分离PCM16LE双声道音频

PCM16LE中左右声道是间隔存储的。16表示采样位数是16bit，LE表示Litter Endian，小端模式。

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int pcm16leSplit(const char * url){
    FILE *fp=fopen("","wb+");
    FILE *fp1=fopen("","wb+");
    FILE *fp2=fopen(url,"rb+");
    
    unsigned char *temp=(unsigned char *)malloc(4);
    
    while(!feof(fp2)){
        fread(temp,1,4,fp2);
        
    	fwrite(temp,1,2,fp);
        fwrite(temp+2,1,2,fp1);
    }
    free(temp);
    fclose(fp);
    fclose(fp1);
    fclose(fp2);
    
    return 0;
}

左声道音量减半

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int pcm16leCutLeft(char *url){
    FILE *fp=fopen("","wb+");
    FILE *fp2=fopen(url,"rb+");
    
    unsigned char *temp=(unsigned char *)malloc(4);
    
    while(!feof(fp2)){
        fread(temp,1,4,fp2);
        
        short *sh=(short *)temp;
        *sh=(*sh)/2;
        
    	fwrite(temp,1,2,fp);
        fwrite(temp+2,1,2,fp);
    }
    free(temp);
    fclose(fp);
    fclose(fp2);
    
    return 0;
}

PCM16LE2PCM8

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//将-32768~32767转换为0~255
int pcm16le2pcm8(char *url){
    FILE *fp=fopen("","wb+");
    FILE *fp2=fopen(url,"rb+");
    
    unsigned char *temp=(unsigned char *)malloc(4);
    while(!feof(fp2)){
        fread(temp,1,4,fp2);
        
        char pcm8;
        pcm8= (*(short*)temp)>>256+128;
    	fwrite(&pcm8,1,1,fp);
        
        pcm8= (*(short*)(temp+2)>>256+128;
        fwrite(&pcm8,1,1,fp);
    }
    free(temp);
    fclose(fp);
    fclose(fp2);
               
    return 0;
}

PCM16LE2WAVE

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WAVE是微软上常见的音频格式，具体为在PCM前加了一个文件头
WAVE_HEADER
WAVE_FMT
WAVE_DATA
PCM数据 
;
typedef struct WAVE_HEADER{  
		char         fccID[4];        
		unsigned   long    dwSize;            
		char         fccType[4];    
}WAVE_HEADER;  
 
typedef struct WAVE_FMT{  
		char         fccID[4];        
		unsigned   long       dwSize;            
		unsigned   short     wFormatTag;    
		unsigned   short     wChannels;  
		unsigned   long       dwSamplesPerSec;  
		unsigned   long       dwAvgBytesPerSec;  
		unsigned   short     wBlockAlign;  
		unsigned   short     uiBitsPerSample;  
}WAVE_FMT;  
 
typedef struct WAVE_DATA{  
		char       fccID[4];          
		unsigned long dwSize;              
}WAVE_DATA; 

int pcm16le2wave(const char *pcmUrl,int channels,int sample_rate/*44100*/,const char * waveUrl){
    int bits=16;
    unsigned   short   m_pcmData;
    WAVE_HEADER   pcmHEADER;  
    WAVE_FMT   pcmFMT;  
    WAVE_DATA   pcmDATA; 
    FILE *fp=fopen(pcmUrl,"rb+");
    FILE *fp2=fopen(waveUrl,"wb+");
    
    memcpy(pcmHEADER.fccID,"RIFF",strlen("RIFF"));                    
    memcpy(pcmHEADER.fccType,"WAVE",strlen("WAVE"));
    fseek(fp2,sizeof(WAVE_HEADER),1);
    
    pcmFMT.dwSamplesPerSec=sample_rate;  
    pcmFMT.dwAvgBytesPerSec=pcmFMT.dwSamplesPerSec*sizeof(m_pcmData);  
    pcmFMT.uiBitsPerSample=bits;
    memcpy(pcmFMT.fccID,"fmt ",strlen("fmt "));  
    pcmFMT.dwSize=16;  
    pcmFMT.wBlockAlign=2;  
    pcmFMT.wChannels=channels;  
    pcmFMT.wFormatTag=1;  
 
    fwrite(&pcmFMT,sizeof(WAVE_FMT),1,fp2);
    
    memcpy(pcmDATA.fccID,"data",strlen("data"));  
    pcmDATA.dwSize=0;
    fseek(fp2,sizeof(WAVE_DATA),SEEK_CUR);
    
    fread(&m_pcmData,sizeof(unsigned short),1,fp);
    while(!feof(fp)){  
        pcmDATA.dwSize+=2;
        fwrite(&m_pcmData,sizeof(unsigned short),1,fp2);
        fread(&m_pcmData,sizeof(unsigned short),1,fp);
    }
    
    pcmHEADER.dwSize=44+pcmDATA.dwSize;//44没说是啥 应该是文件头
 
    rewind(fp2);
    fwrite(&pcmHEADER,sizeof(WAVE_HEADER),1,fp2);
    fseek(fp2,sizeof(WAVE_FMT),SEEK_CUR);
    fwrite(&pcmDATA,sizeof(WAVE_DATA),1,fp2);
	
	fclose(fp);
    fclose(fp2);
 
    return 0;
}