Resulting DivX *.avi file is 40% smaller than DivX Calc predicted

[cormac]

Hi,
I'm encoding 168 min. 43 sec. long movie, using DivX 4.12 codec, pass encoding, bitrate 1552, audio MP3 128 CBR in Virtual Dub 1.5.4. Although various DivX calculators predicted file size between 2 GB - 2.1 GB, resulting avi file is only 1.22 GB, so according to calculators the actually used bitrate must be around 1000.
Does anybody have any suggestion, how to fix the problem?
Thanks
Cormac

[Enchanter]

Sounds like your particular movie has reached its saturation point (where the DivX codec detected that further increase in bitrate will not result in any further increase in quality, hence the smaller-than-predicted filesize).

Regards.

[cormac]

Saturation point

Thank you for suggestion.
Still the behavior of codec looks strange. Before this movie I encoded Tora!Tora!Tora! (I specialize on war movies) with bitrate 1250. Tora was only 139 minutes long and result was 1.4 GB avi file. And resolution of video is in both cases 512*224. I'll try some tweaks tonight and report the results here. Probably the case is that there is a lot of night scenes with nearly whole screen black.
Regards
Cormac

[Enchanter]

"Probably the case is that there is a lot of night scenes with nearly whole screen black."

Clearly the reason for everything.

Perhaps the amount of action scenes is also relatively lower than the other movie, hence the lesser requirement of bits.

Regards.

[Olaa]

What can you do?

What can you do to overcome this problem?

Ola A

[Enchanter]

Increase the resolution to 640x(). That will increase the resulting filesize (though I believe it will still saturate at a point way below 2.1GB).

Seriously, you should just aim at 1.4GB instead. It will still look very good and I can assure you that it will be hard to spot, if any, quality difference with a 2.1GB file (placebo effects aside).

Cheers.

[cormac]

Night scenes resulting in smaller *.avi than predicted by calc

So, I experimented with the movie yesterday, as I promised. I picked 2 min. 50 sec. of night scene and tried to encode it with various parameters. According to calculator the resulting *.avi had to be 34 MB if I used 1552 kbits bitrate.
I tried keyframe intervals 150, 50, 25 and 12 frames. Everytime I got *.avi with size between 10 - 10.6 MB.
Then I tried to apply some filters to increase brightness of the image, so level of details in the image was little bit increased. After encoding the *.avi was almost 17 MB big.
The result is - in the very dark scenes of the movie, the resulting *.avi can be 60 to 70 percent smaller than predicted by calc, because of nature of DivX codec. The size of encoded *.avi (and also quality of night scenes) can be increased if the image is processed by bightness/contrast or levels filters to increase level of details in the dark frames.
According to this test I can say that it's possible if movie contains lot of darkness, the resulting DivX *.avi file can be pretty smaller (and dark scenes almost unviewable) than various calcs predicted.
Cormac
PS: If anyone knows, how to make dark frames brighter without "washing" briht frames, please tell me how.

[Enchanter]

I don't think you should attempt to alter the image in any way, since it will only ruin the overall picture of the movie and hence won't look good (except to satisfy your hunger for bigger filesizes). Leave it as it is.

Regards.

[cormac]

But the dark scenes are nothing but blocky mess - and some of them are the key moments of the story - for example the night retreat of British troops across the Rhine lead by Roy Urquarth.
I found some plugin to VirtualDub which allows conditional application of filters, so maybe I can work it out (http://wwwtcs.inf.tu-dresden.de/~dc1...nal/index.html)
Regards
Cormac
PS: It's not a hunger for big files - I just want to make good quality rips, so I can't accept the blocky mess on 75% of screen in the dark scenes.

[Enchanter]

Ah! Now I know why. You are using the old, lousy DivX 4.x codec!

I strongly suggest switching to the newer (and FAR better) DivX 5.x or XviD codecs. Both should satisfy you far better than the old relic you are using.

Cheers.

p.s. I am not too familiar with how well the DivX 5.x codec handles dark scenes (since I am mainly an XviD advocate and hence user), but I can assure you the XviD codec handles dark scenes very adeptly (at least I have yet to encounter problems where the XviD cannot do it).

[cormac]

Xvid vs. DivX and dark scenes

Yesterday I tried Xvid also, but saw no improvement - still blocky mess on almost whole screen.
I assume it's a nature of lossy compresion in those codecs.
I made Tora!Tora!Tora! with DivX 4.12 and result was a high quality 2 CD rip, so DivX 4.12 is fine - I think that DivX 5.x.x will produce allmost the same result.
Anyway - when I tried to install DivX 5.x.x I was unable to playback DivX video - screen was green with diagonal lines running from right to left
Cormac

[Enchanter]

"I think that DivX 5.x.x will produce allmost the same result. "

Not true.

When I upgraded from the DivX 4.12 to DivX 5.02, the significant problems I had with the old codec have been fixed, the problems being washed out colours and compression quality. Never mind the fact that the newest DivX codec still smoothens the picture like its predecessors, but overall quality has certainly been improved.

As with the same problem being reproduced with XviD, what settings were you using?

[cormac]

DivX 5.x.x - I'm unable to install it, because after instalation I can't play back my DivX movies - screen is green with lines running from upper right side to lower left side. I don't know where is the problem, but I encountered it with two different versions of DivX Pro.
XviD - i followed the guide from www.divx-digest.com, so the setting were similar like in this guide.
Cormac

[StarRide]

Yes, you're right. Most of the mpeg4 codecs have this problem of blocky black areas. Even xvid and divx.

Here is the link to a mssive xvid lumimasking / problem with blocky black areas. Some very interesting testing and results.

One very nice method to solve this problem is to use
LumaFilter() (from mpeg2dec3.dll)
and
UnFilter(-#,-#) ( - is smoothing, + is sharpening )
in avisynth 2.5.

You can also use a filter that adds noise to the dark areas, such as block buster filter.

[cormac]

Source of my problem are source VOBs

I checked the source VOB files and even in the source the night scenes are pretty blocky, so whatever codec will I use, can't make them better than they are.