That's quite cool. I guess ffmpeg would kind of technically be a replacement for avisynth at this point.

Still, I find the syntax it uses horrible:

  ffmpeg -an -ss 12 -t 3 -i bigbuckbunny.mov -vf 'crop=iw-1, drawvg=file=progress.vgs, format=yuv420p' -c:v libvpx-vp9 output.webm

I understand that most of this comes from simplicity of use from the shell, so if you take this point of view, the above makes a lot of sense.

My poor, feeble brain, though, has a hard time deducing all of this. Yes, I can kind of know what it does to some extent ... start at 12 seconds right? during 3 seconds ... apply the specified filter in the specified format, use libvpx-vp9 as the video codec ... but the above example is somewhat simple. There are total monsters in actual use when it comes to the filter subsystem in ffmpeg. Avisynth was fairly easy on my brain; ffmpeg does not, and nobody among the ffmpeg dev team seems to think that complicated uses are an issue. I even wrote a small ruby script that expands shortcut options as above, into the corresponding long names, simply because the long names are a bit easier to remember. Even that fails when it comes to complex filters used.

It's a shame because ffmpeg is otherwise really great.