pcm_min.c

LINUX下基于ALSA音频驱动的应用程序

/*                                                                                                      
 *  This extra small demo sends a random samples to your speakers.                                      
 */                                                                                                     
                                                                                                        
#include "../include/asoundlib.h"                                                                       
                                                                                                        
static char *device = "default";                        /* playback device */                           
                                                                                                        
snd_output_t *output = NULL;                                                                            
unsigned char buffer[16*1024];                          /* some random data */                          
                                                                                                        
int main(void)                                                                                          
{                                                                                                       
        int err;                                                                                        
        unsigned int i;                                                                                 
        snd_pcm_t *handle;                                                                              
        snd_pcm_sframes_t frames;                                                                       
                                                                                                        
        for (i = 0; i < sizeof(buffer); i++)                                                            
                buffer[i] = random() & 0xff;                                                            
                                                                                                        
        if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {                    
                printf("Playback open error: %s\n", snd_strerror(err));                                 
                exit(EXIT_FAILURE);                                                                     
        }                                                                                               
        if ((err = snd_pcm_set_params(handle,                                                           
                                      SND_PCM_FORMAT_U8,                                                
                                      SND_PCM_ACCESS_RW_INTERLEAVED,                                    
                                      1,                                                                
                                      48000,                                                            
                                      1,                                                                
                                      500000)) < 0) {   /* 0.5sec */                                    
                printf("Playback open error: %s\n", snd_strerror(err));                                 
                exit(EXIT_FAILURE);                                                                     
        }                                                                                               
                                                                                                        
        for (i = 0; i < 16; i++) {                                                                      
                frames = snd_pcm_writei(handle, buffer, sizeof(buffer));                                
                if (frames < 0)                                                                         
                        frames = snd_pcm_recover(handle, frames, 0);                                    
                if (frames < 0) {                                                                       
                        printf("snd_pcm_writei failed: %s\n", snd_strerror(err));                       
                        break;                                                                          
                }                                                                                       
                if (frames > 0 && frames < (long)sizeof(buffer))                                        
                        printf("Short write (expected %li, wrote %li)\n", (long)sizeof(buffer), frames);
        }                                                                                               
                                                                                                        
        snd_pcm_close(handle);                                                                          
        return 0;                                                                                       
}