[FFmpeg-devel] [PATCH v3 2/2] libavformat/vapoursynth: Update to API version 4, load library at runtime

[Stefan Oltmanns]

Am 23.08.24 um 14:25 schrieb Ramiro Polla:
>
> I finally managed to test the patches on a real Windows system.
>
> They both look good to me, I'll apply them in a couple of days if
> there are no other comments.
>
> It would be helpful to write a page in the trac wiki with a basic
> howto and common pitfalls. I had problems installing python and
> vapoursynth for my user only, and then for all users on the Windows
> machine. I had to uninstall everything, remove some registry keys, and
> try again using administrator to install to all users. I also had to
> manually install Microsoft Visual C++ Redistributable. There was no
> good error message telling me what was going wrong. When I added an
> av_log() with FormatMessage() after LoadLibraryW() failed, the error
> message was also unhelpful.

Just to make that clear: You had problem installing Python/VapourSynth
on Windows, not with the patch? I know Python can be somewhat
problematic on Windows from other contexts, but VapourSynth is usually
straight forward.

The install guide for VapourSynth lists some problems you may have
experienced:

http://www.vapoursynth.com/doc/installation.html#windows-installation

-Both Python and VapourSynth must be installed as either current user or
all users/system
-On current user installs it cannot install the required Microsoft
Visual C++ Redistributable

To ensure installation of VapourSynth worked you can run "vspipe -v",
this will show the installed version if it's working or an error message
if not.

Common issue on Linux/macOS is that the Python package cannot be found,
you have to set PYTHONPATH for example like this:
PYTHONPATH=/usr/local/lib/python3.12/site-packages
ffmpeg will display the PYTHONPATH issue as a possible problem if can
find the vapoursynth library, but not initialize it.

On recent versions of macOS, it will not look for libraries in
/usr/local/lib anymore, you may have to set
DYLD_LIBRARY_PATH=/usr/local/lib

Best regards
Stefan