The script's return was not a video clip

[midts]

I tested this on x32 and x64 MeGUI, but after I index this .mkv file (either FFMS or LSMASH) and click Apply Preview, I get this error:

I tested my MeGUI with other files and they work and apply preview fine except this video.

[Groucho2004]

What is wrong with this video file?

Nothing. Post the script.

[LigH.de]

The problem is not in the video file, but in the structure of the generated AviSynth script processing it.

[midts]

It's basic avs script, there's nothing special in it. And I use same exact script for other files and they work.

LoadPlugin("C:\MeGUIx64\tools\lsmash\LSMASHSource.dll")
LWLibavVideoSource("C:\sample.mkv")
LoadPlugin("C:\MeGUIx64\tools\avisynth_plugin\TIVTC.dll")
SetMemoryMax(7168)
#deinterlace
#crop
#resize
#denoise

update:
okay thats funny, preview works if I delete BOTH the

LoadPlugin("C:\MeGUIx64\tools\avisynth_plugin\TIVTC.dll")
SetMemoryMax(7168)

If I delete only one of them, it still gives the error, no matter which one I leave, but it works if you remove BOTH of them. These two lines are added into one of my default avisynth scripts. And all videos worked up until now.

[LigH.de]

As already mentioned before elsewhere: Requesting up to 7 GB (Gigabytes!) of RAM for such a basic script is nonsense, and will probably disturb other applications due to a lack of RAM left for them.

And why import a plugin which is never used with any of its provided functions?

Furthermore, sometimes the order of commands in a script is important. If you need a SetMemoryMax at all (not here, only for very complex multi-threaded scripts), use it as early as possible. And load all required plugins before using any filter.

[Groucho2004]

Your script doesn't return a clip because you added statements after the source filter. You should familiarize yourself with Avisynth grammar, particularly the "last" variable.
Besides, why do you load a plugin if you're not using it? Also, the "SetMemoryMax" statement should be at the beginning of the script (I'm just ignoring the utterly insane value you set there).

Edit - Ligh was faster.

[Groucho2004]

Here is some info on "SetMemoryMax". Although setting a high value does less harm in AVS+, you may run into problems due to paging.
You can use "SetLogParams" in AVS+ as described at the bottom of this post to determine if you need to increase the default value for SetMemoryMax for a given script.

[jagabo]

Putting SetMemoryMax() and LoadPlugin() at the start of your script is good practice -- but not strictly necessary. To clarify things a bit...

If you don't specify what to output AviSynth will output the result of the last command (comments don't count). SetMemoryMax() does not output a video clip, hence the error. LoadPlugin() will have the same problem. So you can work around the current problem by putting those two commands above LWLibAvVideoSource():

SetMemoryMax(7168)
LoadPlugin("C:\MeGUIx64\tools\lsmash\LSMASHSource.dll")
LoadPlugin("C:\MeGUIx64\tools\avisynth_plugin\TIVTC.dll")

LWLibavVideoSource("C:\sample.mkv")
#deinterlace
#crop
#resize
#denoise

Another workaround is to specify what to output -- put return(last) at the end of the script:

LoadPlugin("C:\MeGUIx64\tools\lsmash\LSMASHSource.dll")
LWLibavVideoSource("C:\sample.mkv")
LoadPlugin("C:\MeGUIx64\tools\avisynth_plugin\TIVTC.dll")
SetMemoryMax(7168)
#deinterlace
#crop
#resize
#denoise
return(last)

What is "last"? If you don't specify a name for a video stream the name "last" is used instead. So a script that reads:

SetMemoryMax(7168)
LoadPlugin("C:\MeGUIx64\tools\lsmash\LSMASHSource.dll")

LWLibavVideoSource("C:\sample.mkv")
FlipVertical()

is equivalent to:

SetMemoryMax(7168)
LoadPlugin("C:\MeGUIx64\tools\lsmash\LSMASHSource.dll")

last = LWLibavVideoSource("C:\sample.mkv")
last = FlipVertical(last)
return(last)