[mythtv-users] Hard frontend crash with vaapi on Ubuntu 20.04 and Mythtv 31

OpenMedia Support support at openmedia.co.nz
Tue Jun 1 15:51:31 UTC 2021


> On Wed, 2 Jun 2021 02:16:28 +1200, you wrote:
>
>>>
>>> On 6/1/21 7:05 AM, OpenMedia Support wrote:
>>>>> On 6/1/21 3:38 AM, OpenMedia Support wrote:
>>>>>> I'm running an Intel N3150 based NUC as a dedicated frontend for
>>>>>> MythTV
>>>>>> and it keep getting hard crashes during video playback with VAAPI.
>>>>>> Id
>>>>>> appreciate some guidance on how to best debug the problem.
>>>>>>
>>>>>> Hardware - Gigabyte Brix Intel N3150 / 4GB Ram / 120GB SSD
>>>>>>
>>>>>> OS - Ubuntu 20.04 LTS - regularly patched
>>>>>>
>>>>>> MythTV Backend - on different hardware with DVB-T and DVB-S cards
>>>>>>
>>>>>> MythTV Frontend - Lastest version from the PPA -
>>>>>> http://ppa.launchpad.net/mythbuntu/31/ubuntu
>>>>>>
>>>>>> Video playback currently uses a custom VAAPI profile, but the out of
>>>>>> the
>>>>>> box VAAPI profile also has issues. It appears to occur when playing
>>>>>> H.264
>>>>>> based content. Our DVB-T FTA service is H.264 for both HD and SD
>>>>>> material.
>>>>>> It can occur when we're simply watching a show, and the video /
>>>>>> audio
>>>>>> freezes and I need to hard-reset the Brix hardware.
>>>>>>
>>>>>> I've configured for
>>>>>>    - max_cpus = 3
>>>>>>    - deinterlacer - low:shader:driver
>>>>>>    - decoder - vaapi
>>>>>>    - videorender - opengl-hw
>>>>>>    - skiploop - 0
>>>>>>
>>>>>> I'll try and reproduce with "-v playback" enabled but at present
>>>>>> there
>>>>>> is
>>>>>> nothing obvious in the frontend or system logs when the crash
>>>>>> occurs.
>>>>>>
>>>>>> I'd really appreciate it if anyone else seen similar issues and
>>>>>> could
>>>>>> provide guidance.
>>>>>
>>>>> I have a NUC i7-1165G7 and it has Iris graphics.  I can't get
>>>>> VAAPI
>>>>> to
>>>>> work at all. I have to use OpenGL low quality deinterlacing. When I
>>>>> use
>>>>> VAAPI it crashes with code 139. I can't run higher than low
>>>>> deinterlacing because the pictures tears about 10% from the top of
>>>>> the
>>>>> screen.
>>>>>
>>>>> Luckily, I didn't buy the $800 NUC as a mythtv frontend only. Iris
>>>>> GFX
>>>>> and Mythtv aren't a good solution for sure.
>>>>>
>>>> The N3150 Brix was relatively cheap and generally makes quite a nice
>>>> front
>>>> end, and now it has an SSD is effectively silent.
>>>>
>>>> Just had a fresh hard crash with "-v playback" and all I can see is
>>>> the
>>>> following as I had an SSH session tailing the frontend logs.
>>>>
>>>> Jun  1 21:49:37 mythfe1 mythfrontend.real: mythfrontend[1900]: I
>>>
>>> Are you able to get into ssh to kill the frontend when it locks up? I
>>> would say the thing to do is enable core files by setting the limit and
>>> disabling Ubuntu crash logging, then when it happens run kill SIGQUIT
>>> to
>>> create a core dump which can be analyzed to see where the hang
>>> occurred.
>>
>>Afraid not. This is a hard crash and I loose my SSH sessions. I've been
>>running a couple of sessions to tail the mythfrontend and system logs and
>>they become responsive until I reboot the hardware.
>
> Have you tried using the magic keys to see if you can get the
> filesystem buffers to flush before rebooting?  Sometimes you can get
> some log information that way.
>
> In /etc/sysctl.conf, put:
>
> kernel.sysrq=1
>
> to allow all the magic keys.  Run "sysctl --system" to reload the
> sysctl.conf settings, or reboot.  Then when the next lockup happens,
> hold down the Alt and SysReq keys, then with both down type this
> sequence:
>
> REISUB
>
> If your keyboard does not have a SysReq key marked, it is also usually
> the PrntScrn key.
>
> See here for what each keystroke does:
>
> https://en.wikipedia.org/wiki/Magic_SysRq_key
>
> The S and U are the critical ones - they sync and unmount the
> filesystems.
>
> Your problem has the same characteristics as what I had when I first
> installed my Nvidia GT1030 card.  In my case, it was an Nvidia driver
> bug and it became much less common with a driver update in the same
> series, and went away completely with a major driver update.

Thanks for the tip. I've enabled the setting.

I've also enabled the HWE kernel and switched from 5.4.0.73.76 to
5.8.0.53.60 to see if that will help




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