Overall PSNR for Compare()

[temporance]

Dear AviSynth developers,

Here is a feature I'd love to see in Compare()'s logfile: Overall PSNR. When the current Compare() takes an average of frame PSNR's for its logfile, it is biased towards frames with high PSNR and will produce a higher average for sequences with very variable quality.

I wrote some more about the problems with taking the arithmetic mean of frame PSNR's here: http://forum.doom9.org/showthread.ph...413#post345413

The "Overall PSNR" treats the video seqeuence as if all video frames were tiled together into one huge image. The PSNR is effectively calculated over this huge image.

Here is a diff for Overall PSNR -- I really hope you will consider adding it as it's only a few more lines of code

PS thanks for a phenomenal tool!

--- avisynth/text-overlay.cpp	7 Jul 2003 09:10:44 -0000	1.9
+++ avisynth/text-overlay.cpp	17 Jul 2003 11:10:30 -0000
@@ -835,6 +835,8 @@
     fprintf(log,"Mean Absolute Deviation: %9.4f %9.4f %9.4f\n", MAD_min, MAD_tot/framecount, MAD_max);
     fprintf(log,"         Mean Deviation: %+9.4f %+9.4f %+9.4f\n", MD_min, MD_tot/framecount, MD_max);
     fprintf(log,"                   PSNR: %9.4f %9.4f %9.4f\n", PSNR_min, PSNR_tot/framecount, PSNR_max);
+    double PSNR_overall = 10.0 * log10(bytecount_overall * 255.0 * 255.0 / SSD_overall);
+    fprintf(log,"           Overall PSNR: %9.4f\n", PSNR_overall);
     fclose(log);
   }
   delete[] psnrs;
@@ -990,6 +992,8 @@
     MAD_min = MAD_tot = MAD_max = MAD;
     MD_min = MD_tot = MD_max = MD;
     PSNR_min = PSNR_tot = PSNR_max = PSNR;
+    bytecount_overall = double(bytecount);
+    SSD_overall = SSD;
   } else {
     MAD_min = min(MAD_min, MAD);
     MAD_tot += MAD;
@@ -1000,6 +1004,8 @@
     PSNR_min = min(PSNR_min, PSNR);
     PSNR_tot += PSNR;
     PSNR_max = max(PSNR_max, PSNR);
+    bytecount_overall += double(bytecount);
+    SSD_overall += SSD;
   }
 
   if (log) fprintf(log,"%6u  %8.4f  %+9.4f  %3d    %3d    %8.4f\n", n, MAD, MD, pos_D, neg_D, PSNR);

--- avisynth/text-overlay.h	10 Feb 2003 16:43:01 -0000	1.5
+++ avisynth/text-overlay.h	17 Jul 2003 11:10:30 -0000
@@ -177,6 +177,7 @@
   double PSNR_min, PSNR_tot, PSNR_max;
   double MAD_min, MAD_tot, MAD_max;
   double MD_min, MD_tot, MD_max;
+  double bytecount_overall, SSD_overall;
   int framecount;
 };

[sh0dan]

Thanks - I'll merge the improvement!