It looks like DOTA2 has the most extreme examples of single-pixel transitions between brightly saturated to no chroma, so I'll do some test runs like that.
On an initial test with Witcher 3, CRF 18 still left a lot of visible blocking and banding. The default aq settings aren't well tuned/effective adapting for that sort of material. DOTA2 is quite different, so I'm going to stick with CRF 18 to start.
Bitrates were pretty much identical between 420 and 444, probably because of:
Code:
x265 [warning]: halving the quality when psy-rd is enabled for 444 input. Setting cbQpOffset = 6 and crQpOffset = 6
Which should make apples-to-apples comparisons easier, as the same amount of bits should be allocated to both luma and chroma in either mode. Although any potential gain from 444 might require lower Qps for chroma to retain those edges.
Here's the DOTA2 command line I'm kicking off. These seem reasonable?
Code:
ffmpeg.exe -i DOTA2.mov -pix_fmt yuv420p -f yuv4mpegpipe - | x265.exe - --y4m --preset slower --pools "+,-" --keyint 240 --crf 18 --vbv-maxrate 5000 --vbv-bufsize 15000 -o DOTA2_CRF-18.hevc
ffmpeg.exe -i DOTA2.mov -pix_fmt yuv444p -f yuv4mpegpipe - | x265.exe - --y4m --profile main444-8 --preset slower --keyint 240 --crf 18 --vbv-maxrate 5000 --vbv-bufsize 15000 -o DOTA2_CRF-18-444.hevc