I found that the features were lacking and the official DivX guide, as well, which doesn't mention Noise Reduction. Is there no way to add your own Quantization Matrix? There's not much to tweak if you're not 100% satisfied with your output. Always seemed like DivX GUI was aimed at someone who never encoded video before. Maybe someone knows something I don't.

if you wanna "tweak" use xvid. in divx there are no ways to use custom quant matrix though, also mpeg quantization is still buggy.

MPEG quant is fixed in 6.1.1, noise reduction is covered on page 62 of the guide under "Source preprocessing". Sharktooth is correct in that custom quant matrices are not supported.

sorry i got confused about mpeg quant. last time i tried it it was b0rked and i thought it was with 6.1.1.