Hello again,
Well, after so much trying and spending long hours on test encodes and after watching both encodes (LUMI and NOLUMI) very carefully, I would like to comment a bit on the results.
First of all, it is very clear that using lumi masking in both passes is very helpful in terms of increasing compressibility (LUMI: 54.20%, NOLUMI: 51.84%) and in terms of reaching lower quantizers (obviously more 2 and 3 quantizers) for the movie.
Secondly, comparing the two encodes frame by frame and judging by (only) the screenshots (of the darkest and most likely-to-be-problematic scenes) would be absolutely misleading (after all, you can't see much difference, can you?
), since when you watch and compare the two encodes (using ffdshow and of course choosing "decode using XviD" in the codecs tab and selecting "IDCT: XviD" in the Miscallenous tab), you can't spot any quality loss or artifacts in the "both passes LUMI" encode.
Next, the settings used in the first and second passes and the AltCC parameters (suggested by Koepi) really seem to work fine and both encodes (LUMI/NOLUMI) are really impressing and of pretty high quality
.
Finally, of course I choose to keep the "both passes LUMI" encode for my 1cd rip (with 0.100q ogg) of this movie. And my vote is now (with much more certainty) for
"lumi masking in both passes" .
best regards to all,
iago