[Openchrome-users] TV Resolution problems

[Chad]

On 4/5/06, Steffen Schumacher <steffen at schumacher.dk> wrote:
> Hi!
>
> I'm not really too much familiar with either linux or PAL/NTSC stuff,
> so please forgive me for ignoring the obvious..

Generally speaking:
PAL = European Standard (and others)
NTSC = US/Japan Standard (and a few others?)

> I'm wan't to build a MythTV box using a via M10000(CLE266) and a PVR-150.
>
> I seem to have several problems:
> 1. CPU problems when decoding 720x576 mpeg2 ( unscientific top says ~ 100% cpu )

Decoding with what application using which output?  Mplayer using xv
or mythtv using "standard","libmpeg2","Standard XvMC", "Via XvMC"?

> 2. Resolution - Using mode 720x576Noscale, the picture doesn't fit onto the screen?

Doesn't fit how?  Offset to one side, too big (zoomed?), too little
(black box all around the image)?

> I've pulished xorg.conf and Xorg.0.log at http://131.164.191.12/xorg.conf and
> http://131.164.191.12/Xorg.0.log
> I'm running FC4 with a recent 'yum -y update', so I should have pretty much
> updated stuff in there I think..
>
>
> 1.
> This is probably the most important. I think I should have enabled libVIAXvMC.
> It should be enabled in mythtv and in xorg. (please look at xorg.conf and Xorg.0.log)
> I'm missing some way to test if it is actually beeing utilized?

How is MythTV installed, via the source from mythtv.org or via RPM's
from somewhere like Axel's Repo (ATRpms)?  If it's via the source, you
should be able to duplicate the configure step to see if the
libviaXvMC was found or something else.  If you are so inclined and
lucky, you will see libXvMCW which is the wrapper script, in which
case means you simply have to place the name of your via XvMC lib in a
file.  So, if your XvMC lib (located in /usr/lib) is something like
libviaXvMC.so.1 then you would:
echo libviaXvMC.so.1 >> /etc/X11/XvMCConfig
And then start up mythtv, go to your playback setting, change the
output to ViaXvMC (or even regular XvMC) and then try to watch an
mpeg2 file.  See what the output in your mythfrontend log says (start
it from an xterm so you can get instant feedback by switching focus to
your xterm while the mpeg2 is playing back).

> All I'm seeing in Xorg.0.log is (II) VIA(0): [XvMC] Initialized XvMC extension.

That's good news.

> Should I do something other then simply enabling it in mythtv?

Well, maybe.  Depends on your configure step above as mentioned. 
Should you want to hard code (I'm a fan of the wrapper library
personally) the library, you could force mythtv you use your via XvMC
library instead of the XvMC Wrapper.  If the configure script doesn't
attach directly to your lib, you can edit the configure options that
were created from the configure script to hard code the path of the
XvMC library, though I don't recommend it.

> how can I test it?

If it's the wrapper, but starting mythtv, changing your output,
watching a show and reading your xterm's output.

> 2.
> I think mythtv supports scaling the signal to a given size, so if i'm screwed,
> I'll probably fall back to tweaking mythtv to only output to the visible parts
> of the screen. However I've gotten the impression that scaling yeilds bad performance
> and / or quality.

Not sure how you'd be screwed, but yes, MythTV does allow you to set
the desired output size for TV playback versus GUI size.  Check in
your Settings under Appearance, you will see seperate size for GUI and
TV, adjust those numbers to your hearts content.  My understanding is
that scaling is done by your CPU, so it will eat CPU cycles if you
aren't outputting at the same resolution as the original content was
recorded at; I think it's not as CPU intensive as one would think, but
defintely chews a few.  Quality is probably close if not the same as
long as you aren't scaling too much bigger than the recorded
resolution (and your CPU isn't taxed).  If you are down scaling then
you'll probably get at least as good of an image as the original
recording (assuming it was done in mpeg2 and not in analog compressed
to mpeg2).

> So I would like to be able to make all pixels visible on my screen to avoid this,
> but I don't really know where to start?
> If I use 640x480 resolution, it fits neatly.

Are you sure your source material has a 720x576 resolution?  I usually
run mplayer to check that my resolution is what I think it is.  If
640x480 fits the best, you probably have source material at that
resolution or close to it.  If you are sure it's 720x576, make sure
Myth isn't scaling it down before outputting to your TV or Monitor.

> I'll post the output of xdpyinfo and xvinfo to respectively:
> http://131.164.191.12/xdpyinfo &
> http://131.164.191.12/xvinfo
>
> in about 3-4 hours (when I get home to the box ;o) )
>
> Please ask me anything you need.
>
> /Steffen
>
> _______________________________________________

The only thing I can think of that hasn't been posted would be your
configure output from MythTV.  The only other thing I can think of is
to tell us what you are driving (what is your display device), it
might help us to suggest a resolution.

HTH

Chad