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Old 12th April 2019, 09:10   #22  |  Link
gdgsdg123
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Join Date: Mar 2019
Posts: 8
Quote:
Originally Posted by benwaggoner View Post
HEVC in particular has intraframe prediction and other advanced tools that should squeeze even more bits out.

They aren’t all on even in —preset placebo, though! Using —cu-lossless and —tskip can help improve efficiency and quality of near-lossless encoding. Cu-lossless allows any given CTU to use lossless mode if it is more efficient; real lossless is just using that for the whole frame.
The docs give somewhat different opinion.





About --tskip:
Quote:
Lossless — x265 documentation

Transform Skip
A somewhat related feature, --tskip tells the encoder to evaluate transform-skip (bypass DCT but with quantization still enabled) when coding small 4x4 transform blocks. This feature is intended to improve the coding efficiency of screen content (aka: text on a screen) and is not really intended for lossless coding. This feature should only be enabled if the content has a lot of very sharp edges in it, and is mostly unrelated to lossless coding.

About --cu-lossless:
Quote:
Command Line Options — x265 documentation

--cu-lossless, --no-cu-lossless
For each CU, evaluate lossless (transform and quant bypass) encode of the best non-lossless mode option as a potential rate distortion optimization. If the global option --lossless has been specified, all CUs will be encoded as lossless unconditionally regardless of whether this option was enabled. Default disabled.

Only effective at RD levels 3 and above, which perform RDO mode decisions.


And 1 thing I must emphasize... near-lossless = lossy.
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