no-psy and low bit rate encoding

nibus · 31st July 2011, 00:23

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 · 31st July 2011, 01:23

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 · 31st July 2011, 02:32

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 · 31st July 2011, 15:25

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

upyzl · 31st July 2011, 15:28

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

It uses psy_rd=0.2:0.0

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

31st July 2011, 00:23	#1 \| Link
nibus Telewhining Join Date: Mar 2010 Posts: 272	no-psy and low bit rate encoding 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.

31st July 2011, 01:23	#2 \| Link
Dark Shikari x264 developer Join Date: Sep 2005 Posts: 8,666	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. __________________ Follow x264 development progress \| akupenguin quotes \| x264 git status ffmpeg and x264-related consulting/coding contracts \| Doom10

31st July 2011, 15:25	#4 \| Link
upyzl zj262144 Join Date: Sep 2010 Posts: 105	For ultra low bitrate encoding, I prefer use --psy-rd 0~0.2:0 __________________ MPC-HC 1.7.8 / LAV Filters 0.64+ (tMod) / XySubFilter 3.1.0.705 / madVR 0.87.14 Direct264 Mod (src & win32 builds): code.google.com/p/direct264umod (maybe outdated)

31st July 2011, 15:28	#5 \| Link
upyzl zj262144 Join Date: Sep 2010 Posts: 105	DS had a test for ultra low bitrate video (Jul, 2009 - Just 2 years ago) see http://x264.nl/developers/Dark_Shika...rateanime.html It uses psy_rd=0.2:0.0 What's more, you should know x264 is always updated during these days __________________ MPC-HC 1.7.8 / LAV Filters 0.64+ (tMod) / XySubFilter 3.1.0.705 / madVR 0.87.14 Direct264 Mod (src & win32 builds): code.google.com/p/direct264umod (maybe outdated)

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31st July 2011, 02:32	#3 \| Link
nibus Telewhining Join Date: Mar 2010 Posts: 272	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?