[x265] Ghosting/artifacts even with low CRF

[Deepthi Nandakumar]

Hi,

Sorry I couldnt get to this before v2.0. Can you share a file with the
subtitles burned into the x264-crf0 lossless video?

Thanks,
Deepthi

On Sun, May 15, 2016 at 3:49 AM, Rômulo Silva <rsilva2k5 at gmail.com> wrote:

> 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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>


-- 
Deepthi Nandakumar
Engineering Manager, x265
Multicoreware, Inc
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