[mythtv-users] what is this video artifact?

[Erik Hovland]

On Tue, May 12, 2015 at 6:56 PM, James Miller <gajs-f0el at dea.spamcon.org> wrote:
> On Sat, 18 Apr 2015, Jim Stichnoth wrote:
>
>> On Sat, Apr 18, 2015 at 11:36 AM, James Miller <gajs-f0el at dea.spamcon.org>
>> wrote:
>>
>>> I note a video artifact under certain conditions when watching any HD
>>> recording. The artifact is either absent or too difficult to notice when
>>> viewing SD recordings. Further, the artifact is only noticeable in HD
>>> recordings in certain instances: I note it when, for example, the camera
>>> is
>>> panning up or down or side-to-side, or when the frame includes a lot of
>>> movement toward the top of the screen. The artifact can be described as a
>>> series of horizontal lines that seem to get out of sequence about one
>>> quarter of the distance from the top of the screen. Once the panning or
>>> movement stops, the horizontal lines are gone and the display returns to
>>> normal--the artifact only showing up again once this panning or movement
>>> begins again. All in all the artifact shows up only very briefly and
>>> sporadically.
>>>
>>> So, what is the artifact? I'm not much of a video connoisseur, so it just
>>> constitutes a minor annoyance for me: I can live with it. But if there is
>>> some simple way of fixing it, I might give that a try.
>>>
>>> This sounds like it might be tearing.
>>
>> http://en.wikipedia.org/wiki/Screen_tearing (though their example looks
>> much cleaner than the tearing I've seen)
>>
>> Depending on your setup, there are a number of things you might do to fix
>> it.
>
>
> I've been going on the assumption that, as Jim had suggested, the video
> artifact I was seeing is tearing. Today, while perusing a Gentoo forum
> thread dedicated to hardware very similar to mine and that I've reviewed
> many times already, I noted something about tearing that, for whatever
> reason, had previously not registered. The suggestion was to enable the
> '"TearFree" graphics driver option.' I researched that further and found
> some helpful instructions on the Arch wiki for enabling that (it involves
> introducing a stanza in the file /etc/X11/xorg.conf.d/20-intel.conf). Once
> I'd done that, adding to it another slight modification I'd found on a
> different Gentoo forums thread dedicated to this issue, I killed and
> restarted X. Lo and behold, that seems to have resolved the slight bit of
> tearing I was seeing intermittently when I would watch HD recordings on this
> machine. So the artifact turns out, apparently, not to have been related to
> vaapi after all.

Would it be possible to share some of the links you talk about above?
I have Liva X running mythbuntu and I have noticed some tearing along
the upper quarter part of the TV while displaying HD content. Changing
between vaapi and regular ffmpeg playback seems to have little if any
affect.

Thanks

E


-- 
Erik Hovland
erik at hovland.org
http://hovland.org/