[x265] Ghosting/artifacts even with low CRF

[Rômulo Silva]

Some more info on the issue.


I updated my x265 encoder to 1.9+167 and tested the same sample with the
same parameters (CRF 21, 10-Bit, preset slower) with --no-recursion-skip as
the only additional parameter.


x265 hardsub sample [--no-recursion-skip]:
http://www.mediafire.com/download/lx98hc6n5b40db2/hardsub+test+norecursionskip.mkv


The result is much better compared to not using the --no-recursion-skip
parameter, but there's still some ghosting on both books in the scene
around the letters. File size is around 10% bigger, and encoding time was
more or less 50% slower just like pointed out here:
http://forum.doom9.org/showthread.php?p=1767551#post1767551


Thanks again,

R.S.

On Mon, May 9, 2016 at 5:59 PM, Rômulo Silva <rsilva2k5 at gmail.com> wrote:

> This is related to issue #214:
> https://bitbucket.org/multicoreware/x265/issues/214/ghosting-artefacts-even-with-low-crf-when
>
>
> Turns out that it's easy to reproduce the problem with hardsubs, and I've
> included both x264 and x265 samples below to illustrate this.
>
>
> Lossless x264 sample:
> http://www.mediafire.com/download/ftwysmcemw7211a/x264+crf0.mkv
> Sample subtitle:
> http://www.mediafire.com/download/jttvyk2k0va9c3g/lorem+ipsum.ass
> x264 hardsub sample:
> http://www.mediafire.com/download/nzp7pzz5y8h7yjy/hardsub_test_x264.mkv
> x265 hardsub sample:
> http://www.mediafire.com/download/mz51v2a8d99pa5t/hardsub+test.mkv
>
>
> Both hardsub files were encoded with CRF 21, 10-Bit and slower preset.
> X265 encoder version was 1.9+150-00ea3784bd36.
>
> You can clearly see the artifacts between the two lines on top of the left
> book. Some ornaments get distorted around the letters, and straight edges
> don't move according to the scene.
>
> A few suggested workarounds, like --no-cutree, make the ghosting less
> apparent, but it still doesn't solve the issue completely. I've included
> below a sample of the same x265 encode used above (CRF 21, 10-Bit, slower)
> with --no-cutree as the only additional parameter.
>
>
> x265 hardsub sample [--no-cutree]:
> http://www.mediafire.com/download/abvwr1jbp47uw29/hardsub_test_nocutree.mkv
>
>
> The resulting file has over twice the size, and even though the artifacts
> on ornaments are mostly gone, some straight edges in between the lines are
> still not moving according to the scene.
>
> Has any progress been made on this issue? I'm willing to help by providing
> more samples and test cases, if needed.
>
>
> Thanks for your attention,
>
> R.S.
>
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