/* qcifpsnr.c

   this program will take two qcif files as input and calculate the PSNR based
   only on the Y component (illuminance) 

author:		Leiming Qian <lqian@uiuc.edu>
version:	1.0 alpha
date:		Jul 30th, 1999 */

#define	ROW			144
#define COL			176
#define FSIZE			38016
#define SQUARE(x)		( (x) * (x) )

#include <stdio.h>
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>

int main(int argc, char* argv[])
{
  FILE *file1, *file2;		/* input two files pointers */
  double mse, psnr;		/* mse and psnr */
  struct stat file1_status;	/* file1 status */
  struct stat file2_status;	/* file2 status */
  unsigned char buf1[FSIZE], buf2[FSIZE];
  int num_frms;
  int i, j, k;
  
  /* parse the command line */
  if (argc!=3) {
    fprintf(stderr, "Usage: qcifpsnr file1 file2\n");
    exit(1);
  }
  else {
    if ( (stat(argv[1], &file1_status)) || (stat(argv[2], &file2_status)) ) {
      fprintf(stderr, "Can't open one of the input files!\n");
      exit(2);
    }
  }

  /* get the size of these two files and open these two files */
  if (file1_status.st_size != file2_status.st_size) {
    fprintf(stderr, "Files are of different length!\n");
    exit(3);
  }
  else {
    if ( !(file1=fopen(argv[1], "rb")) || !(file2=fopen(argv[2], "rb")) ) {
      fprintf(stderr, "Can't open files for input!\n");
      exit(4);
    }
  }

  /* calculate the number of frames */
  num_frms = file1_status.st_size/FSIZE;

  /* calculate mse and psnr */
  mse = psnr = 0;
  for (i=0;i<num_frms;i++) {
    fread(buf1, sizeof(unsigned char), FSIZE, file1);
    fread(buf2, sizeof(unsigned char), FSIZE, file2);
    for (j=0;j<ROW*COL;j++)
      mse += SQUARE( (double)(buf1[j]) - (double)(buf2[j]) );
  }
  mse = mse / ROW / COL / num_frms ;
  psnr = 10.0 * log10(255*255/mse) ;

  /* print output */
  /*printf("%d frames, mse = %g, psnr = %g\n", num_frms, mse, psnr); */
  printf("%g\n", psnr);

  /* clean up */
  fclose(file1);
  fclose(file2);

  return(0);
}