使用 ALSAlib 播放 wav

在 ARM 2440 开发板上正常播放 16bit  44100 采样率的wav ， 为了程序简单，没有判断返回值。

补充，在 ubunto 上也能正常播放。

编译方法： arm-linux-gcc -lasound wplay.c -o wplay  或在 ubuntu 上编译 gcc -lasound wplay.c -o wplay

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <alsa/asoundlib.h>
 #ifndef WORD
 #define WORD unsigned short
 #endif

 #ifndef DWORD
 #define DWORD unsigned int
 #endif

 struct RIFF_HEADER
 {
     char szRiffID[];  // 'R','I','F','F'
     DWORD dwRiffSize;
     char szRiffFormat[]; // 'W','A','V','E'
 };

 struct WAVE_FORMAT
 {
     WORD wFormatTag;
     WORD wChannels;
     DWORD dwSamplesPerSec;
     DWORD dwAvgBytesPerSec;
     WORD wBlockAlign;
     WORD wBitsPerSample;
 };

 struct FMT_BLOCK
 {
     char  szFmtID[]; // 'f','m','t',' '
     DWORD  dwFmtSize;
     struct WAVE_FORMAT wavFormat;
 };

 struct DATA_BLOCK
 {
     char szDataID[]; // 'd','a','t','a'
     DWORD dwDataSize;
 };

 void read_wav(unsigned char *wav_buf, int *fs, int *channels, int *bits_per_sample, int *wav_size, int *file_size)
 {
     struct RIFF_HEADER *headblk;
     struct FMT_BLOCK   *fmtblk;
     struct DATA_BLOCK  *datblk;

     headblk = (struct RIFF_HEADER *) wav_buf;
     fmtblk  = (struct FMT_BLOCK *) &headblk[];
     datblk  = (struct DATA_BLOCK *) &fmtblk[];

     *file_size = headblk->dwRiffSize;

     //采样频率
     *fs         = fmtblk->wavFormat.dwSamplesPerSec;

     //通道数
     *channels  = fmtblk->wavFormat.wChannels;

     *wav_size  = datblk->dwDataSize;
     //采样bit数 16 24
     *bits_per_sample = fmtblk->wavFormat.wBitsPerSample;
 }

 int main(int argc, char ** argv)
 {
     int fs, channels, bits_per_sample, wav_size, file_size;
     unsigned char *wav_buf;
     unsigned char *audio_buf;
     unsigned char *audio_p;
     int fd;
     struct stat stat;

     int size;
     snd_pcm_t *playback_handle;
     snd_pcm_hw_params_t *hw_params;//硬件信息和PCM流配置

     snd_pcm_uframes_t chunk_size = ;
     unsigned int rate;
     snd_pcm_format_t format;

     if( != argc)
     {
         printf("usage:%s wav file\n", argv[]);
         return -;
     }

     fd = open(argv[], O_RDONLY);
     fstat(fd, &stat);
     wav_buf = mmap(NULL, stat.st_size, PROT_READ, MAP_SHARED, fd, );
     read_wav(wav_buf, &fs, &channels, &bits_per_sample, &wav_size, &file_size);
     printf("wav format: fs = %d, channels = %d, bits_per_sample = %d, wav_size = %d file_size = %d\n\r", fs, channels, bits_per_sample, wav_size, file_size);

     //真实wav 跳过头部
     audio_buf = wav_buf + sizeof(struct RIFF_HEADER) + sizeof(struct FMT_BLOCK) + sizeof(struct DATA_BLOCK);

     rate = fs;
     //初始化声卡
     //1. 打开PCM，最后一个参数为0意味着标准配置
     if ( > snd_pcm_open(&playback_handle, "default", SND_PCM_STREAM_PLAYBACK, ))
     {
         printf("snd_pcm_open err\n");
         return -;
     }
     //2. 分配snd_pcm_hw_params_t结构体
     if( > snd_pcm_hw_params_malloc (&hw_params))
     {
         printf("snd_pcm_hw_params_malloc err\n");
         return -;
     }
     //3. 初始化hw_params
     if( > snd_pcm_hw_params_any (playback_handle, hw_params))
     {
         printf("snd_pcm_hw_params_any err\n");
         return -;
     }
     //4. 初始化访问权限
     if ( > snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED))
     {
         printf("snd_pcm_hw_params_any err\n");
         return -;
     }
     //5. 初始化采样格式SND_PCM_FORMAT_U8,8位
     if( == bits_per_sample)
     {
         if ( > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_U8))
         {
             printf("snd_pcm_hw_params_set_format err\n");
             return -;
         }
         format = SND_PCM_FORMAT_U8;
     }

     if( == bits_per_sample)
     {
         if ( > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE))
         {
             printf("snd_pcm_hw_params_set_format err\n");
             return -;
         }
         format = SND_PCM_FORMAT_S16_LE;
     }
     //6. 设置采样率
     if ( > snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, &rate, ))
     {
         printf("snd_pcm_hw_params_set_rate_near err\n");
         return -;
     }
     //7. 设置通道数量
     if ( > snd_pcm_hw_params_set_channels(playback_handle, hw_params, ))
     {
         printf("snd_pcm_hw_params_set_channels err\n");
         return -;
     }

     //8. 设置hw_params
     if ( > snd_pcm_hw_params (playback_handle, hw_params))
     {
         printf("snd_pcm_hw_params err\n");
         return -;
     }

     snd_pcm_hw_params_get_period_size(hw_params, &chunk_size, );

     snd_pcm_hw_params_free (hw_params);
     if ( > snd_pcm_prepare (playback_handle))
     {
         printf("snd_pcm_prepare err\n");
         return -;
     }
     //chunk_size = ?;
     printf("chunk_size:%ld \n", chunk_size);
     audio_p = audio_buf;
     while((audio_p - audio_buf) <= stat.st_size)
     {
         snd_pcm_writei(playback_handle, audio_p, chunk_size);
         audio_p += chunk_size * ; //16位 双声道
     }
     printf("play ok \n");
     snd_pcm_close(playback_handle);
     return ;
 }