[mythtv-users] Nvidia picture size (SVIDEO)

[Mark Smith]

In message <6a50404e05050412187d0e910f at mail.gmail.com>
          Mark Howells <mark.howells at gmail.com> wrote:

> I'm starting to make progress now with my mythtv box :)  So much so
> that I've been using it on my TV - even watched a movie last night. 
> Anyhow,  the TV image is small and whatever I do to try and change it
> appears to have no effect.  The basic X screen appears as 4:3 (or so
> it seems) and seems to fill the screen vertically.  It's a widescreen
> TV so I expect black borders down the side.  However, when I switch to
> watch TV (or a recording playback) I get a widescreen image
> letterboxed into the 4:3.  None of the settings I have tried appear to
> make any difference.  I seem to be so near yet so far.

One way to achieve the desired effect is to entire a line into your xorg.conf
something like:

DisplaySize 400 225

This tells X that you have a 16:9 display, which both Myth and Xine will use
as an indication that 16:9 programmes should fill the screen and 4:3
programmes should have vertical black bars either side.

If have a Monitor section which defines the setup for my PAL TV, primarily
for UK DVB-T which tends to use 720 x 576 and 704 x 576 video resolutions:

Section "Monitor"
        Identifier   "TV0"
        VendorName   "Toshiba"
        ModelName    "28 inch widescreen"
        HorizSync    15.625
        VertRefresh  50
        ModeLine     "704x576" 13.625 704 728 792 872 576 581 586 625 -hsync -vsync interlace
        ModeLine     "720x576" 13.875 720 744 808 888 576 581 586 625 -hsync -vsync interlace
        DisplaySize  400 225
EndSection                                                                   

I then have a screen defined which uses this monitor definition. Note that my
system is currently complaining about the 704x576 mode - not sure if that's
because it is incompatable with the SVideo out in some way.

This definiton additionally sets up the VGA output such that you can feed an
RGB signal into a SCART connector if you build a simple sync convertor
circuit - something I have yet to do, but should give much better results.

I am getting reasonable results with my GeForce 5200 (NV34) card, though
movement of scrolling text in particular is not 100% smooth. The RGB out
should fix that problem (as the output is then field for field is it was
intended to be viewed). I believe some people are getting good SVideo results
with a combination of Bob deinterlacing and the OpenGL vsync support - I
believe the latter has to be specifically compiled into Myth, though.

> I'm using a Geforce MX4000 and driving the TV via SVIDEO.  The picture
> quality seems OK for LiveTV but really grainy and flimmery
> (interlaced?) for text and the X windows herringbone background.

A lot of people have reported poor SVideo output on NV18 nVidia cards. If you
check your Xorg.0.log file what does it say you have?

-- 
Mark Smith - Surrey, UK
http://www.chez-moi.org.uk/