Some numbers:
Source: SVCD 480x480 (sorry I currently have no DVD material)
Processor: Athlon 500 non-DDR memory.
AVS2AVI -> XviD "null encoder".
Code:
77.63% mpeg2dec3.dll
11.52% avisynth.dll
That's about what can be expected overhead.
Distribution within mpeg2dec3.dll
Code:
16.13% SSEMMX_IDCT
11.79% CMPEG2Decoder::Copyall
10.53% CMPEG2Decoder::decode_macroblock
4.68% CMPEG2Decoder::motion_compensation
3.84% CMPEG2Decoder::Copyodd
2.66% MC_put_16_mmxext
2.55% CMPEG2Decoder::Show_Bits
Copyall is a bit suspicious. Either there are a LOT of copying going on, or there is some inefficiencies. Block prefetching/movntq might be worth trying out. I'll try replacing it with a bitblit.