[mythtv] VAAPI rewrite

[Peter Bennett]

On 09/03/2018 03:08 PM, David Engel wrote:
> Nice work, Peter.  I've noticed a couple of things others haven't
> reported yet.
>
> First, all of the VA deinterlacers are enabled in the OSD.  I thought
> when the post processing was added VAAPI that not all deinterlacers
> were supported on all hardware.  Maybe things have changed in recent
> years and I could be wrong.
I did not see a method for finding out which deinterlacers are 
supported, so I added them all. I suppose if you select one that is not 
supported you will get some sort of failure. The default one, which I 
labeled "Advanced" is documented as finding the best supported, so 
hopefully that will always choose a supported one.
> Second, I'm seeing strange issues with skip and ff/rew like when the
> the mediacodec, 2x deinterlacing was first being added.  I think this
> might be realted to the first issue -- for example, a 2x deinterlacer
> is requested, but isn't actually being used and the frame timing is
> getting messed up.  I need to do some more testing to figure out
> what's going on.
I also noticed it, but then I switched to a software decode OpenGL 
profile with a 2x interlacer and saw the same thing, so I decided that 
this may be  an existing problem with the drop prediction logic. If you 
use -v playback you can see it gets ahead then behind then ahead in a 
repeating cycle, so something is wrong with that logic. If it is an 
existing problem I would rather fix it in a separate commit later.
> On the strange observation front, mpeg2 can't time stretch beyond
> around 1.4x without getting choppy, but h.264 can time stretch at or
> near 2x.
Could this be because the h264 is not interlaced or has a lower frame rate?

> David