[FFmpeg-devel] [RFC/PATCH] fftools/ffmpeg: stop printing PSNR information in status report

[Anton Khirnov <anton@khirnov.net>]

When an encoder exports sum-of-squared-differences information in
encoded packets, print_report() will print PSNR information in the
status line. However,
* the code computing PSNR assumes 8bit 420 video and prints incorrect
  values otherwise; there are no issues on trac about this
* only a few encoders (namely aom, vpx, mpegvideo, snow) export this
  information; other often-used encoders such as libx26[45] do not
  export this, even though they could

This suggests that this feature is not useful and it is better to remove
it rather than spend effort on fixing it.
---
I needed to resolve this code's interaction with encoders as a part of
my multithreading work and spent a few hours on it. Making it work
correctly in all cases seems nontrivial and duplicates a lot of the
logic from vf_psnr.

Given that nobody ever noticed that it's broken for everything other
than YUV420P, or bothered adding support in libx264 strongly suggests to
me that nobody cares about this and it can be safely dropped.

Anyone against?
---
 fftools/ffmpeg.c | 30 ------------------------------
 1 file changed, 30 deletions(-)

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index a7e856e9e2..c73064af9a 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -767,36 +767,6 @@ static void print_report(int is_last_report, int64_t timer_start, int64_t cur_ti
             if (is_last_report)
                 av_bprintf(&buf, "L");
 
-            if (enc && (enc->flags & AV_CODEC_FLAG_PSNR) &&
-                (ost->pict_type != AV_PICTURE_TYPE_NONE || is_last_report)) {
-                int j;
-                double error, error_sum = 0;
-                double scale, scale_sum = 0;
-                double p;
-                char type[3] = { 'Y','U','V' };
-                av_bprintf(&buf, "PSNR=");
-                for (j = 0; j < 3; j++) {
-                    if (is_last_report) {
-                        error = enc->error[j];
-                        scale = enc->width * enc->height * 255.0 * 255.0 * frame_number;
-                    } else {
-                        error = ost->error[j];
-                        scale = enc->width * enc->height * 255.0 * 255.0;
-                    }
-                    if (j)
-                        scale /= 4;
-                    error_sum += error;
-                    scale_sum += scale;
-                    p = psnr(error / scale);
-                    av_bprintf(&buf, "%c:%2.2f ", type[j], p);
-                    av_bprintf(&buf_script, "stream_%d_%d_psnr_%c=%2.2f\n",
-                               ost->file_index, ost->index, type[j] | 32, p);
-                }
-                p = psnr(error_sum / scale_sum);
-                av_bprintf(&buf, "*:%2.2f ", psnr(error_sum / scale_sum));
-                av_bprintf(&buf_script, "stream_%d_%d_psnr_all=%2.2f\n",
-                           ost->file_index, ost->index, p);
-            }
             vid = 1;
         }
         /* compute min output value */
-- 
2.39.1

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