[mythtv-users] Advice on Building a Quiet MythTV Box?
Paul Gardiner
lists at glidos.net
Sat Nov 29 09:10:38 UTC 2008
Brad DerManouelian wrote:
> I just wanted to clarify for anyone running across this post that MythTV
> does not have a problem displaying beautiful video comparable to what
> you can get from any other system. You either have a hardware or setting
> problem (since you've made sure your settings are all good, I'll go with
> a hardware problem) if it's not as good. MythTV is not the problem.
I've tried three systems:
1) J7F2WE1G2E fanless ITX motherboard, using S-Video out.
2) EN12000E fanless ITX motherboard using component out.
3) A8V motherboard, Athlon64 2.2GHz, Radeon 9000, with VGA
set up to output PAL timings, and wired to TV's Scart.
System 1 wasn't quite as sharp as my DVRs and had washed out
colours. I adjusted colour to 77% and hue to 98%, which improved
the colours a lot, but wasn't perfect. With some content it
can give a really striking picture, but the DVRs still beat it.
Smoothness of playback seems to vary. Most of the time it's
silky smooth, but sometimes it seems to blur more on pans than
the DVRs. I don't believe it's dropping frames, and it isn't
that the interlace fields are getting reversed (that sometimes
happens, and is very visible as edge combs, but can be corrected
by pausing a few times).
System 2. Much better colours without any need for adjustment.
Also sharper. Colours still not quite as good as my DVRs, but
very nearly. Strange problem with certain types of motion.
I don't know what the cause is. Perhaps the VT1625M chip is
doing some unnecessary processing that I can't turn off. Anyway
the motion problem was bad enough that I gave up on this
board and went back to System 1.
System 3 is best of all. Excellent colours. Excellent sharpness.
I can swap back and forth between this and one of my DVRs
sometimes getting confused as to which I'm watching. But it
is this system that led me to claim that MythTV can't quite
perform as well as a good DVR because when I do notice
a difference it's always the DVR that looks a bit better. It's
only very subtle differences. I think it might be that
compression artifacts are more visible. Perhaps that's because
the YUV -> RGB colour conversion is less accurate. I know
colour conversions can amplify compression artifacts. Perhaps
my DVRs use deblocking filters that MythTV doesn't include.
I have no idea really. All I know is I see a slight difference.
As for smooth motion, I haven't tested this system enough to say.
I'm hoping it's as good as the DVRs because it's a system like
this that I'm hoping to move to. I have a Radeon 7000 on order,
which I hope will give the same results as the 9000, but is
low profile and PCI (old style), so will fit any motherbaord.
I've also tried an FX5200 because I hear lots of people use
them. But none of the drivers nv, nvidea, nouveau would output
PAL from VGA correctly. nVidia's own drivers were closest, but
messed up the interlace when using XV (a well known problem)
Apparently it would work if I don't mind going back to a
very old driver, which in turn needs an old Linux kernel.
Admittedly I may not have tried the very latest nouveau drivers.
I've also tried an integrated Radeon X1250. The radeonhd drivers
didn't seem to recognise it correctly, and even driving a normal
LCD monitor it didn't work correctly. I tried ATI's own drivers.
They were much better in the desktop, but MythTv displayed as
a load of random blocks (again a known problem with those drivers
I think).
So, yes, perhaps these are all hardware problems, but it seems
to me there is no good hardware for MythTV to drive SD TVs,
except perhaps ancient ATI cards. Certainly, no one has been able
to suggest anything that will definitely output PAL timings on
VGA, or any other fool proof way to drive my SD TV that will give
results as good as my DVRs. If alternatively it really is settings
then what settings might it be? I have all postprocessing turned
off I believe.
Don't get me wrong. I love MythTV. I couldn't go back to my DVRs
because of the scheduling, and all the other media playback
features it gives. I also like the backend/frontend split. It's
great to have a rock solid recording system.
Cheers,
Paul.
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