和368行

int ret = Encoder_Interface_Encode(amrnb_enc, MR475, &samples[offset / sizeof (int16_t)], tmp, amrnb_dtx);

参数mode改成MR475

arm-linux-gnueabihf-g++ example_amr2pcm.c ./codec/audio_format_convert.c ./codec/amrnb.c ./codec/bs.h -o dec -I'./opencore-amr/include/opencore-amrnb' -I'./opencore-amr/include/opencore-amrwb' -I'./codec' ./opencore-amr/lib/libopencore-amrnb.a ./opencore-amr/lib/libopencore-amrwb.a

我的项目整理下编译指令 build.sh

arm-linux-gnueabihf-g++ -o poc_client \
poc_client.c \
./codec/audio_format_convert.c \
./codec/amrnb.c \
./codec/bs.h \
./fifo/app_fifo.c \
./fifo/app_fifo.h \
./list/list.c \
./list/list.h \
-I'./opencore-amr/include/opencore-amrnb' \
-I'./opencore-amr/include/opencore-amrwb' \
-I'./codec' \
./opencore-amr/lib/libopencore-amrnb.a \
./opencore-amr/lib/libopencore-amrwb.a \
./poc/libpoc.a \
-I ./alsa/include -L ./alsa/lib -lasound \
-lpthread

