[mythtv] Deinterlacer settings

[Mark Kendall]

On Tue, 19 Feb 2019 at 15:59, David Engel <david at istwok.net> wrote:
> Mark, there is an issue with our current mediacodec/opengl
> implementation.  With interlaced content, one of the first few frames
> after a skip (including skips for ff/rew) gets corrupted and includes
> image data from two different frames.  This problem reportedly doesn't
> occur when using Android's natvice Surface format for rendering.  Are
> you aware of that issue and done anything about it?  I've been meaning
> to try the render branch to see if it still exists.

I've not seen this but will have a look. That sounds like a reference
frame issue with the active deinterlacer. From our perspective, that
would only happen if using the kernel deinterlacer. Thinking about it,
we don't reset the reference frames after a seek (which we do with
VDPAU) - so there is something to look at there. If it is the
mediacodec deinterlacer doing the same, then I'm not sure how we deal
with that. Perhaps we need to flush the decoder properly (though this
should already be happening).

Also, have you
> dont anything else in the mediacodec area yet to avoid extra copying?

I've been looking at this but am still largely in the dark. The FFmpeg
mediacodec code accepts a single 'surface' as an option when it is
configured (which we obviously do not currently use). There is no
documentation on how to use it. Looking at the kodi (or maybe mpv?)
code - there is one implementation that uses this configuration - but
the 'surface' they supply is the window id and the implementation is
called 'embedded' - so i can only assume that this somehow renders
directly to the screen. Not ideal but could still be workable if we
can still render the OSD etc on top. Other implementations do not use
FFmpeg. Based on a comment in the libqtav code, there is clearly the
possibility of integrating mediacodec directly into OpenGL - but that
part of the code is closed source and not available:( and it is
unclear whether FFmpeg is used.

Regards, Mark