[mythtv] [mythtv-commits] Ticket #2429: Autodetect video scan is confused by 1080i recordings

[Isaac Richards]

On Wednesday 20 September 2006 5:24 pm, Jack Perveiler wrote:
> <snip>
>
> > > It's not wrong.  It's reporting based off of what's in the video
> > > headers.
> >
> > I see. And 0.19 did not look into the video headers?
> >
> > So, it's the fault of the channels or the provider.
> >
> > In that case, it would be extremely helpful to have a setting to force
> > this always to "interlaced" (for 0.20 fixes branch).
> >
> > BTW, what's the negative effect, if I set a progressive recording to
> > video scan "interlaced"?
> > I can see no negative effect here, so maybe this means all my recordings
> > really are interlaced, but some are wrongly marked in the video headers?
>
> Deinterlacing, at least with bob, can have some very undesirable side
> effects when used with progressive content.  In my case I see two copies of
> every image: one squished into the top half of the screen, the other
> squished into the bottom half.  I don't know if that's what happens for
> everyone, but that's what happend for me.

Well, that shouldn't be happening.  Sounds like the bob filter's in place, but 
it's not doing the proper output..

> Which is why I thought the ability to change the default away from "detect"
> on a  per-channel basis sounded interesting.  Isaac, any comment on that? 
> If I coded it up, is the idea something that could be committed?  It sounds
> like it won't fix everything for everybody, but could help some (myself,
> anyways) and could still be overridable by the OSD selection.  I don't want
> to waste my time on something non-commitable, though.

I dunno if I like the idea of another setting for this.  Be better just to 
improve the handling of these situations.

For instance, see NVP::AutoDeint(VideoFrame *frame)..  It's only going to flip 
between interlaced/progressive after a couple frames of the opposite type to 
what's current have been seen, instead of on the actual frame that needs it.  
That'll lead to a couple frames of interlaced content being displayed as 
progressive, etc..

Other thing to add would be automatic detection of telecined content (by the 
flag pattern, most likely), and automatically turning on the ivtc filter as 
necessary.

Isaac