[mythtv-users] My MythTV experience

[Will Dormann]

>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