[HELP] Vapoursynth stopped working after Upgrade

[HELP] Vapoursynth stopped working after Upgrade - Printable Version

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Vapoursynth stopped working after Upgrade - Tom - 30.01.2026

Hi,
I'm new here and couldn't find a solution to my problem using the search function – so sorry if the problem is already known and solved:

I updated Hybrid from version 2025.03.09.1 to 2025.11.09.1.

Since then, Vapoursynth has stopped working (I use ‘DeSpot’ and ‘RemoveDirtMC’).

Since the update, I also get the message ‘AVX2 not detected’ when starting Hybrid, although I don't know if this has anything to do with my problem.

I use a Core i9 (Z490 chipset, Windows 11 (x64)), so AVX2 shouldn't actually be the problem...

I am grateful for any tips. Best regards,
Thomas

RE: Vapoursynth stopped working after Upgrade - Selur - 30.01.2026

That seems strange.
Hybrid uses:

bool HybridMainWindow::cpuSupportsAVX2() const

{

    unsigned int ebx = 0;

#ifdef _MSC_VER

    int cpuInfo[4];

    __cpuid(cpuInfo, 0);

    if (cpuInfo[0] < 7)

        return false;

    __cpuidex(cpuInfo, 7, 0);

    ebx = cpuInfo[1];

#elif Q_OS_WIN

    unsigned int eax, ecx, edx;

    unsigned int cpuInfo[4];

    __cpuid(0, eax, ebx, ecx, edx);

    if (eax < 7)

        return false;

    __cpuid_count(7, 0, eax, ebx, ecx, edx);

#endif

    // Bit 5 of EBX in CPUID leaf 7 subleaf 0 indicates AVX2 support

    return (ebx & (1 << 5)) != 0;

}

to check whether avx2 is supported, which seems to work fine for all my systems.
Hybrid does this check on each start.

Even if no AVX2 support was detected Vapoursynth should still work.
=> try deinstalling Hybrid before installing the new version, my guess is the switch from Vapoursynth R72 to R73 might cause problems if their files are mixed.

Cu Selur

RE: Vapoursynth stopped working after Upgrade - Tom - 30.01.2026

Hi Selur,

thank you very much for the detailed explanation and for taking the time to look into this.

Before installing the new Hybrid version, I had already uninstalled the previous one. For the time being, I will stick with the older Hybrid release that was working reliably on my system.

If you have any additional ideas, I would appreciate your thoughts on whether there is anything else I should check on my Windows installation or in other installed software that could potentially interfere with Hybrid or VapourSynth.

Thanks again for your support.

Best regards,
Thomas

RE: Vapoursynth stopped working after Upgrade - Selur - 30.01.2026

Hmm,..
a. try latest dev version
b. since Vapoursynth doesn't work, does the Vapoursynth Preview show any error?
c. does Vapoursynth not work with just one source or with any?
d. Potentially Virus Scanners or similar software could interfere with the IPC (inter process communication) or the piping.

Cu Selur

RE: Vapoursynth stopped working after Upgrade - Tom - 30.01.2026

Hi Selur,

thanks for getting back to me.

a) I have also tested the latest version as well, but I am seeing exactly the same problem.
b) The VapourSynth preview works correctly, but the processed/output video is identical to the input, as if no filtering was applied.
c) The issue occurs with different source formats, including ProRes and MPEG, so it does not seem to be tied to a specific codec or container.
d) I do not have any third-party antivirus or security software installed; I am only using the built-in Windows Defender.

I have one additional question: could there be issues caused by other Python installations that I had installed in the past but have since removed? I am wondering whether leftover files or environment variables could interfere with VapourSynth.

Also, do I need specific Microsoft Visual C++ Redistributables installed for Hybrid, or would you recommend uninstalling existing C++ redistributables and reinstalling only the required ones?

Thanks again for your help.

Best regards,
Thomas

RE: Vapoursynth stopped working after Upgrade - Selur - 30.01.2026

Hybrid does come with a portable Python install and Vapoursynth too is a portable version, so nowadays otherwise installed Python or Vapoursynth versions should not cause a problem.

Defender shouldn't cause a problem. (I made exceptions for Hybrid, the output-, the temp- and the engine-folder I use since it otherwise did slow some processing down.)

Since Vapoursynth Preview works fine that means the Vapoursynth setup itself isn't the problem.

I just did a test where I forced noAVX2 to true and then:
1. used DeSpot => encoding and preview worked fine
2. used clip MCTemporalDenoise(clip, settings="very high", ncpu=10) => encoding and Vapoursynth Preview worked
fine
3. used DeSpot + MCTemporalDenoise(clip, settings="very high", ncpu=10) => encoding and Vapoursnyth Preview worked
fine
(tried different encoders)

Does encoding work if you "enable Filtering->Vapoursynth->Misc->Always use Vapoursynth" ? (without and filters)
Does the preview work if you add filters?
Can you create and share a debug output of the job processing where the encoding doesn't work, maybe the debug output does show some hint of where the problem is.

Quote: Also, do I need specific Microsoft Visual C++ Redistributables installed for Hybrid, or would you recommend uninstalling existing C++ redistributables and reinstalling only the required ones?

I usually have a bunch of runtimes in my system, but you should get some error message about a missing dll if it were a runtime issue.

Cu Selur

RE: Vapoursynth stopped working after Upgrade - Tom - 30.01.2026

Hi Selur,

thanks for the detailed reply.

I’ll test your suggestions and report back. Before that, I want to briefly check the behavior with a fresh Windows installation to rule out any system-related issues, since this problem seems uncommon.

Could you also tell me where to find or enable the debug output in Hybrid?

I’ve been happily using Hybrid out of the box for some time now and, fortunately, never had to dig deeper into it before.

Thanks again.

Best regards,
Thomas

RE: Vapoursynth stopped working after Upgrade - Selur - 30.01.2026

Quote: Could you also tell me where to find or enable the debug output in Hybrid?

see: https://forum.selur.net/thread-3.html

RE: Vapoursynth stopped working after Upgrade - Tom - 30.01.2026

Thanks!

RE: Vapoursynth stopped working after Upgrade - Tom - 31.01.2026

Hi Selur,

just a quick update: I did a clean reinstall of Windows and then installed your latest dev/beta release. With this setup, everything is now working as expected (also AVX2 is correctly detected).

After all, I don't know what was causing the error, but to cut a long story short: thanks a lot for your tips and support.

You can close the thread from my side, as the issue is resolved.

Kind regards,
Thomas