what's the purpose of "Fast compression" under VDM ?

[adrianmak]

as title........

[FlimsyFeet]

VirtualDub filters only work in RGB colour space. So if you want to use Full Processing Mode, and your source has YUY2 or YV12 colour space, VirtualDub has to convert to RGB first.

If you just want to compress encode something without any colour space conversions, you can use Fast Recompress.

[Eric B]

Someone using avisynth and its plugins (none of VirtualDub) can always use "Fast Recompress", cannot he?

[communist]

Someone using avisynth and its plugins (none of VirtualDub) can always use "Fast Recompress", cannot he?
Yes you can, unless you're using a codec which cant handle the colorspace you're delivering via Avisynth. VirtualDub will then throw an error telling you to switch to full processing or slow repack, though its better to do colorspace conversions in Avisynth and fall back to Fast Repack.

For ex. if Codec X only accepts RGB just add ConvertToRGB32() to your script and select Fast Repack.