Avisynth preview error

[Selur]

Hybrid uses 32bit Avisynth+ which is restricted in how much memory it uses.
Since switching to Avisynth+ 64bit would mean dropping support for:

• AGC.dll <- HDRAG AGC (High Dynamic Range Automatic Gain Control) https://forum.doom9.org/showthread.php?t=93571
  
• amDCT.dll <- amDCT (adaptive multipurpose DCT video filter) https://sites.google.com/site/amdctfilter/
  
• asharp.dll <- aSharp http://www.avisynth.nl/users/warpenterpr...030118.zip
  
• assrender.dll <- AssRender https://forum.doom9.org/showthread.php?t=148926
  
• BucketMedian.dll <- BucketMedian https://github.com/chikuzen/BucketMedian/
  
• channelmixer.dll <- Channel Mixer http://avisynth.nl/index.php/ChannelMixer
  
• ColorBalance.dll <- Color Balance https://forum.doom9.org/showthread.php?t=139361
  
• deblock_pp7.dll <- MPlayer PP7 Deblocking https://forum.doom9.org/showthread.php?t=172498
  
• Decrawl.dll <- DeCrawl http://avisynth.nl/index.php/DeCrawl
  
• Deen.dll && deen1b1.dll <- Deen http://avisynth.nl/index.php/Deen (Deen.dll used in EdgeCleaner)
  
• DeVeed.dll <- DeVeed http://www.avisynth.nl/users/warpenterpr...061226.zip
  
• FanFilter.dll <- FanFilter http://www.avisynth.nl/users/vcmohan/Fan...er_src.zip
  
• frfun7.dll <- FrFun7 http://avisynth.nl/index.php/Frfun7
  
• ImageSequence.dll <- ImageSequence (http://avisynth.nl/index.php/ImageSequence) (I use this in Logo.avs)
  
• LoadPluginEx.dll <- LoadPluginEx http://avisynth.nl/index.php/LoadOldPlugins (I use this to use PeachSmoother)
  
• medianblur.dll <- MedianBlur https://forum.doom9.org/showthread.php?t=84636 (I need this for SuperToon.avs)
  
• Motion_12Dec05.dll <- I need this for SalFps3 (http://avisynth.nl/index.php/SalFPS3)
  
• NLMeansCL2.dll <- okay, I can drop this one for KNLMeansCL
  
• nnedi.dll <- NNEDI https://forum.doom9.org/showthread.php?t=147695 (QTGMC dependency)
  
• nnedi2.dll <- NNEDI2 https://forum.doom9.org/showthread.php?t=147695 (QTGMC dependency)
  
• NoiseGenerator.dll <- Noise Generator http://www.avisynth.nl/index.php/NoiseGenerator
  
• PeachSmoother.dll <- PeachSmoother https://www.avisynth.org.ru/docs/english...oother.htm
  
• QTSource.dll <- QT Source http://www.avisynth.nl/index.php/QTSource (used to read pseudo MXF structure with a .mov pointer file)
  
• Toon-v1.1.dll <- Toon http://avisynth.nl/index.php/Toon
  
• unblock.dll <- UnBlock https://avisynth.org.ru/unblock/unblock.html
  
• UnFilter.dll <- UnFilter http://avisynth.nl/index.php/UnFilter
  
• Waifu2xAvisynth.dll <- Waifu2x https://github.com/sunnyone/Waifu2xAvisynth
  
• warpsharp.dll <- WarSharp http://www.avisynth.nl/index.php/WarpSharp (for LimitedSharpenFaster with Smode=1)
  

see: https://forum.doom9.org/showthread.php?t=181022
I have no plan to switching to 64bit Avisynth.

Looking at your script:

ClearAutoloadDirs()
LoadCPlugin("C:\PROGRA~1\Hybrid\32bit\AVISYN~1\ffms2.dll")
LoadPlugin("C:\PROGRA~1\Hybrid\32bit\AVISYN~1\despot.dll")
SetFilterMTMode("DEFAULT_MT_MODE", MT_MULTI_INSTANCE)
# loading source: I:\!_Video\704.mp4
#  input color sampling YV12@8, matrix:Rec.709
#  input luminance scale tv
Source = FFVideoSource("I:\!_Video\704.mp4",cachefile="C:\Windows\Temp\mp4_d0e32cc26616a0761a8b137f28dbba5d_853323747_1_0.ffindex",fpsnum=30,colorspace="YV12")
# cutting from 0 with 42722 frames - WARNING: This might cause synch issues
Source = Source.Trim(0, 42722)
# current resolution: 3840x2160
# filtering
# despotting using DeSpot
SourceFiltered = Source
SourceFiltered = SourceFiltered.DeSpot(median=false,p2=22,seg=2,mheight=15,interlaced=false)
# stacking horizontal for filter preview
# adjust color to RGB32
SourceFiltered = SourceFiltered.ConvertToRGB32(matrix="Rec709")
Source = Source.ConvertToRGB32(matrix="Rec709")
StackHorizontal(Source, SourceFiltered)
PreFetch(6)
return last

the only real way I see to lower the memory consumption would be to:
a. enable 'Filtering->Avisynth->Misc->Miscellaneous->AvisynthPlus limit memory' and try different values for 'Memory max'
b. use a lower MT-Thread count by setting 'Filtering->Avisynth->Misc->Miscellaneous->MT-Threads' to a value like 2 and if that does not help use 'Disable MT' to disable threading through Avisynth (filters itself might still use threading)
If the source&filter combination you chose (4k video + DeSpot) still crashes with, I can only advice to either try using Vapoursynth or look for another tool than Hybrid.

Cu Selur