DCtune relevant outside of Xvid?

[dicKie]

1st post from a relative newbie, apologies if this doesn't belong here.

I see the Xvid boys are getting excited about using NASA DCtune to optimise their quantization matrices. As a CVD for stand-alone author should I be looking at this stuff too? Am I right in thinking I'm limited to defining the matrices once at the start of a sequence? Do the Xvid-ers get to redefine their matrices on the fly - like every scene change?

[MfA]

Refdivx had code which updated the matrix for each frame (I think something less computation intensive than dctune's algorithm though) but xvid should really only update at each I-frame as you say (most players will allow per frame updates, but its not standard compliant so its unlikely it will be done in future iterations of xvid). Externally you could only set them before encoding through the standard VfW interface.

I dont know how much there is to gain from tweaking the matrix for a given movie ... without some programming optimizing the inter matrix couldnt be done with something like dctune anyway, you dont have access to the error frames.