[mythtv-users] HD deinterlacing

[Phil Vid]

On 10/1/07, Mark Kendall <mark.kendall at gmail.com> wrote:
>
> Are you using opengl-vsync as well?

I recompiled afterwards - didnt realise it was a compile option and
thought the mythtv-vid branch had somehow taken the option off the
menus.
Unfortunately once I had rebuilt enabling opengl-vsync in the menu
made the display completely corrupt, no video would play back at all.
Will try more debugging with this tonight to see if I can work out
what causes this.

> Linearblend does not double the frame rate when it is deinterlacing.
> Hence you only get 25 frames per second. Using a 'frame rate doubling'
> deinterlacer (e.g bob) will give you much smoother playback.
>
> You also need to ensure that you have the appropriate display refresh
> rate. So assuming you live in PAL land, you need to be running a
> 1080p50 modeline to best match PAL sources (25 fps) to the display.

Adjusted to 50hz, seems to be a significant improvement.

> You will get some vertical 'jitter' with bob  - that's the nature of
> how it works. It shouldn't however be too noticeable if your display
> refresh rate is 'matched' to your source.

The HD 1080i content makes the jitter significantly less noticeable.
With lower quality content I've turned on linear blend as bob made it
almost unwatchable.

> The speed issue might be a symptom if you are not using opengl-vsync.
> > You could also try opengl linearblend (2x HW) or opengl onefield (2x
> HW) - but I suspect your graphics card isn't up to it.

Will try this later this evening as well.

> The best solution would almost certainly be to use a 1080i modeline
> for 1080i material (use xrandr if need be) and get the tv to
> deinterlace for you.
> If you're lucky, your tv will just sync with the incoming interlaced
> material otherwise try the 'Interlaced' opengl deinterlacer which is
> designed for this situation. It's a less gpu hungry filter so may just
> work with your card.

And another follow up here - the nvidia card seemed to think 1080i
would require 100.1 hz to display and was rejecting the mode.
Does xrandr 'just work' when you have the correct modelines or do I
need some additional config?

> Regards
>
> Mark

Thanks for the quick and very detailed reply. It has helped a lot.

Phil