[mythtv-users] Hardware for Best TV-Out?

[Flo Kohlert]

> I spent some time looking up the PAL standard and converting that into a
> ModeLine.  I came up with this one, which is nearly perfect in its
> timings:
>     Mode "720x575pali"
> 	DotClock 13.875
> 	HTimings 720 744 808 888
> 	VTimings 576 580 585 625
> 	Flags "Composite" "Interlace"
>     EndMode
> 
> Issues I have yet to figure out:
> - can I use an uneven number of lines in interlaced mode?
>   Will that give me troubles?
> - if I use an uneven number of lines for porch or sync length in vertical,
>   will it alternately use 2 or 3 lines, or will it use 2.5 (PAL
> standard!).
> - the back porch for the horizontal line is a bit too long
>   (5.766us, but it should be between 5.5 and 5.7), but I haven't seen
>   troubles by this.  Everything else is within the PAL specs.
> 
> For those who take interest in the calculations.  PAL standards:
> Line period 64 us (Micro-seconds)
> Line blanking 12.05 +- 0.25 us			Front + Sync + Back
> Line sync 4.7 +- 0.1 us				Sync
> Front porch: 1.65 +- 0.1 us			Front porch
> Burst start 5.6 +- 0.1 us after sync start.	Back porch
> 
> Vblank Start = 2.5 lines
> Vsync Width = 2.5 lines
> Vblank Width = 25 lines
> 
> Horizontal calculations:
> Freq = 13.875 * 10^6 / (625 * 888) = 25Hz (Perfect!)
> line period = 1 / (25 * 625) = 64us (Perfect!)
> front porch = 744-720/888 * 64us = 1.730 us (between 1.55us and 1.75us!)
> sync period = 808-744/888 * 64us = 4.6126s (between 4.6 and 4.8us!)
> back portch = 888-808 / 888 * 64us = 5.766us (too high!)
> 
> Kind regards,
> 
> Mark

Thanks, what does " Flags "Composite" " exactly do?

Thx

flo