c 언어 ALSA 녹음 실현

c 로 ALSA 녹음 과 재생 을 실현 합 니 다.
c 언어 ALSA 재생 실현
이것 은 비교적 간단 하기 때문에, 직접 코드 를 올 립 니 다.

#include 
#include 
#include 

#define CHANNELS 2
#define FSIZE 2*CHANNELS

int main()
{
    int fd;
    
    char *out_filename="output.raw";
    char *file=out_filename;
    fd = open(file,O_WRONLY|O_CREAT,0777);
	if( fd ==-1)
	{
		printf("open file:%s fail.
",out_filename);
		exit(1);
	}
	
    int ret=0;
    
    snd_pcm_t *handle;
    //         
    ret = snd_pcm_open(&handle, "default",SND_PCM_STREAM_CAPTURE, 0);
	if (ret < 0) 
	{
		printf("unable to open pcm device!
");
		exit(1);
	}
	
	//         
    snd_pcm_hw_params_t *params;
    //params    
    snd_pcm_hw_params_malloc(&params);
    //  pcm     hwparams
    ret=snd_pcm_hw_params_any(handle, params);
	if (ret < 0) 
	{
		printf("Can not configure this PCM device!
");
		exit(1);
	}
	
	//       buffer      
	//SND_PCM_ACCESS_RW_INTERLEAVED    (period)           
	ret=snd_pcm_hw_params_set_access(handle, params,SND_PCM_ACCESS_RW_INTERLEAVED);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to interleaved!
");
		exit(1);
	}
	
	//  16     
	ret=snd_pcm_hw_params_set_format(handle, params,SND_PCM_FORMAT_S16_LE);
	if (ret < 0) 
	{
        printf("Failed to set PCM device to 16-bit signed PCM
");
		exit(1);
	}
	
	//     
	ret=snd_pcm_hw_params_set_channels(handle, params, CHANNELS);
	if (ret < 0) 
	{
        printf("Failed to set PCM device CHANNELS
");
		exit(1);
	}
	
	unsigned int val=48000;
	int dir;
	//     ,        ，             
	ret=snd_pcm_hw_params_set_rate_near(handle, params,&val, &dir);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to sample rate
");
		exit(1);
	}
	
	unsigned int buffer_time,period_time;
	//         ,buffer_time   us,500000us=0.5s
	snd_pcm_hw_params_get_buffer_time_max(params, &buffer_time, 0);
	//printf("buffer_time:%d
",buffer_time);
	if ( buffer_time >500000)
		buffer_time = 500000;
	
	//      
	ret = snd_pcm_hw_params_set_buffer_time_near(handle, params, &buffer_time, 0);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to sample rate
");
		exit(1);
	}
	//      
	period_time = 26315;
	ret = snd_pcm_hw_params_set_period_time_near(handle, params, &period_time, 0);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to period time
");
		exit(1);
	}
	
	//        PCM  
	ret = snd_pcm_hw_params(handle, params);
	if (ret < 0) 
	{
		printf("unable to set hw parameters
");
		exit(1);
	}
	
	snd_pcm_uframes_t frames;
	snd_pcm_hw_params_get_period_size(params,&frames, &dir);
	printf("period_size:%ld
",frames);
	int size;
	// 1 frame = channels * sample_size.
	size = frames * FSIZE; /* 2 bytes/sample, 1 channels */
	printf("size:%d
",size);
	char *buffer;
	buffer = (char *) malloc(size);
	  
    struct timeval start, end;
    gettimeofday( &start, NULL );
	while (1) 
	{
		ret = snd_pcm_readi(handle, buffer, frames);

		if (ret == -EPIPE) {
		// EPIPE means overrun 
			fprintf(stderr, "overrun occurred
");
			ret=snd_pcm_prepare(handle);
			if(ret <0){
				printf("Failed to recover form overrun");
				exit(1);
			}
		}
		else if (ret < 0) {
			fprintf(stderr,"error from read: %s
",snd_strerror(ret));
			exit(1);
		} 
		else if (ret != (int)frames) {
			fprintf(stderr, "short read, read %d frames
", ret);
		
		}
		
		ret = write(fd, buffer, size);
		if (ret <0){
			perror("fail to write to audio file
");
		}

        gettimeofday( &end, NULL );
        printf("%ld",end.tv_sec-start.tv_sec);
        printf("\r\033[k");
        fflush(stdout); 
	}
    
	close(fd);
	snd_pcm_drain(handle);
	snd_pcm_close(handle);
	free(buffer);
	
    return 0;
}

//    
int volume_adjust(char *in_buf,float vol)
{
    short buf=0;
    buf=*in_buf+(*(in_buf+1)<<8);
    
    if(buf>=-1&&buf<=1)
    {
        buf=0;
    }
    
    buf=buf*vol;
    
    
    if(buf>=32767)
    {
        buf=0;
        *in_buf=(char)buf;
        *(in_buf+1)=buf>>8;
    }
    else if(buf<=-32768)
    {
        buf=0;
        *in_buf=(char)buf;
        *(in_buf+1)=buf>>8;
    }
    else
    {
        *in_buf=(char)buf;
        *(in_buf+1)=buf>>8;
    }
    return 0;
}

컴 파일

gcc alsa_record.c -o alsa_record -lasound