The only problem with this PR/diff is that it creates just a avfilter wrapper around whisper.cpp library and requires the user to manage the dependencies on their own. This is not helpful for novice users who will first need to:

1. git clone whisper.cpp

2. Make sure they have all dependencies for `that` library

3. Hope the build passes

4. Download the actual model

AND only then be able to use `-af "whisper=model...` filter.

If they try to use the filter without all the prereqs they'll fail and it'll create frustration.

It'd be better to natively create a Whisper avfilter and only require the user to download the model -- I feel like this would streamline the whole process and actually make people use it much more.

While that would be nicer from an end-user perspective, it's something hard to maintain for FFmpeg itself. Consider the velocity of the whisper-cpp project. I'm sure that – just like with filters such as vmaf, which also require building a dependency and downloading a model – precompiled versions will become available for novice users to directly download. Especially considering whisper-cpp is MIT-licensed.