AviSynth vs AviSynth+ vs VapourSynth: which one should I choose?

Question

AviSynth is an old-but-still-useful tool for processing video via script, but I’ve noticed that there is a fork called AviSynth+ that appears to have some improvements. And then there’s VapourSynth rewritten to use Python.

What are the pros and cons of these versions?

For use-cases such as QTGMC deinterlacing and high-quality resizing, is one clearly better than the other?

Answer 1

There is no reason to use old, obsolete AviSynth — “old-but-still-useful” are almost all programs, but why to complicate your life with old, unsupported versions of them?

Every script for AviSynth works well in the AviSynth+, so even if you know AviSynth, there is nothing to relearn. The opposite is not true, however.

Use AviSynth+ (pros: all, cons: none), particularly pinterf/AviSynthPlus (forked from already dead AviSynth/AviSynthPlus).

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Note:

The other situation is with GUI programs — if the old version satisfied you and the new one is too complicated, with changed menus, new icons, colors etc.

But it is not the case of AviSynth+ — you don't “see” the new commands, functions or parameters, so they don't disturb you.

Answer 2

As a summary of the differences:

AviSynth

• Outdated and no longer recommended for use
• Only available in 32bit – not able to use 64bit plugins/filters
• No multi-threading (unless you install AviSynth-MT, another fork, which is prone to errors and issues and no updates over last 4+ years)
• Older and only supports 8bit video
• Lacks support for some color spaces (YV16, YV24 etc.)
• Latest release over 4 years ago (May 2016)

AviSynth+

• Has both a 32bit and 64bit version, although the 32bit version apparently has some issues
• Supports multi-threading which can significantly improve rendering performance for some functions (similar to AviSynth-MT, another fork, but AviSynth+’s appears more stable)
• Be aware that using the 64bit version will require all plugins and filters to also be 64bit – and not all of them have 64bit versions. There are some filters that are 64bit only, however, which means you’re able to use those.
• QTGMC runs faster in multi-threaded mode, and also apparently in 64bit mode
• AviSynth+ specific documentation is limited, but most of the great AviSynth wiki also applies to AviSynth+ and many pages now have notes mentioning any specific instructions for working with AviSynth+.
• Also runs on Linux, which is useful when you need to run it on a server
• Regularly updated, with latest release Jun 2020

Note: be sure to get a recent version of AviSynth+ from https://github.com/AviSynth/AviSynthPlus/releases. There was a pinterf fork and it has been merged back to upstream.

Or you can use the Universal AviSynth Installer which allows you to easily switch between the different versions of AviSynth, AviSynth-MT, and AviSynth+ (32bit and 64bit).

VapourSynth

• Rewritten to use Python, a much more powerful and flexible scripting language
• Multi-threaded
• Supports generalized colorspaces whereby new or custom colorspaces can be specified at runtime
• Also runs on Linux, which is useful when you need to run it on a server
• Documentation isn't as detailed as AviSynth (it's not a community wiki)
• Regularly updated, with latest release Aug 2020