Using mvfile with nth pass...

[BluDChyLD]

Hey,
I've always used the mvfile to speed up my encodes, but now i've read that is can degrade quality by messing with DivX's motion estimation between passes. I only do 2 pass encodes (first pass, nth pass) so is it ok to use?
Thanks

[BluDChyLD]

I also read that using b-frames automatically disables the mvfile being used. Is this true?

[jggimi]

http://www.divx.com/support/guides/DivXGuide51.pdf Page 44: MV re-use can offer reduced encoding time under Standard Performance Quality mode, but marginally reduces video quality.

Where time is not a priority best results are seen when no MV re-use is enabled.

MV re-use has less significant effect on encoding duration when bi-directional encoding is enabled.

[BluDChyLD]

does it degrade the quality by much?

[jggimi]

Why not test it yourself, and see? Quality is often subjective. Take a small sample, encode at the resolution and bitrate that you would use for the complete work, and encode it twice: once with the feature, once without.

Personally, I don't use it, because 1) I use B-Frames, and 2) encoding time is not critical for me.

[BluDChyLD]

hmmm... Just did a test using a clip for 21 grams, and I can't see much differance at all!

It's a bit difficult to judge quality viewing the clips consequentively, is there any way I can view them side by side?

[stephanV]

avisynth script could do it:
clip1 = avisource ("c:\video1.avi")
clip2 = avisource ("c:\video2.avi")
stackhorizontal (clip1,clip2)

open script in player and compare :)

('stackvertical' might be a better choice though, in respect with your screen dimensions)

[BluDChyLD]

thanks for the avisynth file, very useful :) Even with a frame by frame comparison I can see very little difference, but I might aswell keep it off to be on the safe side.