int pcm_s16le_split(const char* file, const char* out_lfile, const char* out_rfile) {
     FILE *fp = fopen(file, "rb+");
     if (fp == NULL) {
         printf("open %s failed\n", file);
         return -1;
     }
     FILE *fp1 = fopen(out_lfile, "wb+");
     if (fp1 == NULL) {
         printf("open %s failed\n", out_lfile);
         return -1;
     }
     FILE *fp2 = fopen(out_rfile, "wb+");
     if (fp2 == NULL) {
         printf("open %s failed\n", out_rfile);
         return -1;
     }
     char * sample = (char *)malloc(4);
     while(!feof(fp)) {
         fread(sample, 1, 4, fp);
         //L
         fwrite(sample, 1, 2, fp1);
         //R
         fwrite(sample + 2, 1, 2, fp2);
     }
     free(sample);
     fclose(fp);
     fclose(fp1);
     fclose(fp2);
     return 0;
 }

int pcm16le_half_volume_left( char *url ) {
    FILE *fp_in = fopen( url, "rb+" );
    if (fp_in == NULL) {
         printf("open %s failed\n", infile);
         return -1;
     }
    FILE *fp_out = fopen( "output_half_left.pcm", "wb+" );
    if (fp_out == NULL) {
         printf("open %s failed\n", outfile);
         return -1;
     }
    unsigned char *sample = ( unsigned char * )malloc(4); // 一次讀取一個sample，因為是2聲道，所以是4字節(jié) 
    while ( !feof( fp_in ) ){
        fread( sample, 1, 4, fp_in );
        short* sample_num = ( short* )sample; // 轉成左右聲道兩個short數(shù)據(jù)
        *sample_num = *sample_num / 2; // 左聲道數(shù)據(jù)減半
        fwrite( sample, 1, 2, fp_out ); // L
        fwrite( sample + 2, 1, 2, fp_out ); // R
    }
    free( sample );
    fclose( fp_in );
    fclose( fp_out );
    return 0;
}

int simplest_pcm16le_doublespeed(char *url){
    FILE *fp=fopen(url,"rb+");
    if (fp == NULL) {
         printf("open %s failed\n", file);
         return -1;
     }
    FILE *fp1=fopen("output_doublespeed.pcm","wb+");
    if (fp1 == NULL) {
         printf("open %s failed\n", outFile);
         return -1;
     }
    int cnt=0;
 
    unsigned char *sample=(unsigned char *)malloc(4);
 
    while(!feof(fp)){
 
        fread(sample,1,4,fp);
 
        if(cnt&1!=0){
            //L
            fwrite(sample,1,2,fp1);
            //R
            fwrite(sample+2,1,2,fp1);
        }
        cnt++;
    }
    printf("Sample Cnt:%d\n",cnt);
 
    free(sample);
    fclose(fp);
    fclose(fp1);
    return 0;
}