[mythtv-users] New deinterlacer for perfect image quality when using an interlaced display, mode that matches the source

Tom Dexter digitalaudiorock at gmail.com
Mon May 11 19:38:40 UTC 2009

On Thu, Mar 26, 2009 at 8:26 AM, Paul Gardiner <lists at glidos.net> wrote:
> I've just created a patch that provides a deinterlacer for perfect image
> quality and motion smoothness when using an interlaced display mode that
> exactly matches the video source. See Ticket #6391. The deinterlacer comes
> up in the menus as "Interlaced x2". It is also known as field order.
> Preconditions of use
> ~~~~~~~~~~~~~~~~~~~~
> You need a graphics chip that can output interlaced display modes correctly.
> The display mode must be interlaced exactly matching the video source.
> No scaling can be used: don't use scaling to reduce overscan.
> Video playback must be full speed, not sped up or slowed down.
> The deinterlacer is a doublerate one, so you may need the patch from
> Ticket #2903 before MythTv will allow you to use it.

I discovered today that the 0.21-fixes version of the bug 2903 patch
didn't work correctly, as I've explained in the additional comments.
My refresh rate of 30.0267 was failing that test and thus not getting
doubled when I used this version of the patch.

However here's what really confuses me:  When I attempted to watch
recorded 1080i content, it was rejected the fieldorder deinterlacer
(as you'd expect with the above check) and therefor using none.
However...when I watched 1080i LiveTV, for some reason it was allowing
the fieldorder deinterlacer, but was completely whacked out.  I think
perhaps it may have been trying to use it without treating it as line
doubling deinterlacer, though there's a lot going on there I'm not
familiar with at all.  In any case, that was the cause of the
nightmare I went through trying to upgrade to a newer rev of fixes as
described here:


I didn't realize when I posted that that pre-recorded 1080i was using
no deinterlacing at all, which was why it didn't encounter those
errors.  With LiveTV it never thought the video had caught up.

Again, I'm very unclear on exactly what that did...but LiveTV was
allowing the fieldorder deinterlacer even when the 2903 patch wasn't
correctly doubling the rate, and the results were pretty ugly.

Once I got that patch corrected, rev 20500 is working perfectly for me.


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