[mythtv] Ideas for high quality TV-out

[Robert-Paul Berretty]

On Mon, Jun 28, 2004 at 11:32:44PM +0800, Michael Wright wrote:

> Hi Doug,
> 
> Thanks, that is a very informative response.
> 
> I would be very interested in getting hold of your patch. 
> 

[snip]

> I also intend to look at the nv driver to see if it supports VSYNC in
> anyway. I'm guessing no because it seems to be a Kernel level thing. 
> and X is purely user-space.

I've been working on getting interlaced video playback smoothly for a while
now. I've got a PVR 250 backend, and an XBox frontend. So far for nVidia
binary drivers. 

The PVR 250 spits out interlaced MPEG2. I've managed to get the video out 
(Conexant) to align with the frames in the framebuffer.
Consequently, the video out alternatingly renders the odd, and the 
even lines. This effectively means that I've got 50% chance of having
correct playback. The other 50% is 'inverse interlaced' playback (jumping
back and forth in time, major GAF penalty ;-).

I've been looking at the sources of recent nv drivers. There is an XV
option called XV_SYNC_TO_VBLANK, but I haven't been able to port all of
the XBox specific patches to the nv driver. So, I cannot share whether
this would help you sync on a frame iso a field swap. I'd be happy to know,
since that would give another incentive to get the latest driver to work.

> > I actually had a 'bob' deinterlacer (display fields sequentially) 
> > working in my private development tree for a time, but haven't carried 
> > it forward for three reasons:

As for the 'bob' deinterlacer, depending a bit on the scaler that you'd
use, I do not think that this is going to really solve the problem without 
a frame blank sync. My guess would be that if you're displaying an odd
frame at the even 'phase' of the video out, the playback would be shaking
up and down at a rate of 50fps. Perhaps Doug can share how he solved this,
since a solution there would also work for the XBox setup. 

> > I'm willing to share the code I came up with for these tasks, though 
> > it's against a CVS that's several months out of date.

Pretty please, sugar on top.


RP