6、alsa播放pcm音频

播放pcm文件

  1. /**alsa play test
  2. *ALSA用户空间编译，ALSA驱动的声卡在用户空间，不宜直接使用
  3. *文件接口中，而应使用alsa-lib
  4. *打开---->设置参数--->读写音频数据 ALSA全部使用alsa-lib中的API
  5. *交叉编译
  6. *export LD_LIBRARY_PATH=$PWD:$LD_LIBRARY_PATH
  7. *arm-linux-gcc -o alsa_play alsa_play_test.c -L. -lasound
  8. *需要交叉编译后的libasound.so库的支持
  9. *
  10. */
  11. #include <stdio.h>
  12. #include <stdlib.h>
  13. #include "alsa/asoundlib.h"
  14.  
  15. int main(int argc, char *argv[])
  16. {
  17.     int i;
  18.     int ret;
  19.     int buf[];
  20.     unsigned int val;
  21.     int dir=;
  22.     char *buffer;
  23.     int size;
  24.     snd_pcm_uframes_t frames;
  25.     snd_pcm_uframes_t periodsize;
  26.     snd_pcm_t *playback_handle;//PCM设备句柄pcm.h
  27.     snd_pcm_hw_params_t *hw_params;//硬件信息和PCM流配置
  28.     if (argc != ) {
  29.         printf("error: alsa_play_test [music name]\n");
  30.         exit();
  31.     }
  32.     printf("play song %s by wolf\n", argv[]);
  33.     FILE *fp = fopen(argv[], "rb");
  34.     if(fp == NULL)
  35.     return ;
  36.     fseek(fp, , SEEK_SET);
  37.  
  38.     //1. 打开PCM，最后一个参数为0意味着标准配置
  39.     ret = snd_pcm_open(&playback_handle, "default", SND_PCM_STREAM_PLAYBACK, );
  40.     if (ret < ) {
  41.         perror("snd_pcm_open");
  42.         exit();
  43.     }
  44.  
  45.     //2. 分配snd_pcm_hw_params_t结构体
  46.     ret = snd_pcm_hw_params_malloc(&hw_params);
  47.     if (ret < ) {
  48.         perror("snd_pcm_hw_params_malloc");
  49.         exit();
  50.     }
  51.     //3. 初始化hw_params
  52.     ret = snd_pcm_hw_params_any(playback_handle, hw_params);
  53.     if (ret < ) {
  54.         perror("snd_pcm_hw_params_any");
  55.         exit();
  56.     }
  57.     //4. 初始化访问权限
  58.     ret = snd_pcm_hw_params_set_access(playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
  59.     if (ret < ) {
  60.         perror("snd_pcm_hw_params_set_access");
  61.         exit();
  62.     }
  63.     //5. 初始化采样格式SND_PCM_FORMAT_U8,8位
  64.     ret = snd_pcm_hw_params_set_format(playback_handle, hw_params, SND_PCM_FORMAT_U8);
  65.     if (ret < ) {
  66.         perror("snd_pcm_hw_params_set_format");
  67.         exit();
  68.     }
  69.     //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
  70.     //val = 44100,有些录音采样频率固定为8KHz
  71.  
  72.     val = ;
  73.     ret = snd_pcm_hw_params_set_rate_near(playback_handle, hw_params, &val, &dir);
  74.     if (ret < ) {
  75.         perror("snd_pcm_hw_params_set_rate_near");
  76.         exit();
  77.     }
  78.     //7. 设置通道数量
  79.     ret = snd_pcm_hw_params_set_channels(playback_handle, hw_params, );
  80.     if (ret < ) {
  81.         perror("snd_pcm_hw_params_set_channels");
  82.         exit();
  83.     }
  84.  
  85.     /* Set period size to 32 frames. */
  86.     frames = ;
  87.     periodsize = frames * ;
  88.     ret = snd_pcm_hw_params_set_buffer_size_near(playback_handle, hw_params, &periodsize);
  89.     if (ret < )
  90.     {
  91.          printf("Unable to set buffer size %li : %s\n", frames * , snd_strerror(ret));
  92.  
  93.     }
  94.           periodsize /= ;
  95.  
  96.     ret = snd_pcm_hw_params_set_period_size_near(playback_handle, hw_params, &periodsize, );
  97.     if (ret < )
  98.     {
  99.         printf("Unable to set period size %li : %s\n", periodsize,  snd_strerror(ret));
  100.     }
  101.  
  102.     //8. 设置hw_params
  103.     ret = snd_pcm_hw_params(playback_handle, hw_params);
  104.     if (ret < ) {
  105.         perror("snd_pcm_hw_params");
  106.         exit();
  107.     }
  108.  
  109.      /* Use a buffer large enough to hold one period */
  110.     snd_pcm_hw_params_get_period_size(hw_params, &frames, &dir);
  111.  
  112.     size = frames * ; /* 2 bytes/sample, 2 channels */
  113.     buffer = (char *) malloc(size);
  114.     fprintf(stderr,
  115.             "size = %d\n",
  116.             size);
  117.  
  118.     while ()
  119.     {
  120.         ret = fread(buffer, , size, fp);
  121.         if(ret == )
  122.         {
  123.               fprintf(stderr, "end of file on input\n");
  124.               break;
  125.         }
  126.         else if (ret != size)
  127.         {
  128.         }
  129.         //9. 写音频数据到PCM设备
  130.         while(ret = snd_pcm_writei(playback_handle, buffer, frames)<)
  131.         {
  132.             usleep();
  133.             if (ret == -EPIPE)
  134.             {
  135.                   /* EPIPE means underrun */
  136.                   fprintf(stderr, "underrun occurred\n");
  137.                   //完成硬件参数设置，使设备准备好
  138.                   snd_pcm_prepare(playback_handle);
  139.             }
  140.             else if (ret < )
  141.             {
  142.                   fprintf(stderr,
  143.                       "error from writei: %s\n",
  144.                       snd_strerror(ret));
  145.             }
  146.         }
  147.  
  148.     }
  149.     //10. 关闭PCM设备句柄
  150.     snd_pcm_close(playback_handle);
  151.  
  152.     return ;
  153. }

arm-linux-gnueabihf-gcc -o test test.c -I ./alsa/include -L ./alsa/lib -lasound -lpthread

