blocky x264 encode due to laczos?

[saint-francis]

I have been encoding movies with MeGUI and x264 for about 6 months or so now with a bitrate of around 1000 and using the HQ insane profile and I have noticed that some times the videos it produces are blocky; especially in black or nearly black places. I usually use the lanczos (sharp) or the lanczos4 (sharp) filter and I am wondering if the blocking could be caused by that since it is meant for use with "high" bitrates. What exactly is meant by "high bitrates"? I know that I could encode the same movie multiple times using different filters but that would take way too much time seeing as encoding a two hour movie takes me about 13-14 hours. If no one here knows though, that is what I will have to do. If so I will share my results with you all.

Thanks.

[foxyshadis]

High bitrate is roughly anything below crf/cq 20, mid bitrate is around 20-26, and low is anything above 26. (Opinions vary on where to set the goalposts, of course, and this is just mine.) You can find out where yours ended up by looking at the "final rate factor" in any logs you might have, or loading the files into avinaptic to get the average "DRF", which is roughly the same but includes b-frames. The bitrate these values give will be totally dependant on the video, so high/low "bitrate" is a misnomer in general. If you're looking for a definite quality level, use crf 22 (or 24 or whatever makes you happy, check encodes you like for good values).

It helps to remove some detail and sharpness if you don't really need it, but that's generally not the cause of the blocking you mention. Sometimes it's present in the original mpeg-2 and using mpeg2source("...",cpu=4) and/or deblock_qed can help. Sometimes it's a matter of removing noise showing up difficult-to-encode areas, you can work with AQ and deadzone to partially fix that. The AVC forum has a few threads dedicated to smooth-area-blocking.

The quickest way to fix it without testing and changing how you encode is just to play it back with ffdshow, enabling the deband filter. Shallow blocks disappear totally, though big in-motion blocks might need a noise filter.

[saint-francis]

OK. So then next step for me is to understand how to implement crf. I have read what is on the mewiki about the difference between Constant quantizer and Constant quality but I don't understand how to use these functions. Does this have to do with the Constant quantizer and Constant quality options for mode in the video configuration dialog? I have tried using the search function but apparently it's not currently working; or at least not for me.

EDIT: Forget it. I think I finally got it.

Thanks for the help.