Why is processed Huffyuv file so much larger than the original?

[brassplyer]

I was surprised to find that after putting a Huffyuv file through some filtering in Vdub, the processed file was a lot bigger than the original. 82 gigs vs 56 gigs.

Why is this?

[poisondeathray]

RGB vs YUY2

When you use vdub filters, most will require conversion to RGB colorspace when using "full processing mode"

If you are using avisynth filters, not vdub filters - most will allow you to stay in the same colorspace, and you can use video=>fast recompress instead of "full processing mode"