It's my understanding that it is the pixel rate that is doubled to meet the minimum bandwidth requirement of 25Mpixels/sec for hdmi. That is pixels are repeated hence doubling the apparent horizontal resolution. This is always the case for the 480i and 576i modes. The modeline you need should be based on standard EIA/CEA-861B timings like this:
# 1440x576i @ 50Hz (EIA/CEA-861B) ModeLine "1440x576" 27.000 1440 1464 1590 1728 576 581 587 625 -hsync -vsync Interlace
Unfortunately I think there is a special flag that must be set to indicate pixel-repetition is being used and I am not sure how you would get a graphics card to do this. I have not tried using the above modeline so I cannot comment on whether it works. Worth a try though.
There is a good list of EIA/CEA-861B modes here: http://www.avsforum.com/avs-vb/showthread.php?t=947830&page=3 I do know the 720p modeline works on my tv. GTF timings generally don't work for hdmi.
The other issue with interlaced modes is how are the odd/even fields synchronised? Is this the same problem with interlaced output on a good old vga output?
I have often wondered how vdr-xine or xineliboutput would implement dynamic resolution switching. It would be easy to upscale everything to a higher resolution like 1080p. But what if your tv can handle only 1080i at best. It would be better to switch resolution when broadcasts change between 1080i and 720p on a program-to-program basis.
Stuart
--- Ville Aakko ville.aakko@gmail.com wrote:
2008/7/15 Jukka Vaisanen Jukka.Vaisanen@exomi.com:
Well the 100Hz is just a kludge to fit 576i on the
HDMI signaling. My understanding is that the following happens:
PC sends 1-1-2-2-3-3-4-4.. but the a/v receiver
just ignores every other frame because it knows about the 576i kludge also.. so it is just seeing 1+2-3+4 going into the deinterlacer + scaler. The 100Hz thing is just a workaround to get enough data on the link so that the HDMI handshake will happen :P
I'd try to make a modeline:
$ gtf 720 576 50
# 720x576 @ 50.00 Hz (GTF) hsync: 29.65 kHz; pclk: 26.57 MHz Modeline "720x576_50.00" 26.57 720 736 808 896 576 577 580 593 -HSync +Vsync
$ gtf 720 576 100
# 720x576 @ 100.00 Hz (GTF) hsync: 61.10 kHz; pclk: 58.66 MHz Modeline "720x576_100.00" 58.66 720 760 840 960 576 577 580 611 -HSync +Vsync
(if these blow up your 50'' fullHD plasma, you're on your own - try them at your own risk!)
I'd suspect VDR+xinelibout would not support this out of the box. You probably need to make a script or something to change resolutions when needed. Also, xinelibout might not like resolution switches on the fly. But if this is the case, it could probably be worked around by making xinelibout / X part a frontend (I believe this is possible and a very common setup anyways), and restarting it when needed.
OTOH, I don't see much gain in doing the above compared to the deinterlacing in software and then scaling, apart from saving some CPU cycles. I'd doubt any external display could do a better job, though then again, I haven't had any experience with those modern (post-4:3 CRT era TV) displays =)
- Ville
--
Ville Aakko - ville.aakko@gmail.com
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