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Old 11th April 2019, 14:10   #21  |  Link
Asilurr
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A couple of tests on video content generated from still images.

#1 Lenna (preview: wikipedia.org/wiki/File:Lenna_(test_image).png; download: lenna.org), 512x512 RBG24 converted to 8-bit 4:4:4.
x264vs || relative filesize 100.0%
x265vs || 104.7%

#2 M87* (preview: wikipedia.org/wiki/File:Black_hole_-_Messier_87.jpg; download: eso.org/public/archives/images/original/eso1907a.tif), 7416x4320 RGB48 converted to 3708x2160 10-bit 4:4:4. Do note that the original TIFF is a gargantuan 183 MB file.
x264vs || 100.0%
x264f || 100.8%
x265vs || 103.2%
x265f || 104.2%
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Old 12th April 2019, 09:10   #22  |  Link
gdgsdg123
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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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Old 14th April 2019, 12:10   #23  |  Link
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Heavily filtered video might sometimes benefit from tskip, but natural video never will. And since x265 doesn't even implement the screen coding range extensions, the actual capabilities of tskip and other screen coding tunings are very nerfed.
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Old 20th April 2019, 07:25   #24  |  Link
pookpooi
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The rumored Sony's new video codec XEVC which is based on HEVC version 2 claims 240Mbps peak bitrate lossless compressing 1920 x 1080, 12 bit depth, 24fps. I did a calculation and get 1:7.12 ratio.

source: https://www.eoshd.com/2018/12/sonys-...aw-at-240mbit/
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Old 22nd April 2019, 23:53   #25  |  Link
benwaggoner
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Quote:
Originally Posted by pookpooi View Post
The rumored Sony's new video codec XEVC which is based on HEVC version 2 claims 240Mbps peak bitrate lossless compressing 1920 x 1080, 12 bit depth, 24fps. I did a calculation and get 1:7.12 ratio.

source: https://www.eoshd.com/2018/12/sonys-...aw-at-240mbit/
Visually lossless at that rate is certainly feasible, but mathematically lossless is impossible unless they're doing some sort of prefiltering.
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Old 16th July 2019, 13:00   #26  |  Link
gdgsdg123
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Quote:
Originally Posted by poisondeathray View Post
FFV1 (in interframe mode)...
Hmm?..
Quote:
FFV1 Video Codec Specification

The FFV1 video codec is a simple and efficient lossless intra-frame only codec.


Quote:
Originally Posted by poisondeathray View Post
If source has identical content, duplicate frames, then lagarith can be better (null frame option)
I doubt it.

As Lagarith is sort of an old outdated codec... And more advanced codecs (like x264, x265) should have implemented similar capabilities in the algorithms.
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