no-psy and low bit rate encoding

[nibus]

I've recently found that the no-psy option can dramatically lower the bitrate when doing CRF encoding. However I've also noticed the picture is a little less defined in some scenes, obviously because of the lack of psy optimizations.

My question is this: For lower bitrate encoding (say 640x360 / CRF ~22-24 / ~250-300 kbps) in your opinion would you achieve better results by leaving psy on and raising the CRF value, or turning psy off and lowering the CRF value? I've read in some threads that psy at a low bitrate can produce unwanted artifacts and ringing. Of course the alternative with psy off is a slightly blurred picture in some places.

[Dark Shikari]

Never turn off --psy, ever.

If you disagree with certain psy optimizations (e.g. psy-RD), turn them off individually. --no-psy doesn't merely force off psy-RD; it also forces off things you should never, ever turn off, as they undoubtedly have a negative impact on visual quality.

[nibus]

thanks for the info DS. I actualy read in an older thread here to disable psy altogether for low bitrates. what specific psy tweaks would you recommend for low bitrates? just disabling psy-RD?

[upyzl]

For ultra low bitrate encoding, I prefer use --psy-rd 0~0.2:0

[upyzl]

DS had a test for ultra low bitrate video (Jul, 2009 - Just 2 years ago)
see http://x264.nl/developers/Dark_Shikari/Flash/lowbitrateanime.html

It uses psy_rd=0.2:0.0

What's more, you should know x264 is always updated during these days