[mythtv-users] My MythTV experience

[Ken Bass]

Will, your suggestions were most helpful. I was not aware of the
'deinterlace' checkbox option. I checked that box and there is a world of
difference with the TV-out through the ASUS Pundit onboard SIS chip.
I'm confused that you said the SiS TV Bridge deinterlaces internally. If it
deinterlaces, why would I need to turn playback deinterlace on in Mythtv?
Isn't that happening twice then?

Another thing I did was use the 'sisctrl' utility from www.winischhofer.net
to tweak the brightness and the gamma while looking at livetv and looking at
NTSC color bars.

The result of this trial and error was changes that needed to go into my
/etc/X11/XF86Config file. The changes I made are:

        # [sisctrl] TV related options
        Option "TVStandard" "NTSC"
        Option "SISTVAntiFlicker" "ADAPTIVE"
        Option "SISTVSaturation" "0"
        Option "SISTVColorCalibCoarse" "0"
        Option "SISTVColorCalibFine" "0"
        Option "SISTVCFilter" "true"
        Option "SISTVYFilter" "0"
        Option "SISTVXScale" "0"
        Option "SISTVYScale" "0"
        Option "TVXPosOffset" "0"
        Option "TVYPosOffset" "0"

        # [sisctrl] Xv related options
        Option "XvDefaultContrast" "1"
        Option "XvDefaultBrightness" "35"
        Option "XvDefaultHue" "-4"
        Option "XvDefaultSaturation" "3"

        Option "StoredGammaBrightnessRed" "900"
        Option "StoredGammaBrightnessGreen" "1000"
        Option "StoredGammaBrightnessBlue" "1000"
        Option "StoredGammaPreBrightnessRed" "1000"
        Option "StoredGammaPreBrightnessGreen" "1000"
        Option "StoredGammaPreBrightnessBlue" "1000"

The current CVS ivtv driver is not letting me change brightness, etc. Once
that it fixed, I'm not sure if mythtv will override my settings or not.
These should be settings 'post' the PVR-250 anyhow.

The ASUS Pundit does not have an AGP port so most newer video cards are not
supported. With only 2 PCI slots (hoping to put in 2 PVR-250's) my design
selection of the ASUS was based on it having a decent on board TV-Out.
While the Pundit looks nice, is small, and it quiet--I'm staring to second
guess if the limited expandability is going to bug me.

With the software deinterlacing and the color changes the live tv looks
close to the original broadcast @ 576x480 NTSC-M resolution.

On Mon, 18 Aug 2003 11:54:13 -0400, Will Dormann <wd at pobox.com> wrote:

>>I found that quality changed a lot depending on the resolution I was
>recording at...  Now I know that sounds completely obvious!  However, I did
>find that for example changing the horizontal resolution sometimes made
>HUGE differences to the quality of the whole picture - I'm guessing that at
>certain resolutions the card has to do certain types of processing which
>drops quality
>
>
>I'll second that.   If I record at less than 720x480 (NTSC), the quality
>goes down drastically.  In addition, I remember seeing some "ghosting" when
>using the dnr_* codec options at below 720 horizontal.   I think it's a
>driver bug, but I'm not sure.
>
>Also, play around with the contrast/brightness/colour/hue values in the
>channel table.   (Or I guess it'd make more sense to just monkey with the F
>keys until the picture looks just right, and then update the channel table
>accordingly)
>
>I do agree that the TV-out portion of these kind of machines is the weakest
>link, though.  With the Pundit's TV-out bridge, the signal is deinterlaced
>internally in hardware.   Even though my PVR-250 is recording a full
>resolution interlaced signal, that interlacing is clobbered on output to
>the TV.   (forcing me to enable software deinterlacing in the MythTV setup).
>
>At the time when I was purchasing the equipment to build the machine, I
>decided on a DVD-ROM drive since it wasn't too much more expensive than a
>CD-ROM.   But after realizing the interlacing issues, my Pundit could never
>take the place of a DVD player.   Or even a Tivo, for the same reasons.
>
>I posted a message to the list a little bit back asking about TV-Out
>solutions that preserve interlacing, but didn't have too much luck.  At
>least with respect to cards with TV-out that are supported by Linux.   Some
>mentioned a VGA->RGB converter to connect to a SCART connector, but I"m in
>NTSC land so that's no help.   THere are some external scan converter
>boxes, but those can get expensive, and I've heard some conflicting reports
>on those.  One report said that it was significantly poorer quality than
>the onboard TV-out.   But I'm sure it varies from model to model.    (not
>really a risk I'm willing to take)
>
>Anyway, once you get past the interlacing issues, the quality isn't all
>that bad.  In fact, with the noise reduction options enabled, I find that
>the picture can sometimes look nicer than my TV's built-in tuner.    Just
>play around with the picture adjustments.  I've read somewhere that TV-out
>from computers is generally overdriven.   That is, the signal is too strong
>compared to a regular NTSC signal.  So the picture can look oversaturated
>if not adjusted properly.
>
>Finally, I'm not sure if it's an interlacing issue, a PVR-250 issue, or
>most likely some combination of the both but on my machine the parts that
>look the worse are scenes where there is panning, or if there is a
>scroller/ticker on the screen.   Too jumpy for my tastes.
>
>-WD