Intel GMA 900 (915G) - interlaced modes?

Krzysztof Halasa khc at
Tue Jan 9 12:44:57 PST 2007

"Will ." <nodenet at> writes:

> I avoid doing any testing on
> my computer LCD display as I've found the results to be missleading
> (even using the same resolution and refresh rates - the nature of the
> displays is different anyway).

Sure, progressive display mode.

> I've been running on the VGA ouput at 720x576 @49.986.. (the closest I
> could get to 50Hz without the TV encoder).

Progressive, I assume - EPIA (CLE266) can't do interlaced (or nobody
knows how) on VGA out. That's way I'm switching to i915 - I want the
PC to send it "as is".

> Full frame straight into
> the VGA input on the plasma. Results are generally very good, although
> it took alot of tweaking and messing to get there. I encountered some
> problems sending video at 50frames per second (using software
> de-interlacing) when I'm only displaying circa 49.99,

That IMHO shouldn't be a problem, it should sync anyway.

> I've not had any luck with the field parity, I have to run with the
> software deinterlacer to get interlaced video working
> smoothly.

Sure. With interlaced mode out of CRTC (instead of TV-out encoder)
there are no such problems (i.e., no "by luck" things and no constant
switching due to lost IRQs, the fields can be swapped but that's
a matter of a single switch - PAL (analog, not DV) normally uses
top-first, CRTC may do bottom-first as with NTSC).

Anyway, with interlaced CRTC mode you basically sync to 25 or ~30 Hz
and things work automatically.

> I
> think there may be a fix for the field parity on the EPIA although I'm
> not sure if it works under X or not, and I think scart out from the TV
> chip on the EPIA requires a soldering iron too.

Actually I need to use VGA out, SCART (RGB) is the TV input (no VGA in).

> If you get the
> interlace modes working it would probably make the VGA out a good way
> to go to get scart, althought I think you'll still need to run with a
> software deinterlacer to get things working.

No, the only deinterlacer needed is in the TV (not sure if a 100 Hz CRT
TV monitor needs to deinterlace).
Krzysztof Halasa

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