[mythtv-users] what is this video artifact?

[James Miller]

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.