Very good results : Compress H.264 to H.265 via ffmpeg, vmaf score 99.836

[Gloster]

Currently used Kubuntu 24.04. Wayland, ffmpeg 8.0

Did compress the video :

Video: h264, yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 11343 kb/s, 50 fps, 50 tbr, 90k tbn

to :
Video: hevc, yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 5075 kb/s, 50 fps, 50 tbr, 16k tbn

h.264 video-file size= 9GB. h.265 video-file size 3.7GB

VMAF score: 99.836461

the respective ffmpeg command as a script :

#!/bin/sh

for f in *.ts; do ffmpeg -y -i "$f" -map 0:v -map 0:a -vcodec libx265 -crf 16 -preset slow -vf nlmeans="1.6:7:5:3:3",unsharp="3:3:1.0" -c:a copy "$(basename "$f" .ts).mkv";done

A short description :
crf 16 = quality, less value higher quality
nlmeans = filter to reduce grain
unsharp = increase sharpness

Without the filter unsharp. I got a file size of 2.4GB (same video) and a vmaf score 95.6 .

For your information vmaf score of 100. no difference can be seen. 95.6, a good value.

Never reached this high vmaf score without "unsharp". I did decrease crf until I got a compressed file size < 1/2 source file, but the vmaf score max was 96-97.

Also I did compress with "unsharp" other videos with very equal results (vmaf score > 99.9)

I have a restriction : If I can not reduce the file size with crf 16, unsharp as given above to 1/2 of the source file-size. I decide for no compression.

Only to share my results.

Others who would like to share their results ?

[dannyboy48888]

Ah yes the fun metrics rabbit hole. Take them as a guide not concrete. I've gotten hight scores before but the background gradients etc were gone. And I've had home with a lower score (92) look fine visually as the gradients got preserved, just not exactly like the original.

[Gloster]

@dannyboy48888, yes and no. I got bad vmaf scores e.g. 55 but acceptable results checked by vivictpp or via TV.

But this case I can confirm e.g. by vivictpp, I did not see any differences in the pictures, frame by frame.
And it does not depend on the background/foreground.

And also as given by my example, I could see differences with vivictpp and the vmaf score 95, but not with a vmaf score of 99.

[Gloster]

But we have the possibility to check the "subjective" results with a respective upload :

https://we.tl/t-R2sLFzDOX9ypuf2c

The link will be for 3 days available.

From my side of view, the given webpage should be checked before to download my files.

[Gloster]

An additional hint : vmaf developed by Netflix engineers + some US-Universities + ffmpeg community to get a metric for its own, the Netflix encoding results. And if a vmaf score of > 99 would be indicate not an on top result, the logic leads to : Neither Netflix engineers nor some US-Universities nor the ffmpeg community does not know what they speak about, I must confess, I can not believe it.