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+--- Thread: [HELP] VMAF comparison (/thread-4057.html)
VMAF comparison - ThePower - 01.04.2025
Hi I am new and I'm having trouble using Hybrid
I have a DVD that I have ripped for backup using MakeMKV. I extracted the individual episodes from the ISO into mkv files. I wanted to make 60fps QTGMC versions so that it looked more like it did when it was on a CRT TV back in the day at 60 fields/per second. So far, so good.
Step 1: Reencoded the mkvs into FFV1 with QTGMC+Bob (to make a 60fps video as losslessly as possible. I say losslessl(y) because QTGMC is running. I kept dupicates frames so i didnt have to adjust any audio/video sync issues, HDD space is plentiful.)
Step 2: Reencoded the resulting files with SVT-AV1 using preset 2 CRF 9 to get the best Quality/Time/FileSize ratio so I can stream to another device. Im okay with it being double the original 800mb file considering its double the framerate, the FFV1 would be deleted at this point and I would consider this the new "original" qtgmc copy from DVD with a VMAF above 97%.
I was wondering, am I doing this right? I wasn't sure if reencoding straight from the episode source mkv to AV1+qtgmc would allow me to skip the FFV1 encode...I guess Im confused as to "when" hybrid uses qtgmc in the encode process and whether or not it makes a difference..
Because of this I decided to do a test.
I compared the VMAF of the
(Source mkv)>(FFV1 lossless+QTGMC)>(SVT-AV1 preset 2 CRF 9) to
(Source mkv)>(SVT-AV1 preset 2 CRF 9 +QTGMC).
File sizes are 358,089,338 and 358,089,332 bytes respectively, with a VMAF of 92%.
I can't figure out why there is a file size discrepancy of 6 bytes. The file sizes are close enough I figured maybe it had to do with tags, file names, etc, and that the videos themselves were 1:1 identical. I expected a 100% VMAF score when comparing them.
No settings were changed during the AV1 encodes. The only difference is one AV1 came from a FFV1+QTGMC lossless encode of the 30fps dvd mkv file, the other came straight from the 30fps dvd mkv file using QTGMC. Shouldn't they be identical? What am I missing?
Too Long : Didn't Read:
1. Im trying to get a VMAF of >=97%, 60pFPS using qtgmc+bob, with a file size of roughly double. I have settings set so that it looks "as close as possible" to how it looked on a CRT back in the day to my well trained eye, but on modern displays.
2. Do i need to encode to FFV1 to use qtgmc first, or can i just go from source>av1+qtgmc?
3. They clearly generate different outputs, so what would be better/how to get them to be 1:1?
4. I compared two videos using VMAF and they did not come out as expected, which should have been 100%.
If anyone asks why I don't just leave them interlaced, its because interlaced looks horrible on progressive displays. The CRT's phosphor glow decay time is hard to beat and quite literally magic, which I guess is why QTGMC was created in the first place.
Sorry for the long post, and thanks for the amazing program! I cant believe it works on Linux using wine
Ill get some hate for running it that way, but getting the arch linux package and the Xsynth packages and dependacies to work is a nightmare. I tried to get it working for a week before deciding "ill just run it through wine" lol. Not to mention the buttons and layout are better on the windows version...idk why.
RE: VMAF comparison - Selur - 01.04.2025
1. VMAF between identical files often does not return 100%
2. File size differences even when remuxing the same content to mkv can be expected.
3. Encoding and filtering with multithreading often is not deterministic.
I see no need for the intermediate FFV1 file in your workflow.
Cu Selur