[vdr] 576i output on DVI->HDMI?

Stuart Morris stuart_morris at talk21.com
Wed Jul 16 11:08:25 CEST 2008


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 at gmail.com> wrote:

> 2008/7/15 Jukka Vaisanen <Jukka.Vaisanen at 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 at gmail.com
> 
> _______________________________________________
> vdr mailing list
> vdr at linuxtv.org
> http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
> 



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