FFTW on real data sequence

问题

I'm reading a raw sound file, and I' m trying to run the fft on it, with aim of getting the PSD at the end, but I'm in the start and I get an error that I can't understand, hope getting some help here, the code is:

#include <stdio.h>
#include <fftw3.h>

int main(){
    char* fileName = "sound.raw";
    FILE* inp = NULL;
double* data = NULL;
int index = 0;
fftw_plan  plan;
fftw_complex* out; 
double r,i;
int N = 8192;

//Allocating the memory for the input data 

data = (double*) fftw_malloc(sizeof(double)*N);
out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex)*N);
plan = fftw_plan_dft_r2c_1d(N,data,out,FFTW_FORWARD);
// opening the file for reading 
inp = fopen(fileName,"rb");
if(inp== NULL){
    printf(" couldn't open the file  \n ");
    return -1;
}
while(!feof(inp)){
    printf( " index  %d",index); // just  get where the program crashs 
        if(index < N){
            fread(&data[index],sizeof(short),1,inp); 
            index = index +1;
        }
        else{
            index = 0;
            fftw_execute(plan);
            printf("New Plan \n");
            printf(" Real \t imag \t Magn \t  \n");
            for(index = 0 ; index<N; index++){
                r=out[index][0];
                i =out[index][1];
                printf("%lf \t %lf \t %lf \t \n",r,i,index);
            }
            index = 0 ;
        }
}
return 0 ; 
}

the program crashes when the index = 8106 and I'm sure that file contain more data. the error that I get is:

Segmentation fault (core dumped )

I know that the error is related to pointer trying to access a memory that it's not allowed to , my question is how can I solve this!

UPDATE

I checked the program again and the error is exactly in line :

fftw_execute(plan) ;

I hope helps more !

thanks in advance!

回答1:

Found it , the error was in the paramter given to the plan function :

plan = fftw_plan_dft_r2c_1d(N,data,out,FFTW_FORWARD); //

should be instead

plan = fftw_plan_dft_r2c_1d(N,data,out,FFTW_MEASURE);

plan = fftw_plan_dft_r2c_1d(N,data,out,FFTW_ESTIMATE);

since the direction of the transformation is implicit in the function's name !

thanks anyway !

来源：https://stackoverflow.com/questions/24139974/fftw-on-real-data-sequence

标签

signal-processing

fftw