x264 crf 18 = x265 crf ? & qsvenc icq ?

[cscxk]

with x264, i like used crf 18 to rip blu-ray, now use x265, i heard x265 crf 27-28 = x264 crf 24, like that x264 crf 18=x265 crf 21? How to calculate this?

and so, i need set how many q for qsvenc hevc icq to like x264 crf 18's Quality

[dipje]

no real way to calculate. Experiment what your own preference is.

And the same is for 'q': There is no real answer. The whole thing 'crf' is crf, is because it isn't just 'a q'. It tries to determine what we experience as quality and tries to be the same.
A constant-q factor is just that, a constant q. It might be that there are worse parts or better parts, no real equalevant.

What q-factor you want is the same answer as the first one: Try for yourself. Make a short test encode, with something like a clip with little motion that goes into high motion (or a little clip of a dialog or something, then paste a little clip of action scene after it. Little 30 to 60 second total testclip with high motion and low motion, try for yourself what values you end up with).

All I can say is that in my experience, modern x265 crf values and x264 values seem to 'come together' more around the 'crf 20' mark. In other words, I did some crf20 x264 encodes and ended up with x265 around crf21 or crf22 but not higher. That was with animated content though, and who knows what you're looking for when you judge quality, so once again: decide for yourself :).

[filler56789]

Not an actual /direct answer to the OP's question, but......

First,

http://forum.doom9.org/showthread.php?t=137465

and then,

http://www.cnblogs.com/lakeone/p/5436481.html

Assuming the 2nd page means what I presume /hope it means :o

— well, it's just a matter of doing the math.

[benwaggoner]

Note that CRF~QP only roughly. It's on the same log scale as QP, but with an offset based on frame complexity. I wouldn't expect it to map linearly to any other quality control algorithms.

[Clare]

Based on my very unscientific tests on 30 short clip, x265 crf = x264 crf - 2