[mythtvnz] VDPAU package can be removed?

Mon May 11 00:52:19 BST 2009

>I get rather weird behaviour with my TV and component out. My TV is a Sony Bravia KLV-40V300A. 
>
>The TV seems to know the difference between a PC and a more typical component like a DVD player.
>
>When I connect using VGA or DVI/HDMI it switches into PC mode. In this mode everything looks the way you'd expect if you pluged >into a standard LCD monitor.  A good chunk of the TV menu options are disabled (Colour, Hue, Sharpness, etc...)
>
>When I connect using Component (or sometimes via DVI/HDMI if I've been messing with nvidia-settings) it seems to switch to a standard >mode, typically 720p, and in this mode the colours are dark and look terrible. Overscan is enabled clipping the edges from the picture.
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>I can only guess that a DVD player has a different colour profile from a PC and the TV is trying to compensate. I suspect if I messed with >the colour setting within nvidia-settings I could make it look right, but that sounds a great deal like hard work.
>
>I did the above testing when I got the TV, so pre-VDPAU, probably around ~173.
>
>Does anyone know if there is a flag I can pass to the video driver to make it look right in this mode?
>Does anyone else see similar issues with different brands/models of TV?
>
>None of the above really worries me as I don't use the component out, but I'm still curious.
>
>Dylan

I have done a LOT of reading and playing around with my system over the weekend, and I believe that I now understand fully what is going on, and also why you’re seeing the behavior you’ve described. Perhaps well known by others, but hopefully educational for a few. BTW, I’ve also got the KLV-40V300A TV. When I look back, I see a few people and given me the solutions early on, I just didn’t recognize them for what they were!

When I first created this thread, I was having 2 problems – judder, particularly evident when watching ticker tapes on news programs, and tearing during playback. I’ve now solved both of these, but have had to make a compromise along the way.

First, this TV supports 1360x768 native resolution, at 60 Hz. At this resolution, I get 1:1 pixel mapping, and absolutely perfect desktop and GUI with no overscan.

The judder is caused by a mismatch between the broadcast refresh rate (25 fps defined by PAL) and the screen refresh rate of 60 Hz. The resulting 3:2 pulldown creates telecine judder. 

http://en.wikipedia.org/wiki/Telecine#Telecine_judder

The solution to this is to run the screen at 50Hz – no 3:2 pulldown, and hence no judder. However, 1360x768 is a VESA format and VESA doesn’t support refresh rates below 60Hz. I confirmed this by looking at the EDID of this TV, and at least according to that 1360x768 50 Hz is not a supported refresh rate. To get 50Hz refresh rate, I need to run at 1280x720 (ie 720p). However (and here’s the compromise) if I do that the TV has the smarts to think I’m now connecting a broadcast device (STB, DVD Player, etc) and turns on overscan and “16-235” studio levels. 

Overscan is a common “feature” of most TVs. (http://en.wikipedia.org/wiki/Overscan) High end, and newer DFPs, often have a feature in their menus to turn overscan off. The Sony Bravia V Series does not.

Colours don’t look natural. Broadcast video uses colour levels in the range 16 – 235, while PCs use a colour range 0 – 255. So my graphics card is sending out video as 0 – 255, however the TV has now switched itself to “broadcast” mode and is interpreting the colours in the range 16-255. Which means, the colours at the top and bottom end of the range are all collapsed together. Darks and lights have lost a lot of definition and contrast. Again, high end TVs often have the ability to allow the user to switch colour modes – the Sony Bravia V Series does not. (Although I did find that going into the TV menu Picture > Advanced Settings > Colour Mode and changing to Wide did help a lot.) The only way (I think) to fix this properly is to get the video driver to scale the colour levels on output. This is something the Windows nVidia driver allows you to do, and I found this post which suggests the Linux driver developers will also support this in future.

http://www.nvnews.net/vbulletin/showthread.php?t=130240

Of course, at 720p I also lose the 1:1 pixel mapping, and the TV scales the resolution up to its native resolution. Which means that the desktop and GUI don’t look as good, although I think video playback looks better. Perhaps the TV’s hardware scaling is better than software scaling?

So all up, where am I now? I’m using HDMI 720p @ 50Hz, and get overscan in the desktop, but the Mythtv GUI and video playback look great after setting the appropriate scaling and X/Y Offsets in the Mythtv Frontend settings menu. Since this is a dedicated Media PC, I’m going to stick with this. Colours look slightly unnatural (although improved after playing with the TV brightness and colours) but most importantly the playback is very smooth. I’m waiting for nVidia to provide a solution to the colours problem. Also, XBMC which I also use supports switching refresh rates, so when playing back NTSC source videos it automatically switches to 60Hz and I get smooth video there too.

I also eventually fixed the tearing problem. Disabled composite according to JYA’s VDPAU FAQ. Interestingly it fixes the problem even when I don’t have VDPAU enabled.

Of course, now I know that ultimately the best solution would be a new TV, but you can imagine how that went down with the wife! Ideally, I need a TV that supports 1920x1080 full HD with 1:1 pixel mapping; at 24Hz, 50Hz and 60Hz refresh rates; the ability to switch on/off overscan; and switch between PC Levels and Broadcast Levels.

I hope all this helps someone.

Aaron

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