[mythtv] OpenGL, Android and Fire Stick

[Peter Bennett]

With the fire stick I find that video decoding is fast enough for 
regular 1x playback of MPEG2, H264 and H265 up to 1080. However OpenGL 
presents a variety of problems.

There are three sets of shaders for video playback:
yv12: On the fire stick playback is restricted to 15-20 fps, giving a 
rather unpleasant viewing experience. Also there is a fat green line 
along the bottom (as we observed also with shield) and a green line at 
the right.
uyvu: On the fire stick playback speed is much better, but the right 
hand side of the picture has low resolution. Starting from the center of 
the picture, moving to the right the resolution gradually reduces, 
resulting in jagged edges and loss of detail towards the right of the 
picture.
rgb:   On the fire stick playback speed is good, as it is for uyvu. 
There is no picture resolution problem on the right or anywhere, there 
is no green line at the bottom, but the colors are wrong. I thing the 
red color is missing entirely.

The fire stick is capable of reasonable playback speed and of good 
quality picture, but the OpenGL needs some changes. I think part of it 
may be the differences between OpenGL and OpenGL ES.

I have little understanding of OpenGL, so I am going through the OpenGL 
ES book and examples, to try to get an understanding of what goes on in 
those shaders, so that I can create shaders that works with good 
performance and quality in this situation. At the same time I hope to 
eliminate the green line problem so that yv12 can be used when needed.

Peter