Obtaining the best quality on highly compressable movie

[DJ Alik]

Hi.

I have several questions. I would like to encode "The Others" with the maximum possible quality on 2CDs. I used DivX 5.0.3 and quality based mode with 100% quality (quant = 2) with b-frames and GMC enabled no psych. Even with original 5.1 ac3 sound the file only gets to be around 980megs. But the quality doesn't look to good. specially in the dark areas you see some macroblocking. Would any of the following solution will let me increase the quality cause I still have around 420 megs to spare for size.

1) disable GMC
2) disable b-frames
3) disable both
4) decrease key frame insertion to let's say every 200, 100, 50 frames.
5) use the new Avisynth 2.5 with mpeg2avi3 so the
color stays at YV12

waiting for any suggestions. Thank you in advance

[Teegedeck]

I'd vote for 3, 5, using a different codec ;) and perhaps a higher resolution. Keeping the original anamorphous res, you shouldn't have a problem reaching a considerably bigger filesize...

[jonny]

iirc i'd put this movie at 704x384 in 1CD, comp.test=75-80% ... with divx4.12 !!!
really dark and slow movie

You could try to use lanczos for resizing (or of course, not resizing at all :D)

[DJ Alik]

I was looking through the DVD2AVI options and noticed that in the Color Space menu there are only 2 options RGB and YUV. does that affect the way mpeg2avi3 is working?

[hakko504]

Originally posted by DJ Alik
I was looking through the DVD2AVI options and noticed that in the Color Space menu there are only 2 options RGB and YUV. does that affect the way mpeg2avi3 is working? No, the mpeg2dec3 will use YV12 as default (in A2.5). You will find a line in the .d2v that says something about colorspace, but IIRC only vfapi reads this, and vfapi will give you an error if it isn't set to RGB. All versions of mpeg2dec rightfully ignores this line.


@Tee
Hmm. I wonderwhat codec you could be referring to... maybe something reversed :rolleyes: :devil:

[OvERaCiD23]

the highest quality from DivX5 would be no b-frames, highest resolution w/o upsizing (so probably 704xXXX or 720xXXX), Lanczos resize, 1-pass QB Q2. And of course the original 5.1 AC3 included. You could also not resize during encoding (keep the anamorphic video), and resize to the correct AR during playback. A small amount of macroblocks will always exist in dark areas, and we must deal with it.

[DJ Alik]

@ OvERaCiD23
so as i understand from your post. B-Frames actually reduce the quality?!? what about GMC??

I was using Bicubic Normal resizing. What are the advantages of Lanczos?

[N_F]

B-frames give better overall quality at a given file size. But if you don't care at all about the filesize it should be disabled for absolute best quality.

Lanczos is considered to produce a sharper image than neutral bicubic.

[DJ Alik]

Ok that sounds great. One last question. Would decreasing max keyframe interval give me any better quality? Can a movie "suffer" from having too many keyframes?

[N_F]

Originally posted by DJ Alik
Ok that sounds great. One last question. Would decreasing max keyframe interval give me any better quality? Can a movie "suffer" from having too many keyframes?

Depends on whether you're using 2-pass encoding or a constant quant encoding.

Using 2-pass encodings and setting the keyframe really low will give you terrible quality. As long as you keep over 80-100 it shouldn't be any problem (personally I recommed 125, though many use 300 which is what the codec defaults to).

If you're using constant quality encoding the keyframe interval won't really affect the quality (though it might if you use a really low number like 1 or 2, but it's not worth it), only the final filesize.

[DJ Alik]

ok here are my final settings:

1 pass quality based with q = 2
Lanczos resize
B-frames off
Psych off
max interval for keyframes = 50
5.1 Ac3 sound


don't know if i should keep GMC or not?!?

i will give it a run and see what happens.

[N_F]

That should give you pretty much optimal quality.

Personally I'd leave GMC off, but the next person that answers may well say they'd leave GMC on, so it's really up to you.