Yesterday, 21:38
You are using Vapoursynth not Avisynth. 
And yes, the "Limit Cache"-option is basically the same. (but rarely needed)
You might want to try limiting the thread count.
Since your video is AVC, and LWLibavSource using hardware decoding ('Libav hardware decoding mode') might also help (or hurt the performance and handling of the source. (You could also try whether using DGDecNV or FFmpegSource2 does change things for you.)
En-/Disabling OpenCL and/or DFTTest2 might also change things.
Cu Selur
And yes, the "Limit Cache"-option is basically the same. (but rarely needed)
You might want to try limiting the thread count.
Since your video is AVC, and LWLibavSource using hardware decoding ('Libav hardware decoding mode') might also help (or hurt the performance and handling of the source. (You could also try whether using DGDecNV or FFmpegSource2 does change things for you.)
En-/Disabling OpenCL and/or DFTTest2 might also change things.
Cu Selur
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Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.
Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.