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Old 27th July 2018, 15:13   #78  |  Link
poisondeathray
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Join Date: Sep 2007
Posts: 5,340
Quote:
Originally Posted by bradwiggo View Post
I had changed the CRF settings a while ago in meGUI, I has the crf at 6 and the preset set to slower. I noticed this today and changed it back to 9.5 and medium, and then interpolated a small (2 minute long) video. The interpolation approximately doubled the file size. I then started to interpolate a larger (1 hour) file, and megui was reporting that the output file would be almost 4 times the size of the original. Why is this the case, as I am using the exact same settings for each of those two?

Also, as seen as I am interpolating 24fps to 60fps, does that mean the file size of the output should be at least 2.5 times that of the input to stop quality loss, or does it not necessarily work like that?

CRF doesn't necessarily work like that, and strictly speaking it's not a measure of "quality" ; it's just a rate control method

2.5x the number of frames generated by interpolation usually does not result in 2.5x the bitrate at a given CRF (everything else the same) ; because a) the relationship is not linear and b) the interpolated frames are usually more blurry and lower quality. When you do get much higher bitrate at a CRF value, it's usually indirect evidence that your have more interpolation artifacts than normal. Ugly edge morphing artifacts tend to "eat up" more bitrate, than a clean smooth interpolation. ie. The less differences between frames, the less bitrate at a given CRF value; roughly speaking - it's the differences between frames that are stored. The more differences, the more bitrate
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