28.05.2021, 17:21
I tried that. Same problem. 
I tried loading vsViewer.exe into x64dbg. The "Failed to initialize Vapoursynth" error happens when I either "check" or "preview" the script in vsViewer. When this error comes up, the x64dbg log shows it's trying to load python39.dll. (Doesn't matter what version of vsViewer is used.)
I only tested straight output, I didn't enable any filters... I suspect that anything that needs python39.dll won't work on Windows 7. (I'm guessing straight input -> output via Vapoursynth with no filters doesn't need python39.dll.)
The Python version and dll's are built into Vapoursynth itself, so a whole build (or previous version) of Vapoursynth that uses python38.dll would be needed to make it work in Windows 7.
I have a Windows 10 machine... it works fine there, as expected.
But I still prefer Windows 7 machine as the main one. I just can't get used to Windows 10's interface. (Not to mention all the bloatware and spyware that has to be disabled.) I'm using all classic themes and mods, and the start bar that is closest to classic is SimpleClassicThemeTaskbar, and while it's workable, it's full of bugs and I'm not sure how future work on it will progress. (The current "Development build" doesn't work at all.)
(It turns out the Windows Classic Theme is still present in Windows 10 and it can be enabled with a PowerShell script, or the SimpleClassicTheme front end.)
But Windows 7 is still way more stable for classic Windows. It just can't run a lot of the latest builds of things that reply on files that can only run on a Windows 10 kernel. (Like Python 3.9 )
I tried loading vsViewer.exe into x64dbg. The "Failed to initialize Vapoursynth" error happens when I either "check" or "preview" the script in vsViewer. When this error comes up, the x64dbg log shows it's trying to load python39.dll. (Doesn't matter what version of vsViewer is used.)
I only tested straight output, I didn't enable any filters... I suspect that anything that needs python39.dll won't work on Windows 7. (I'm guessing straight input -> output via Vapoursynth with no filters doesn't need python39.dll.)
The Python version and dll's are built into Vapoursynth itself, so a whole build (or previous version) of Vapoursynth that uses python38.dll would be needed to make it work in Windows 7.
I have a Windows 10 machine... it works fine there, as expected.
But I still prefer Windows 7 machine as the main one. I just can't get used to Windows 10's interface. (Not to mention all the bloatware and spyware that has to be disabled.) I'm using all classic themes and mods, and the start bar that is closest to classic is SimpleClassicThemeTaskbar, and while it's workable, it's full of bugs and I'm not sure how future work on it will progress. (The current "Development build" doesn't work at all.)
(It turns out the Windows Classic Theme is still present in Windows 10 and it can be enabled with a PowerShell script, or the SimpleClassicTheme front end.)
But Windows 7 is still way more stable for classic Windows. It just can't run a lot of the latest builds of things that reply on files that can only run on a Windows 10 kernel. (Like Python 3.9
)