[mythtv-users] Bad TV picture quality on an HDTV

[Brad Templeton]

On Thu, Jan 20, 2005 at 09:49:54AM -0700, Matt Grommes wrote:
> Hi, I'm new to myth and thanks to Jarod's guide I've almost got 
> everything set up, except for the main use of the system: regular TV. 
> I've got a Toshiba HDTV that says its native modes are 720p and 1080i. 
> After _much_ tweaking I finally got a useable desktop on 720p where I 
> can see everything in KDE and in MythTV but my TV picture quality is 
> terrible. I have a wintv 250 and digital cable through Comcast. When I 
> plug the same svideo cable from the cable box into my TV, it's perfect. 
> The picture in myth seems very pixellated and there's a lot of "banding" 
> where colors touch each other. It's similar to a badly encoded mpeg or a 
> small video clip stretched to full screen. Is the 1136x670 resolution of 
> my desktop causing the TV to stretch or something? I've tried a lower 
> 800x480 540p resolution and it seems the same. I'm recording in 720x480 
> with (I think) 4500 bit rate of encoding. I'm almost totally ignorant 
> when it comes to X modelines and things so just getting the useable 
> desktop at 720p was a feat. When I try a smaller 540p resolution a lot 
> of the screen goes off the edges of the TV until I run nvidia-settings, 
> then it shrinks the screen until it's like a 20" picture in the middle 
> of my 32" TV. The nvidia-settings was how I finally got the 720p 
> resolution to fit on the desktop. When I play a video or a DVD, it looks 
> great. It's only TV that looks bad. Sorry for the rambling but I'm at 
> the limits of my knowledge.

Yes, this happens.  I am not sure of the cause yet.  The HDTV is "too sharp"
and you see all sorts of mpeg artifacts on the screen, but it looks much
better on a regular TV with TV-out.

Some suggestions to play with:
    a) Turn off all the stupid "edge enhancer" and "sharpening" found in
    many HDTVs.   They are treating the mpeg artifacts as real things and
    enhancing them.

    b) If nothing else works, plug the svideo into your hdtv and see how
    that does.   It would mean, annoyingly, you would have to switch
    inputs (and change resolutions with randr) to watch SDTV shows.

    c) And yes, record at even more than 4500 bps

    d) Finally, consider trying some smoothing filters on the myth
    filter page.   Unfortunately, I don't know if you can yet configure
    different filters for different resolutions, since you definitely don't
    want those filters on your HD content.