./test file.pcm

播放pcm缓存

  1.     #include <alsa/asoundlib.h>
  2.  
  3.     int main()
  4.     {
  5.         int ret;
  6.         snd_pcm_t *pcm_handle;
  7.         snd_pcm_stream_t stream = SND_PCM_STREAM_PLAYBACK;
  8.         snd_pcm_hw_params_t *hwparams;
  9.         char *pcm_name;
  10.  
  11.         pcm_name = strdup("plughw:0,0");
  12.  
  13.         snd_pcm_hw_params_alloca(&hwparams);
  14.  
  15.         ret = snd_pcm_open(&pcm_handle, pcm_name, stream, );
  16.         if (ret < ) {
  17.             printf("snd_pcm_open failed\n");
  18.             return(-);
  19.         }
  20.  
  21.         ret = snd_pcm_hw_params_any(pcm_handle, hwparams);
  22.         if (ret < ) {
  23.             printf("snd_pcm_hw_params_any failed\n");
  24.             return(-);
  25.         }
  26.  
  27.         int rate = ;
  28.         int exact_rate;
  29.         int dir;
  30.         int periods = ;
  31.         snd_pcm_uframes_t periodsize = ;
  32.  
  33.         ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams,
  34.                 SND_PCM_ACCESS_RW_INTERLEAVED);
  35.         if (ret < ) {
  36.             printf("snd_pcm_hw_params_set_access failed\n");
  37.             return(-);
  38.         }
  39.  
  40.         ret = snd_pcm_hw_params_set_format(pcm_handle, hwparams,
  41.                 SND_PCM_FORMAT_S16_LE);
  42.         if (ret < ) {
  43.             printf("snd_pcm_hw_params_set_format failed\n");
  44.             return(-);
  45.         }
  46.  
  47.         exact_rate = rate;
  48.         ret = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams,
  49.                 &exact_rate, );
  50.         if (ret < ) {
  51.             printf("snd_pcm_hw_params_set_rate_near failed\n");
  52.             return(-);
  53.         }
  54.         if (rate != exact_rate) {
  55.             printf("The rate %d Hz is not supported by your hardware\n"
  56.                     "==> Using %d Hz instead\n", rate, exact_rate);
  57.         }
  58.  
  59.         ret = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, );
  60.         if (ret < ) {
  61.             printf("snd_pcm_hw_params_set_channels failed\n");
  62.             return(-);
  63.         }
  64. /*
  65.         ret = snd_pcm_hw_params_set_periods(pcm_handle, hwparams, periods, 0);
  66.         if (ret < 0) {
  67.             printf("snd_pcm_hw_params_set_periods failed\n");
  68.             return(-1);
  69.         }
  70. */
  71.         ret = snd_pcm_hw_params_set_buffer_size(pcm_handle, hwparams,
  72.                 (periodsize * periods) >> );
  73.         if (ret < ) {
  74.             printf("snd_pcm_hw_params_set_buffer_size failed\n");
  75.             return(-);
  76.         }
  77.  
  78.         ret = snd_pcm_hw_params(pcm_handle, hwparams);
  79.         if (ret < ) {
  80.             printf("snd_pcm_hw_params failed\n");
  81.             return(-);
  82.         }
  83.  
  84.         unsigned char *data;
  85.         int l1, l2;
  86.         short s1, s2;
  87.         int frames;
  88.  
  89.         data = malloc(periodsize);
  90.         frames = periodsize >> ;
  91.  
  92.         for (l1 = ; l1 < ; l1++) {
  93.             for (l2 = ; l2 < frames; l2++) {
  94.                 s1 = (l2 % ) *  - ;
  95.                 s2 = (l2 % ) *  - ;
  96.                 data[*l2] = (unsigned char)s1;
  97.                 data[*l2+] = s1 >> ;
  98.                 data[*l2+] = (unsigned char)s2;
  99.                 data[*l2+] = s2 >> ;
  100.             }
  101.             while ((ret = snd_pcm_writei(pcm_handle, data, frames)) < ) {
  102.                 snd_pcm_prepare(pcm_handle);
  103.                 printf("<<<<<<<<<<<<<<Buffer Underrun>>>>>>>>>>>>\n");
  104.             }
  105.         }
  106.  
  107.         snd_pcm_drop(pcm_handle);
  108.         snd_pcm_drain(pcm_handle);
  109.  
  110.         return ;
  111.     }

arm-linux-gnueabihf-gcc -o test test.c -I ./alsa/include -L ./alsa/lib -lasound -lpthread

