x264 CQP vs 2pass ABR (at similar bitrates)

[GradationAir]

Assuming they land on the same size, which one has superior quality? Should be same?

[Hikmet]

If you want use Constant Quality, then never use "MB-Tree", because dark areas will encode bad.

I encode tutorial videos with x264 Constant Quality = 30 and file size be small and quality is acceptable. If tutorial video is screencast, then decrease FPS to 10 and file size be smallest. Use "CABAC" and don't use "P4x4" macroblocks. "B-Frame = 3" or "4".

If you will encode film, then use 2-pass and use "MB-Tree" and "CABAC" and don't use "P4x4" macroblocks. "B-Frame = 3" or "4".

[jagabo]

If you want use Constant Quality, then never use "MB-Tree", because dark areas will encode bad.

Or you can crank up --qcomp or --aq-strength, or use a lower quantizer. In the end, they'll all give you higher bitrates.

[Selur]

Assuming they land on the same size, which one has superior quality? Should be same?

Yes, the quality should be the same, since they both use the same bit rate distribution algorithms.

about the settings:
we have a bunch of settings which are ment to boost detail preservation and move bit rate to details/edges:

• mb-tree
• trellis
• p4x4

we have some options which influence the bit rate distributionin general

• --qcomp influence the general bit rate distribution (cbr versus cq) and a higher qcomp value will lower the effekt of mb-tree
• using 2pass instead of using crf will also limit the redistribution of bits a bit, but for the same average bit rate the
• --aq-strength directly influences the bit rate distribution between details/edges and flat areas
• --nr will do some dct smoothing and therefore remove some details, which will lower the effect of the bit rate redistribution

-> it's always a fight between details preservation and bit rate for flat areas.

Cu Selur

[Hoser Rob]

And you can use some of those lovely (if complex) encoding options in cfr mode and still encode in comparable time to 2 pass abr mode without them.