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this post was submitted on 26 Oct 2024
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Asklemmy
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"15k hard" is the control h264 file
rest doesn't matter I think
but in the meantime I did some encoding to h265, and I managed to get a smaller file size however the quality sucked, so I lowered the crf and it's larger again.
In the third screenshot, preset is on 7, change that to 4. That's the speed setting - 7 is trying to do it in close to real time, 4 will take much longer but be much more efficient.
it became 504 MiB, the original was 306.
while it was doing that I tried compressing a 50Mbps clip. And I think you're gut feeling will be right, I managed to compress it with AV1 rf47 it got reduced to a 4th of it's size and it looks almost the same as the 15Mbps one. However, sadly I saw how good the raw 50Mbps one looks, so I don't think I'll go that low. Finding the sweet spot will take forever! Also isn't 50Mbps too high, the video looks amazing, but isn't that abnormally high?
If you're seeing any artifacts in the original video, you probably need to re-record in a higher bitrate. It needs to look identical to uncompressed. Your later encodes will be trying to encode all the artifacts in the original video, which could be why the file sizes keep getting bigger - you're giving it noisier video than the original.
50mbps for recording as an intermediate like that is well within the realm of normal. You can try having obs record in 264 with a quality setting instead of a bitrate setting, which can save space when things are more static - something like cq 6 or lower can do pretty well.
Unfortunately, yeah finding the sweet spot does take forever. One thing I would recommend is once you have an idea where you want to land, try a few much longer videos and see what the differences are. Slower paced sections might compress much better than the fast action stuff in one codec or another. Again it's all kind of a balancing act on where you want to be.
Oh that's a great tip, I set it to "indistinguishable" and it 3x-ed the (almost) same gameplay clip, but it does look the best so far. But if what you are saying is true, with the encoding the previous encoder's artifacts, doesn't that mean I should record in lossless?
I did try a video of my desktop doing almost nothing, and AV1 rf23 compressed it 17x. That's nice. I'll now try re-coding this "indistinguishable" h264 preset video and to record a lossless one and to re-code that as well.
From a technical level you should use something lossless in this situation, but it really quickly becomes impractical. Actually lossless 1080p60 is going to be something like 500mbps, so if you're playing for an hour I hope you have a spare 2tb drive laying around. The artifacts in really high bitrate compressed video are so minimal that they basically don't matter. Often codecs do noise removal first thing so whatever minor artifacts still exist will get smeared over by that anyway.
Also when you are testing make sure there's some movement in the video. AV1 especially has modes for presentations and things that basically make a PowerPoint, so sizes might be unrealistic if you're just recording your desktop. I don't think that gets enabled in handbrake but it's been a while since I looked.
I settled for this:
ffmpeg -i "$file" -map 0:0 -c:v libsvtav1 -preset 3 -crf 23 -maxrate 85M -map 0:a -c:a copy "${file%.mp4}-av1.mp4" -yThe files is still very large, but you can't notice any artifacts or any blurry parts, I transcode it with 7fps.