./test

7、alsa采集pcm音频

采集pcm到缓存/文件

  1. /*
  2. read from the default PCM device and writes to standard output for 5 seconds of data
  3. */
  4.  
  5. #define ALSA_PCM_NEW_HW_PARAMS_API
  6.  
  7. #include <alsa/asoundlib.h>
  8.  
  9. snd_pcm_t * handle;
  10. snd_pcm_hw_params_t * params;
  11. snd_pcm_uframes_t frames;
  12. char * buffer;
  13. unsigned int val;
  14.  
  15. int alsa_capture_init()
  16. {
  17.     int dir;
  18.     int rc;    
  19.  
  20.    /* open PCM device for recording (capture). */
  21.    rc = snd_pcm_open(&handle, "default",SND_PCM_STREAM_CAPTURE,);
  22.    if( rc <  )
  23.    {
  24.         return -;
  25.    }
  26.    /* allocate a hardware parameters object */
  27.    snd_pcm_hw_params_alloca(&params);
  28.    /* fill it with default values. */
  29.    snd_pcm_hw_params_any(handle,params);
  30.    /* set the desired hardware parameters */
  31.    snd_pcm_hw_params_set_access(handle,params,
  32.                                 SND_PCM_ACCESS_RW_INTERLEAVED);
  33.    /* signed 16-bit little-endian format */
  34.    snd_pcm_hw_params_set_format(handle,params,
  35.                                 SND_PCM_FORMAT_S16_LE);
  36.    /* two channels(stereo) */
  37.    snd_pcm_hw_params_set_channels(handle,params,);
  38.    /* sampling rate */
  39.    val = ;
  40.    snd_pcm_hw_params_set_rate_near(handle,params,&val,&dir);
  41.    /* set period size */
  42.    frames = ;
  43.    snd_pcm_hw_params_set_period_size_near(handle,params,&frames,&dir);
  44.    /* write parameters to the driver */
  45.    rc = snd_pcm_hw_params(handle,params);
  46.    if ( rc <  )
  47.    {
  48.         return -;
  49.    }
  50.    /* use a buffer large enough to hold one period */
  51.    snd_pcm_hw_params_get_period_size(params,&frames,&dir);
  52.  
  53.    /* loop for 5 seconds */
  54.    snd_pcm_hw_params_get_period_time(params, &val, &dir);
  55.  
  56.    return ;
  57. }
  58.  
  59. int main()
  60. {
  61.    long loops;
  62.    int ret;
  63.    int size;
  64.    FILE * out_fd;
  65.    out_fd = fopen("out_pcm.raw","wb+");    
  66.  
  67.    alsa_capture_init();
  68.    loops =  / val;
  69.  
  70.    /* 2 bytes/sample, 1 channels */
  71.    size = frames * ;
  72.    buffer = ( char * ) malloc(size);
  73.  
  74.    while( loops >  )
  75.    {
  76.        loops--;
  77.        ret = snd_pcm_readi(handle,buffer,frames);
  78.        if ( ret == -EPIPE )
  79.        {
  80.           /* EPIPE means overrun */
  81.           fprintf(stderr,"overrun occured\n");
  82.           snd_pcm_prepare(handle);
  83.        }
  84.        else if ( ret <  )
  85.        {
  86.           fprintf(stderr,"error from read: %s\n",
  87.                   snd_strerror(ret));
  88.        }
  89.        else if ( ret != (int)frames)
  90.        {
  91.           fprintf(stderr,"short read, read %d frames\n",ret);
  92.        }
  93.  
  94.        ret = fwrite(buffer, , size, out_fd);
  95.        // ret = write(1, buffer, size);
  96.        if ( ret != size )
  97.        {
  98.           fprintf(stderr,"short write: wrote %d bytes\n",ret);
  99.        }
  100.    }
  101.    snd_pcm_drain(handle);
  102.    snd_pcm_close(handle);
  103.    free(buffer);
  104.    fclose(out_fd);
  105. }

arm-linux-gnueabihf-gcc -o test test.c -I ./alsa/include -L ./alsa/lib -lasound -lpthread

