c - audio delay making it work -

i trying implement simple audio delay in c. made test delay program operated on printed sinewave , worked effectively. tried incorporating delay process in sfprocess - libsndfile- replacing sinewave inputs audio 'data' input.

i have instead of clean sample delay getting sorts of glitching , distortion.

any ideas on how correct this?

#include <stdio.h> #include </usr/local/include/sndfile.h>//libsamplerate libsamplerate //#include </usr/local/include/samplerate.h>  #define buffer_len 1024 //defines buffer length #define max_channels 2 //defines max channels   static void process_data (double *data, double*circular,int count, int numchannels, int circular_pointer );  enum {dt_progname,arg_infile,arg_outfile,arg_nargs, dt_vol};  int main (int argc, const char * argv[])//main {     static double data [buffer_len]; // buffer carries samples      double circular [44100] = {0}; // circular buffer delay     (int = 0; < 44100; i++) { circular[i] = 0; }  // 0 circular buffer      int circular_pointer = 0;          // in circular buffer      //float myvolume; // volume entered user optional 3rd argument      sndfile *infile, *outfile;     sf_info sfinfo;      int readcount;     const char *infilename = null;     const char  *outfilename = null;      if(argc < arg_nargs) {         printf("usage: %s infile outfile\n",argv[dt_progname]);         return 1;     }      //if(argc > arg_nargs) {     //       //  myvolume = argv[dt_vol];     //};     infilename = argv[arg_infile];     outfilename = argv[arg_outfile];      if (! (infile = sf_open (infilename, sfm_read, &sfinfo)))      {printf ("not able open input file %s.\n", infilename) ;         puts (sf_strerror (null)) ;         return  1 ;     };      if (! (outfile = sf_open (outfilename, sfm_write, &sfinfo)))     {   printf ("not able open output file %s.\n", outfilename) ;         puts (sf_strerror (null)) ;         return  1 ;     } ;      while ((readcount = sf_read_double (infile, data, buffer_len)))     {   process_data (data, circular, readcount, sfinfo.channels,  circular_pointer) ;         sf_write_double (outfile, data, readcount) ;     };      sf_close (infile) ;     sf_close (outfile) ;      printf("the sample rate %d\n", sfinfo.samplerate);      return 0; }   static void process_data (double *data, double *circular, int count, int numchannels, int circular_pointer) {      //int j,k;     //float vol = 1;     int playhead;     int wraparound = 10000;      float delay = 1000;  // delay time in samples      (int ind = 0; ind < buffer_len; ind++){          circular_pointer = fmod(ind,wraparound);     // wrap around pointer         circular[circular_pointer] = data[ind];           playhead = fmod(ind-delay, wraparound);     // read delayed signal          data[ind] = circular[playhead];            // output delayed signal          circular[ind] = data[ind];   // write incoming signal     };       //volume     /*for (j=0; j<numchannels; j++) {         (k=0; k<count; k++){              data[k] = data[k]*-vol;*/          //}printf ("the volume %f", vol);      return; } 

at least 1 problem pass circular_pointer value, not reference. when update in function, it's same value next time call function.

i think on right track, here, if want that's structured bit better, might want checkout answer:

how add echo effect on audio file using objective-c