[mythtv] DRI/OpenGL vsync

[Tony Houghton]

Hi,

I heard that mythtv could play back interlaced video correctly on a TV
without deinterlacing filters, using X with a PAL- or NTSC-compatible
interlaced modeline by syncing to vblank interrupts provided through DRI
or OpenGL. Previously I thought that was only possible using a Matrox
card with DirectFB, or specialist MPEG decoder cards.

I looked at mythtv's code and borrowed the idea for an embryonic video
player I'm writing. However, I've discovered that the vblank interrupts
occur at 50Hz (for PAL) rather than 25Hz so I don't know how to
distinguish between top and bottom fields. I noticed that the relevant
code in mythtv had lots of stuff concerned with fields, but I found it
difficult to follow and hoped I could avoid that complexity. Can anyone
give me an overview of how it deals with this problem?

-- 
TH * http://www.realh.co.uk