[x265] x265 crashes/gets stuck when giving more than '--slices 16'

Tue Mar 14 17:13:41 CET 2017

Good morning Michael,

I made a restrict on count of slices because we have limited number of output NAL buffers.
Every slices need a independent NAL, but the SPS/PPS/VPS will also allocate at least one of NAL, so I made slices limit to (MAX_NAL_UNITS - 1)

Best regards,
Min

At 2017-03-14 15:23:03,"Michael Lackner" <michael.lackner at unileoben.ac.at> wrote:
>Good morning!
>
>I applied the patch and rebuilt the code (2.3+9-820f4327ddac in this case).
>
>Invoking x265 on a 8292x3428 video with '--slices 20' now gives the following warning:
>
>x265 [warning]: maxSlices can not be more than min(rows, MAX_NAL_UNITS-1), force set to 15
>
>And it shows:
>
>x265 [info]: Slices                              : 15
>
>Just a laymans' question: I can see in source/encoder/nal.h, that MAX_NAL_UNITS is 16.
>Should maxSlices really be MAX_NAL_UNITS-1 and not MAX_NAL_UNITS in this case? I'm just
>asking because encoding with 16 slices seemed to work just fine before the patch.
>
>Or are there issues with that?
>
>Thanks!
>
>Best,
>Michael
>
>-- 
>Michael Lackner
>Lehrstuhl für Informationstechnologie (CiT)
>Montanuniversität Leoben
>Tel.: +43 (0)3842/402-1505 | Mail: michael.lackner at unileoben.ac.at
>Fax.: +43 (0)3842/402-1502 | Web: http://institute.unileoben.ac.at/infotech
>
>On 03/14/2017 05:15 AM, Pradeep Ramachandran wrote:
>> The limit check was checking against the wrong variable - it should've
>> checked against slicesLimit and not against numRows.
>> Can you please check if https://patches.videolan.org/patch/15905/ solves
>> your issue?
>> 
>> Pradeep Ramachandran, PhD
>> Solution Architect at www.multicorewareinc.com/
>> Adjunct Faculty at www.cse.iitm.ac.in/
>> pradeeprama.info/
>> Ph:   +91 99627 82018
>> 
>> On Mon, Mar 6, 2017 at 4:30 PM, Michael Lackner <
>> michael.lackner at unileoben.ac.at> wrote:
>> 
>>> Greetings,
>>>
>>> During my experimentation with creating a x265-based benchmark, I found
>>> out that x265
>>> segfaults and/or freezes when giving it more than 16 frame slices to
>>> encode (e.g. --slices
>>> 17 or --slices 20 or --slices 32 or similar).
>>>
>>> It seems easy to reproduce as well. In my case, I'm feeding raw 16-bit YUV
>>> 4:4:4 content
>>> to it (16-bit per channel, 48-bit per pixel, no chroma subsampling). The
>>> resolution is
>>> 8192×3428, an upscale of the free movie "Tears of Steel".
>>>
>>> It works perfectly fine with <=16 slices on all my systems though, here's
>>> the ones I've
>>> tested it on:
>>>
>>> Environments / software versions:
>>>
>>>   * x265 2.2+22-20217c8af8ac
>>>
>>>      CentOS 6.8 Linux x86_64, x265 built by GCC 6.2.0 + yasm 1.3.0
>>>       => Segmentation fault
>>>
>>>   * x265 2.3+9-820f4327ddac
>>>
>>>     o CentOS 6.8 Linux x86_64, x265 built by GCC 6.2.0 + yasm 1.3.0
>>>       => Segmentation fault
>>>
>>>     o FreeBSD 10.3 UNIX x86_64, x265 built by clang 3.8.1 + yasm 1.3.0
>>>       => Process locks up in STOP state and becomes unkillable, even
>>>          to SIGKILL
>>>
>>>     o Windows XP Professional x64 Edition (NT5.2), x265 built by
>>>       MSVC2010 SP1, cl.exe 16.00.40219.01 + yasm 1.3.0
>>>       => Terminates with %ERRORLEVEL% still set to 0, so this crash is
>>>       completely uncaught
>>>
>>> As said, it works fine on all platforms with --slices [1..16].
>>>
>>> Here's some sample output of the crash from Linux, it's supposed to be a
>>> 2-pass encode:
>>>
>>> 29163 Segmentation fault      (core dumped) nice -n19 x265 ./raw8k.yuv
>>> --frames 500
>>> --input-depth 16 --dither --input-res 8192x3428 --input-csp i444 -D 10
>>> --fps 24 --slices
>>> 20 -p veryslow --pmode --pme --open-gop --ref 6 --bframes 16 --b-pyramid
>>> --weightb
>>> --max-merge 5 --b-intra --bitrate 50000 --rect --amp --aq-mode 2 --no-sao
>>> --qcomp 0.75
>>> --no-strong-intra-smoothing --psy-rd 1.6 --psy-rdoq 5.0 --rdoq-level 1
>>> --tu-inter-depth 4
>>> --tu-intra-depth 4 --ctu 32 --max-tu-size 32 --pass 1 --slow-firstpass
>>> --stats v.stats
>>> --sar 1 --range full -o pass1.h265
>>>
>>> I don't have any debug builds of x265 right now and I don't really know
>>> how to even do any
>>> debugging, but if you can tell me if you need anything, I can always try
>>> to build a debug
>>> version to generate more helpful output / dump files.
>>>
>>> Or maybe 16 frame slices are supposed to be the maximum, but it's just not
>>> handled
>>> correctly yet?!
>>>
>>> Is there any information available on that behavior?
>>>
>>> --
>>> Michael Lackner
>>> Lehrstuhl für Informationstechnologie (CiT)
>>> Montanuniversität Leoben
>>> Tel.: +43 (0)3842/402-1505 | Mail: michael.lackner at unileoben.ac.at
>>> Fax.: +43 (0)3842/402-1502 | Web: http://institute.unileoben.ac.
>>> at/infotech
>>> _______________________________________________
>>> x265-devel mailing list
>>> x265-devel at videolan.org
>>> https://mailman.videolan.org/listinfo/x265-devel
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