[x265] Ghosting/artifacts even with low CRF

[Rômulo Silva]

Hello.


There you go:
http://www.mediafire.com/download/crmj9d7ylsg32dm/x264_crf0_hardsub.mkv

Encoded with x264, revision 2692, 10bit, preset veryslow, CRF 0.


Cheers,

R.S.

On Fri, Jul 15, 2016 at 8:56 AM, Deepthi Nandakumar <
deepthi at multicorewareinc.com> wrote:

> 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.
>>>
>>
>>
>> _______________________________________________
>> x265-devel mailing list
>> x265-devel at videolan.org
>> https://mailman.videolan.org/listinfo/x265-devel
>>
>>
>
>
> --
> Deepthi Nandakumar
> Engineering Manager, x265
> Multicoreware, Inc
>
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
>
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