./test

8、综合应用实例

采集一段PCM格式语音数据 ，转码成AMR格式然后发送至rtp网络

  1. #if 1
  2.            int i;
  3.            char outbuf[PCM_DATA_LENGTH];
  4.  
  5.            for (i = ; i < *; i++) {
  6.                ret = snd_pcm_readi(handle,buffer,frames);
  7.                if ( ret == -EPIPE )
  8.                {
  9.                   printf("overrun occured\n");
  10.                   snd_pcm_prepare(handle);
  11.                }               
  12.  
  13.                 buffer_pcm2amr_encode((char*)buffer, PCM_DATA_LENGTH, outbuf);
  14.  
  15.                 //n = Encoder_Interface_Encode(amr, MR795, buf, outbuf, 0);
  16.                 amrFrame->m_nFrameLen = ;
  17.                 amrFrame->m_nFrameCount = ;
  18.                 amrFrame->m_pFrame = outbuf;
  19.                 NxZDPttAccess_AmrFrame(snCurCallSessionId, amrFrame);
  20.             }
  21.  
  22. #else
  23.             //------------------------------------
  24.             //sin data test
  25.             int i, j;
  26.             int sample_pos = ;
  27.  
  28.             for (i = ; i < ; i++) {
  29.                 short buf[];
  30.                 char outbuf[];
  31.                 int n;
  32.                 for (j = ; j < ; j++) {
  33.                     buf[j] = *sin(**3.141592654*sample_pos/);
  34.                     sample_pos++;
  35.                 }
  36.                 buffer_pcm2amr_encode((char*)buf, , outbuf);
  37.  
  38.                 //n = Encoder_Interface_Encode(amr, MR515, buf, outbuf, 0);
  39.                 amrFrame->m_nFrameLen = ;
  40.                 amrFrame->m_nFrameCount = ;
  41.                 amrFrame->m_pFrame = outbuf;
  42.                 NxZDPttAccess_AmrFrame(snCurCallSessionId, amrFrame);
  43.             }
  44.             //-------------------------------------
  45. #endif

接收一段AMR格式语音数据，转码成PCM格式，然后写入声卡播放

  1. #if 1
  2.             int i;
  3.             for (i = ; i < pAmrFrame->m_nFrameCount; i++) {
  4.                 int ret = buffer_amr2pcm_decode(pAmrFrame->m_pFrame + i*pAmrFrame->m_nFrameLen, pAmrFrame->m_nFrameLen, pcm_data_buf);
  5.                 if(ret > ){
  6.                     if((ret = snd_pcm_writei(pcm_handle, pcm_data_buf, PCM_DATA_LENGTH/)) < )     {
  7.                         snd_pcm_prepare(pcm_handle);
  8.                         printf("<<<<<<<<<<<<<<Buffer Underrun>>>>>>>>>>>>\n");
  9.                     }
  10.                 }
  11.             }
  12.  
  13. #else
  14.             unsigned char *data;
  15.             int l1, l2;
  16.             short s1, s2;
  17.             int frames;
  18.             int periodsize = ;
  19.             data = (unsigned char*)malloc(periodsize);
  20.             frames = periodsize >> ;
  21.  
  22.             for (l1 = ; l1 < ; l1++) {
  23.                 for (l2 = ; l2 < frames; l2++) {
  24.                     s1 = (l2 % ) *  - ;
  25.                     s2 = (l2 % ) *  - ;
  26.                     data[*l2] = (unsigned char)s1;
  27.                     data[*l2+] = s1 >> ;
  28.                     data[*l2+] = (unsigned char)s2;
  29.                     data[*l2+] = s2 >> ;
  30.                 }
  31.                 if((ret = snd_pcm_writei(pcm_handle, data, frames)) < ) {
  32.                     snd_pcm_prepare(pcm_handle);
  33.                     printf("<<<<<<<<<<<<<<Buffer Underrun>>>>>>>>>>>>\n");
  34.                 }
  35.             }
  36. #endif

9、拓展

tinyalsa做了很多琐事，省了不少时间，感谢作者。

https://github.com/tinyalsa/tinyalsa

generation-sine-wave

https://github.com/ichgw/generation-sine-wave

https://github.com/moutend/getSineWave

https://github.com/munnellg/SineWave

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