[x265] Recommended settings for low-resolution encoding with --hevc-aq

[nalla shanaha]

Hello,
I hope this list is the right place to ask a question as an end-user.

I use libx265 via the ffmpeg plugin. I find that enabling --hevc-aq
(with -x265-params "hevc-aq=1"), reduces bit-rate by a very large
amount (keeping crf constant). The output quality is excellent for
480p and higher resolutions. However, for 360p/240p etc, enabling
--hevc-aq tends to produce some pixellation. This is particularly
prominent around the edges of objects in the video.

I understand that there is no free lunch, and the reduction in bitrate
(at same crf) between --no-hevc-aq and --hevc-aq does mean that there
will be some quality loss. But are there some parameters that can be
tuned to minimize this blocking/pixellation ?

For example, in my tests, using 10-bit output (-pix_fmt yuv420p10le)
and changing to a slower preset ('slow' or 'slower' instead of medium)
seems to help. Are there any other parameters that could be modified?

thanks.