59 lines
3.8 KiB
Markdown
59 lines
3.8 KiB
Markdown
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---
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title: Motion Interpolation, 24 FPS to 60 FPS with mpv, VapourSynth and MVTools
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date: 2015-07-18
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modified: 2015-07-20
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---
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Watching videos at 60 FPS is great. It makes the video significantly smoother and much more enjoyable. Sadly, lots of movies and TV shows are still at 24 FPS. However, I recently discovered that it is actually possible to interpolate the extra frames by using motion interpolation, and convert a video from 24 FPS to 60 FPS in real time. While it is far from perfect, I think the visual artifacts are a reasonable tradeoff for high framerate.
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<!--more-->
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Firstly, what we need is mpv with VapourSynth enabled, and MVTools plugin for VapourSynth. VapourSynth must be enabled while compiling mpv. I adopted an AUR package [mpv-vapoursynth](https://aur4.archlinux.org/packages/mpv-vapoursynth/) which you can use if you are on Arch. Otherwise, all you need to do is use `--enable-vapoursynth` flag when doing `./waf --configure`. They explain the compilation on their [repository](https://github.com/mpv-player/mpv), so look into there if you are compiling yourself.
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After that, we need MVTools plugin for VapourSynth. This is available on Arch via [vapoursynth-plugin-mvtools](https://www.archlinux.org/packages/community/x86_64/vapoursynth-plugin-mvtools/), otherwise you can find their repository [here](https://github.com/dubhater/vapoursynth-mvtools). There is also a [PPA for Ubuntu](https://launchpad.net/~djcj/+archive/ubuntu/vapoursynth) where you can find `vapoursynth-extra-plugins`, but I haven't used it myself so I can't comment on it.
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After both of these are enabled, we need a script to use MVTools from VapourSynth. There is one written by Niklas Haas, which you can find here as [mvtools.vpy](https://github.com/haasn/gentoo-conf/blob/master/home/nand/.mpv/filters/mvtools.vpy). Personally, I tweaked the block sizes and precision to my liking, as well as removing the resolution limit he added. I'll put the modified version here:
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```python
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# vim: set ft=python:
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import vapoursynth as vs
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core = vs.get_core()
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clip = video_in
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dst_fps = display_fps
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# Interpolating to fps higher than 60 is too CPU-expensive, smoothmotion can handle the rest.
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while (dst_fps > 60):
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dst_fps /= 2
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# Skip interpolation for 60 Hz content
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if not (container_fps > 59):
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src_fps_num = int(container_fps * 1e8)
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src_fps_den = int(1e8)
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dst_fps_num = int(dst_fps * 1e4)
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dst_fps_den = int(1e4)
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# Needed because clip FPS is missing
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clip = core.std.AssumeFPS(clip, fpsnum = src_fps_num, fpsden = src_fps_den)
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print("Reflowing from ",src_fps_num/src_fps_den," fps to ",dst_fps_num/dst_fps_den," fps.")
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sup = core.mv.Super(clip, pel=1, hpad=8, vpad=8)
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bvec = core.mv.Analyse(sup, blksize=8, isb=True , chroma=True, search=3, searchparam=1)
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fvec = core.mv.Analyse(sup, blksize=8, isb=False, chroma=True, search=3, searchparam=1)
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clip = core.mv.BlockFPS(clip, sup, bvec, fvec, num=dst_fps_num, den=dst_fps_den, mode=3, thscd2=12)
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clip.set_output()
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```
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At this point, you should be able to try this out as suggested in the script. To set this up more permanently, I'd suggest placing this script as `~/.config/mpv/mvtools.vpy`, and also writing the following as `~/.config/mpv/mpv.conf`:
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```
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hwdec=no
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vf=vapoursynth=~/.config/mpv/mvtools.vpy
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```
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Now, whenever you open mpv, it will always use motion interpolation.
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The result is fairly good. I noticed some significant artifacts while watching anime, but it works well with movies. I'm guessing that it is harder to track the motion in animations since they are generally exaggerated.
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One thing to keep in mind, however, is performance. With `rel=2`, viewing a 1080p video results in around 90% CPU usage across all cores and 1.6 GBs of ram on my Intel i7 4700MQ. With `rel=1`, CPU usage goes down to about 60% per core. This process is very heavy on the processor, and you may have trouble unless you have a fast CPU.
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