How to preserve dark lines when re-encoding anime to x265?

[Felow]

Obsolete

[Alkl]

You already have pretty much "the" settings for anime encoding.

Also avoid the "animation" preset for anime, if you thought about it.

Here an excerpt from kokomins:

TL;DR Summary for x265 Encode Settings

Set preset=slow. Then choose 1 following to override the default parameters. These are my recommended settings, feel free to tune them.

• 1 Setting to rule them all: crf=19-20,

  limit-sao:bframes=8:psy-rd=1:aq-mode=3

• Flat, slow anime (slice of life, everything is well lit): crf=19-20,

  bframes=8:psy-rd=1:aq-mode=3:aq-strength=0.8:deblock=1,1

• Some dark scene, some battle scene (shonen, historical, etc.): crf=18-19 (motion + fancy FX),

  limit-sao:bframes=8:psy-rd=1.5:psy-rdoq=2:aq-mode=3

• Movie-tier dark scene, complex grain/detail: Movie-tier dark scene, complex grain/detail: crf=16-18,

  no-sao:bframes=8:psy-rd=1.5:psy-rdoq=4:aq-mode=3

• I have infinite storage, a supercomputer, and I want details: preset=veryslow, crf=14,

  no-sao:no-strong-intra-smoothing:bframes=8:psy-rd=2:psy-rdoq=5:aq-mode=3:deblock=-1,-1:ref=6

Here an excerpt from a Reddit poster:

• Use the 10-bit encoder. Not the 8-bit nor the 12-bit.
• Optimally, use the slow preset. Veryslow preset is a luxury reserved for very powerful systems and high crf (22+) encodes.
• aq-mode=3! This sets dark scene aq bias, which is really helpful for anime, as this is where most of the artifacts and banding will be.
• Don't use tune animation. The appended options are: psy-rd=0.4:aq-strength=0.4:deblock=1,1:bframes=(preset+2). These are optimized for cartoon-style animation, anything more complex than slice of life is going to suffer, especially with newer BD releases utilizing dynamic grain to prevent banding. For "Anime" anime, I recommend psy-rd1 to 2 (more complex/action packed/detailed anime = higher value needed, also increases bitrate), aq-strength 0.6 to 1 (more complex/detailed = need higher value, don't go beyond 1 as you may introduce ringing artifacts. You will mostly use 0.8-1. Also raises bitrate.), deblock -1:-1 to 1:1 (depends on source, leave on 0:0 if you don't know what to use) and bframes 4 to 8 (I highly recommend 6, 8 if possible. Encode penalty is only ~5% going from 4 to 8). Additionally, if your source has grain, psy-rdoq should be raised from the default 1 to 3-5 depending on source (note: only combine higher rdoq with crf<18 and no-sao, or you'll end up with grain "blocks" instead of grain "grain").
• Use limit-sao for crf 17-19. Use no-sao for crf<18 if there are fine grain present. Else leave on default.
• Use no-strong-intra-smoothing only for crf<16. This helps preserve fine details. High crf will result in blocking due to lack of smoothing on 32x32 blocks.

[Felow]

You already have pretty much "the" settings for anime encoding.

Also avoid the "animation" preset for anime, if you thought about it.

Here an excerpt from kokomins:

TL;DR Summary for x265 Encode Settings

Set preset=slow. Then choose 1 following to override the default parameters. These are my recommended settings, feel free to tune them.

• 1 Setting to rule them all: crf=19-20,

  limit-sao:bframes=8:psy-rd=1:aq-mode=3

• Flat, slow anime (slice of life, everything is well lit): crf=19-20,

  bframes=8:psy-rd=1:aq-mode=3:aq-strength=0.8:deblock=1,1

• Some dark scene, some battle scene (shonen, historical, etc.): crf=18-19 (motion + fancy FX),

  limit-sao:bframes=8:psy-rd=1.5:psy-rdoq=2:aq-mode=3

• Movie-tier dark scene, complex grain/detail: Movie-tier dark scene, complex grain/detail: crf=16-18,

  no-sao:bframes=8:psy-rd=1.5:psy-rdoq=4:aq-mode=3

• I have infinite storage, a supercomputer, and I want details: preset=veryslow, crf=14,

  no-sao:no-strong-intra-smoothing:bframes=8:psy-rd=2:psy-rdoq=5:aq-mode=3:deblock=-1,-1:ref=6

Here an excerpt from a Reddit poster:

• Use the 10-bit encoder. Not the 8-bit nor the 12-bit.
• Optimally, use the slow preset. Veryslow preset is a luxury reserved for very powerful systems and high crf (22+) encodes.
• aq-mode=3! This sets dark scene aq bias, which is really helpful for anime, as this is where most of the artifacts and banding will be.
• Don't use tune animation. The appended options are: psy-rd=0.4:aq-strength=0.4:deblock=1,1:bframes=(preset+2). These are optimized for cartoon-style animation, anything more complex than slice of life is going to suffer, especially with newer BD releases utilizing dynamic grain to prevent banding. For "Anime" anime, I recommend psy-rd1 to 2 (more complex/action packed/detailed anime = higher value needed, also increases bitrate), aq-strength 0.6 to 1 (more complex/detailed = need higher value, don't go beyond 1 as you may introduce ringing artifacts. You will mostly use 0.8-1. Also raises bitrate.), deblock -1:-1 to 1:1 (depends on source, leave on 0:0 if you don't know what to use) and bframes 4 to 8 (I highly recommend 6, 8 if possible. Encode penalty is only ~5% going from 4 to 8). Additionally, if your source has grain, psy-rdoq should be raised from the default 1 to 3-5 depending on source (note: only combine higher rdoq with crf<18 and no-sao, or you'll end up with grain "blocks" instead of grain "grain").
• Use limit-sao for crf 17-19. Use no-sao for crf<18 if there are fine grain present. Else leave on default.
• Use no-strong-intra-smoothing only for crf<16. This helps preserve fine details. High crf will result in blocking due to lack of smoothing on 32x32 blocks.

Well, it looks like there's no way to preserve dark lines without lowering the CRF even more.

Thank you for answering.