On Tue, Jan 06, 2009 at 01:17:52AM +0200, Jukka Vaisanen wrote:
Yes, it's a good idea to get 1:1 pixel mapping on your display. Double scaling (first pc, then display) is not a good idea, ever.
But, some problems arise:
HDMI uses DVI signalling for the video (and audio is hidden in a vertical blanking time slot believe it or not) so it may seem like just another connector.. however in their finite wisdom the HDMI standardization people decided that HDMI will not support arbitrary resolutions, but instead only the existing (and back then, planned) broadcast resolutions:
576i/p (pal) and 480i/p (ntsc)
720p (1280x720)
1080i and 1080p (1920x1080)
The world is full of TVs with 1366x768 and other weird resolutions. There are also plasmas with 1024x768 etc "standard computer resolutions". The big surprise to many people is that even though DVI signalling could carry these native resolutions, the displays themselves won't accept / sync to them. And they don't advertise them in the EDID data so you have to force your computer to that resolution / refresh to even try it (and fail).
The only true 720p displays I have seen are rear-projection TVs and data/av projectors. They will accept their native resolution of 1280x720 over HDMI, however getting rid of overscan to get 1:1 is another matter..
Then a solution:
I used to have a Panasonic plasma with a similar non-standard resolution and I used the VGA port with it to automatically get a 1:1 pixel display as it's intended for PC display use. Yes VGA is not optimal but at that resolution and a 1 meter cable, who cares... Today I have a full HD 1920x1080 panel with an option for "exact scan" which gives me 1:1 pixels (without overscan) out of the box over HDMI, I just run normal 1920x1080@60Hz out of my computers.
And finally a question:
If someone can tell me how to get 576i over HDMI out from VDR, please do. That way I could use my external HQV Reon video scaler to upscale it.. Of course it would need to allow me to switch modes for 720p and 1080i also based on broadcast resolution ;)
Hello.
Please check this thread: http://www.linuxtv.org/pipermail/vdr/2008-July/017347.html
Original patches: http://lowbyte.de/vga-sync-fields/
New version: http://www.vdr-portal.de/board/thread.php?threadid=80567
Those might help.. they're about getting pure 1:1 interlaced (576i) RGB output from a VGA card.. and the new version also has some HDTV stuff, I guess. I don't read german so i'm not familiar with that..
There are also patches to maintain perfect field sync to DVB stream to avoid tearing/stutter/jerkiness.
-- Pasi