[mythtv-users] SD looks worse under vaapi normal playback profile

[Michael T. Dean]

On 02/11/2016 03:13 PM, James Miller wrote:
> I've got the Liva X which has Intel Corporation Atom Processor 
> Z36xxx/Z37xxx Series Graphics & Display--video hardware that, from 
> everything I've gathered, is vaapi-compatible. I'd been unable to 
> compile MythTV with vaapi support until just recently and had been 
> using the normal (non-vaapi) playback profile on this system. I 
> finally managed to get MythTV to compile with vaapi support and have 
> begun trying out the vaapi normal playback profile.
>
> It's hard to tell much difference in HD playback (contrary to most, I 
> consider 720p to be HD), but I'd say there may be a slight improvement 
> using vaapi normal, as opposed to the normal, playback profile I'd 
> been using, when viewing HD content. But when it comes to SD playback, 
> the vaapi normal playback profile looks noticeably worse than it does 
> under the normal profile. I'm not real conversant in video effects 
> nomenclature but I believe what I am seeing under the vaapi normal 
> playback profile when viewing SD content may qualify as "combing." To 
> add a verbal description, one of the chief things I notice when 
> playing back SD content under the vaapi normal profile is that when 
> some there is in the picture some line that runs on a diagonal with 
> respect to the screen borders, that line is noticeably stepped and not 
> very smooth. Under the normal playback profile, on the other hand, I 
> can barely note this sort of stepping on such diagonal lines.
>
> So I just wanted to ask here whether there might be any further 
> adjustment I may need to make in order to get better results under the 
> vaapi normal playback profile when viewing SD content? I've done a 
> little research on this and noted a wiki article on the vaapi normal 
> playback profile. My painter had been set to "auto," as the wiki 
> article recommended. I also tried opengl as the painter, but results 
> were the same--the sort of combing I described was just as apparent, 
> whether the painter was set to "auto" or to "opengl."

Painter only affects the GUI (menu portion) of MythTV, not playback.  
The only reason the wiki says to use Auto (or OpenGL) is, TTBOMK, 
because VA-API itself isn't available (or doesn't work) if the GUI is 
using the Qt painter.

>
> Maybe the vaapi normal playback profile just does not handle well SD 
> playback? Input will be appreciated.

Does VA-API/our implemented version of VA-API/MythTV's use of VA-API 
support deinterlacing, yet?  I'm pretty sure the answer to at least one 
of these questions is no, meaning the problem is you're not 
deinterlacing the video when you use VA-API.  So, 720p video looks 
good.  480i looks bad.  1080i probably looks bad, but because of the 
increased resolution, will likely require closer inspection to see the 
interlacing artifacts.

I'm sure someone else can give you the current state of VA-API/MythTV's 
implemented version of VA-API/MythTV's use of VA-API vs deinterlacing.

Mike