[mythtv] Kernel 2X HW-GL Deinterlacing

David Engel david at istwok.net
Mon Nov 26 02:03:22 UTC 2018

On Sat, Nov 24, 2018 at 05:25:30PM -0500, Peter Bennett wrote:
> On 11/24/18 12:42 PM, David Engel wrote:
> > The effect I see on my Shields when reversed is not selected is very
> > much like a non-deinterlaced image -- the alternating scan lines are
> > offset by a few pixels.  It's most apparent on scrolling news tickers.
> > When reversed is selected, the scan lines all line up nicely.  Have
> > you tried it on your Shield?
> > 
> > What's troubling is the inconsistency.  Mark's comment about the
> > coordinates being different between OpenGL and OpenGLES could explain
> > why the Shield needs reversed selected to look good.  If that was
> > true, though, I'd expect selecting reversed to look bad on Linux but
> > it doesn't.
> > 
> I tried it on my shield, with standard decode and opengl  display - using
> HW-GL deinterlacers -
> Kernel 2x - the ticker looks double, two flickering copies of it scrolling -
> most unpleasant.
> Kernel 2x with interlace reversed selected - perfect.
> Kernel 1x - the ticker shakes while scrolling.
> Kernel 1x with interlace reversed selected - smoother, almost perfect.
> Linear Blend 2x - perfect
> Linear Blend 2x with interlaced reversed selected - the ticker looks double,
> two flickering copies of it scrolling - most unpleasant.

Hmm, I would have sworn I'd tested this.  I just redid and, yes, I now
see the obvious distortion when turning on reversed with linead blend.
What do you see with Linux/full OpenGL?

> Linear Blend 1x - ticker shakes while scrolling
> Linear Blend 1x with interlaced reversed - same as with interlaced normal -
> ticker shakes while scrolling
> In 2x deinterlace, Linear blend and kernel seem equal, except that kernel
> gets it wrong by needing the interlace reversed.
> in 1x deinterlace, kernel is better but gets it wrong by needing interlace
> reversed.
> I am afraid I cannot offer any hope as far as understanding the OpenGL is
> concerned, it seems to be a very complicated subject.

The above leads me to believe there is simply a bug in the kernel,
OpenGL code.  I will endeavor to try to figure it out.  Not really
knowing OpenGL nor the kernel algortith, I don't know know how long it
will take.

David Engel
david at istwok.net

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