[mythtv-users] Nvidia 720x480 troubles

Shawn Asmussen asmussen at cox.net
Mon Aug 9 01:32:44 EDT 2004

I upgraded to the new 6111 driver today, which went fairly smoothly. If I
exit the X server, the text mode console looks garbled, but I don't really
care about that, since obviously the box will be running in graphical mode
pretty much all of the time.

I took the opportunity to try and get 720x480 resolution working. I hadn't
been able to do it with the driver I was using before, and after fiddling
around with it some more today, and trying a new modeline that I found, I
got it to work. (The previous NTSC 720x480 modelines that I had found on
the internet caused the X Server to complain that the hsync was out of
range, when I tried them with the 6111 driver.)

Mythtv looked fine when it first came up under 720x480, although there is
a little bit of unused screen at the top, which from what I understand I
may be able to tweek using tools that come with the driver. I haven't
tried that yet. Other than that little bit of space at the top, the mythtv
menus fill the entire screen. When I watch a recording or live TV it's not
so great. It works, but there is a significant amount of unused space at
both the left and right sides of the screen, and the picture appears
slightly squashed. This is not a case of the video card output failing to
fit the screen. If I wiggle the mouse around, when it gets to the edge of
the screen the mouse cursor becomes visible, and its location is at the
edge of the TV screen, not where the playback picture stops. It seems that
although the X server is displaying at 720x480, mythtv is only using the
middle 640 columns for playback, although it uses the full available
resolution for menus. When watching live TV, and I pull up the program
guide, I also notice that the black empty space on either side of the
picture shows up in the preview window also, although I'm not sure exactly
why that is.

I'm using a PVR-350, and a PVR-250 in my box (Not using the TV-out on the
350 at this point obviously). I have the recording profiles setup to
record at 720x480 on all of the profiles. My understanding was that by
running the X server at 720x480, I would get the best results because then
the video would not need to be scaled to the resolution of the X server.
However, it seems to be getting scaled to 640x480 anyway. If it's
relevent, 640x480 was the resolution I was using before I made the switch
to 720x480. The only thing that even comes to mind is that mythtv is
rescaling it because 720x480 isn't a 4:3 ratio. If that is the case then,
I don't understand why 720x480 would be a desirable resolution to capture
at, or to run on the X server. If mythtv will force the final output to be
4:3 scaled, then wouldn't it be better to just capture the video at
640x480, and run in 640x480 resolution?

I've tried looking through the archives to get a handle on this, but all
I've learned for sure is that I don't really completely understand all of
the issues involved with using different resolutions. If somebody can help
clarify this for me, I'd really apprecitate it. My end goal is just to
aximize the quality of my TV out. Most of what I have seen suggests to me
that 720x480 is the best resolution to capture at with the Hauppauge card,
and both common sense, and a few things I have read in posts to the list
suggest that anything you can do to eliminate having to scale the image is
good. Unfortunately for me, those two ideas don't seem to be meshing with
each other very well on my system, and I'm not sure if it's just an issue
of getting the settings right, or if some of my fundamental assumptions
aren't sound. HELP!

Shawn Asmussen

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