[mythtv-users] Blending/spanning two crt projectors using myth and nvidia nview

[Gene Stapp]

Robert Johnston wrote:
> On 2/21/06, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
>   
>> On 2/21/06, Gene Stapp <genestapp at gmail.com> wrote:
>>     
>>> I checked the archives and couldn't find anything current on this
>>> subject so I'll go ahead and ask.
>>> I currently have two sony vph-1272q projectors. Their maximum resolving
>>> resolution is 660p but 720p looks good albiet a tad soft (I havn't felt
>>> like going through the 12 hour ordeal of totally converging everything
>>> yet since I moved) with a max resolution of 1600x1200... I'm looking at
>>> either horizontally spanning them, which would create a max displayable
>>> resolution of 1200p or rotating them 90 degrees so that my new max
>>> resolution when the two projectors pictures are combined would be
>>> 2400x1600 :)  . Both of these options would use a 16:9 display mode. I
>>> checked with the foremost authority with crt's on this and it is
>>> possible to span them so I am totally stoked...
>>>
>>> I'm going to try this setup with a overclocked 3200+ mobile (to 2.6ghz)
>>> and a 6800gt nvidia card. I looked through the search lists and it
>>> appears mythtv can output spanned content, but is there a performance
>>> hit and would I be better off using xinerama instead of nvidia nview for
>>> the spanning? Is there something I need to do with myth to enable
>>> spanning or does the video card drivers .conf file handle that without
>>> myth knowing. I found some previous threads from 2003 where spanning was
>>> turned off by default.
>>>
>>> Also what is the max resolution anyone has been able to run HD content
>>> in because the sky is the limit with this setup if it works correctly. I
>>> assume with XvMC support turned on the graphics card is the limiting
>>> factor? The HD content would be converted usually from 1080i but some
>>> 720p native movie content would also be used.
>>>       
>> First, since these are front projectors theres no need to go above
>> 1080p for HD content, so 1920x1080p would be the max your going to
>> want to drive with the two in parallel. Running a higher resolution
>> will not do you anything since it will require a processor to upsample
>> the content which is pointless for you.
>>
>> Second, your best bet would be to get some dedicated hardware for
>> this. I know some high end projectors (Runco,etc) have devices for
>> doing this, you might be able to find something that will work with
>> your setup.
>>
>> I've never seen anything for doing this driven from a PC. You'd want
>> to set up a Xinerama with two video cards (two PCI Express cards on
>> one of these new-fangled gaming motherboards), one above the other,
>> both set to 1920x540p and have the two projectors lined up so they
>> make for one fluid screen. Now, whether MythTV would be able to handle
>> using this setup I don't know, but thats the best way I can figure
>> getting it done.
>>
>> I still think a dedicated peice of hardware for this would be the safe
>> way of going about it, if one can be found.
>>     
>
> In thoery you can use NVidia Twinview to handle this. You may
> (However) have to have two seperate cards, as the available bandwidth
> from one card might not be enough.
>
> However, it is rather easy to set up (As long as you make sure you get
> the definitions for each display correct), and if you tell Myth to use
> "All" Xinerama screens (As Twinview announces Xinerama automatically),
> as well as (I think) declaring "XvmcUsesTextures" to get Video
> accelleration using the 3D texture engine, rather than 2D Overlays, it
> should all be perfect.
>
> The REAL difficulty is going to be lining up the projectors and
> balancing the outputs to create a seamless join.
>
> If you do get it running, though, I'd shudder to think what, say, UT
> would look like running at that res. :)
> --
> Robert "Anaerin" Johnston
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>
>   
The hardware option runs around $17k :)  I'm pretty sure I can do this 
through this setup. I think dual SLI might be the only way to go... but 
a quadro card should have no problem driving two 540p screens so I'll 
look at that as an option...
Yeah I think my biggest obstacle is going to be alignment but that is 
doable with the blanking and adjustment options the crt's have... it be 
a lot easier to do with an lcd projector though... thanks for the input 
so far. If I get this working I'll take some high megapixel digital 
pictures and put them up on the web :)