Blocky artifacts only on dark scenes

[Pikoa]

On dark scenes, I get dark blocks randomly appearing at different positions. This only occurs on dark scenes. Here's my settings:-

Min Bitrate = 1800
Max Bitrate = 460
KF int = 10
Internal SCD = 96%
Space KF=100

Anti Shit =16
MinQual = 30
Motion Modulation = 50%
Curve Compression = symmetric 25%
Luminance Correction, Threshold = 10, gain = 30%
Filters: High pass=270, lowpass=2700
Bitrates redistribution = bias
Smoother = 5%
Crispiness = 26%
Gauge= 30, 35, 90%
Min-Max DRF = 2 , 5

Anybody experienced the same problem? any solution?
:confused:

[Pikoa]

Its actually dark green blocks. They look like they're floating on the screen, and not part of the scene. This only occurs on dark scenes on areas with low motion. I know it sounds like low bitrate condition, but I've increase the curve compression to 50% and its still not satisfactory (not as clean as Divx412). Any ideas?

[philippas]

If you use noise reduction filters the blocks won't be visible. Divx4 smoothes more the image thus you can't see the blocks.
Try and see if they appear on the DvD. Some DvD's are badly done.
What resize algo do you use ?
Bicubic resize(in nandub) sharpen the image, so any noise that the movie has can be seen easier.

[Pikoa]

Phillippas,

That's a thought. I used Gknot's soft Bicubic resize with additional noise reduction / smoothing (little noise setting). I'll keep that in mind in the future. Also, you're right. The source was badly encoded. Macro blocks were actually visible on the computer screen, probably not so obvious on TV. Thanks for the tip.:)