Direct Streaming Avisynth Script in VirtualDUB

[Danette]

It seems that I should be able to use "Direct stream copy" in VirtualDUB (1.10.4) when using an Avisynth script. However, with every script I try, I get the VirtualDUB error message: "The source video stream uses a compression algorithm which is not compatible with AVI files". The file is an AVI file and, in fact, when I load that same file referenced in the Avisynth script into VirtualDUB, it will direct stream copy without a problem. Any ideas as to why the use of the Avisynth script fails?

[Groucho2004]

It seems that I should be able to use "Direct stream copy" in VirtualDUB (1.10.4) when using an Avisynth script.
No. VDub only "sees" the frames that Avisynth serves, it does not parse the script to gain access the original stream referenced in the script.
If you want a direct stream copy, just use the original file, it makes no sense to involve Avisynth in this case.

[Danette]

Thanks. I was hoping to use the capabilities of Avisynth, through VirtualDUB, without the re-encoding created by VirtualDUB's full processing mode.

[fvisagie]

VirtualDub's direct stream copy uses direct decompressor-to-compressor linking, i.e. video frames are not decompressed in that process. Avisynth outputs fully-decompressed frames, similarly to the way VirtualDub's full processing mode fully decompresses frames before processing (filtering etc.).