[Wilbert]

And yes the code probably should check for ChromaInPlacement == ChromaOutPlacement, it currently relies on the resizer core to detect a null operation however the frame will still be plane split and reassembled so cost a needless set of blits.

Ok, i see what you mean. Second attempt:

AVSValue __cdecl ConvertToYV12::Create(AVSValue args, void*, IScriptEnvironment* env)
{
  PClip clip = args[0].AsClip();
  const VideoInfo& vi = clip->GetVideoInfo();

  if (vi.IsYV12()) {
    if (!args[3].Defined() && !args[5].Defined()) || (args[3] == args[5])
      return clip;
  }

  if (vi.IsYUY2() && !args[3].Defined() && !args[4].Defined() && !args[5].Defined())  // User has not requested options, do it fast!
    return new ConvertToYV12(clip,args[1].AsBool(false),env);

  return ConvertToPlanarGeneric::CreateYV12(args,0,env);
}

@Mini-Me,

The new release has unfortunately not solved my crashes, so a question occurred to me: What's the best way to debug a crash in Avisynth?

Could you simplify your script as much as possible (retaining the crash) and post it?