[mythtv] timestretch: predictive frame skipping (was Re: DVD playback issues, patch)

David Engel david at istwok.net
Wed Nov 25 21:37:07 UTC 2009

On Wed, Nov 25, 2009 at 10:00:42AM -0700, John P Poet wrote:
> The (1x) deinterlacers don't drop half the fields, do they?  Obviously
> the "One field" deinterlacer does, but not the rest, right?  I thought
> the yadif 2x actually worked at a double frame rate, and yadif 1x
> worked at a "normal" frame rate.

My understanding of the regular 1x deinterlacers is that you get one
progressive frame out for every two interlaced fields you put in.
It's called 1x because the frame rate stays the same -- the frames
just get converted from interlaced to progressive.

With the 2x deinterlacers, you get 1 progressive frame out for every
interlaced field you put it.  It's called 2x because it effectively
doubles the frame rate -- 30 interlaced frames become 60 progressive

I could be wrong, but I thought it was because of the rate doubling
deinterlacers and timestretching that Daniel(?) added the fallback
deinterlacer support.  I believe the intent was to make sure the
effective frame rate was always less than the display's refresh rate.

> With a playback of 1.2x. Myth would end up "extending" a lot of frames.

Yes.  So?  It seems to work acceptably well IME with interlaced
content.  I'd just like to see it work as well with progressive

> I don't know what the best solution is.  I will probably tinker with
> this tomorrow and see.

I don't know the best solution either.  I'm just throwing out an idea
in case someone is more know knowledgeable and motivated enough to try

David Engel
david at istwok.net

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