/***playwav.c**注意：这个例子在Ubuntu 12.04.1环境下编译运行成功。**/#include <stdio.h>#include <stdlib.h>#include <alsa/asoundlib.h>int main(int argc, char *argv[]){int i;int ret;int buf[128];unsigned int val;int dir=0;char *buffer;int size;snd_pcm_uframes_t frames;snd_pcm_uframes_t periodsize;snd_pcm_t *playback_handle;//PCM设备句柄pcm.hsnd_pcm_hw_params_t *hw_params;//硬件信息和PCM流配置if (argc != 2) {printf("error: alsa_play_test [music name]\n");exit(1);}printf("play song %s by wolf\n", argv[1]);FILE *fp = fopen(argv[1], "rb");if(fp == NULL)return 0;fseek(fp, 100, SEEK_SET);//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_paramsret = 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_U8,8位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 = 44100,有些录音采样频率固定为8KHzval = 16000;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 1ret = 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;periodsize = frames ;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_paramsret = snd_pcm_hw_params(playback_handle, hw_params);if (ret < 0) {perror("snd_pcm_hw_params");exit(1);}/* Use a buffer large enough to hold one period */snd_pcm_hw_params_get_period_size(hw_params, &frames, &dir);size = frames * 2; /* 2 bytes/sample, 2 channels */buffer = (char *) malloc(size);fprintf(stderr,"size = %d\n",size);while (1){ret = fread(buffer, 1, size, fp);if(ret == 0){fprintf(stderr, "end of file on input\n");break;}else if (ret != size){break;}//9. 写音频数据到PCM设备while(ret = snd_pcm_writei(playback_handle, buffer, frames)<0){usleep(2000);if (ret == -EPIPE){/* EPIPE means underrun */fprintf(stderr, "underrun occurred\n");//完成硬件参数设置，使设备准备好snd_pcm_prepare(playback_handle);}else if (ret < 0){fprintf(stderr,"error from writei: %s\n",snd_strerror(ret));}}if(ret == 1){ret = -1;break;}}//10. 关闭PCM设备句柄snd_pcm_close(playback_handle);return 0;}
注意：编译的时候应该保持“gcc -o playwav playwav.c -L. -lasound”的格式，运行的时候应该保持"./playwav sample.wav"这种格式。
