[mythtv] updated FAQ submitted for your approval

Chris Kleeschulte mythtv-dev@snowman.net
Thu, 15 Aug 2002 20:02:11 -0700


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 MythTV FAQ

) My mouse pointer disappears over the windows?
- This is desired behavior.  The interface is meant for use with a =
remote control, or a keyboard.

) What's this 'strange error flushing buffer' mean?
- Nothing, really.  It's just lame (the mp3 encoder) complaining for =
some obscure reason.

) The audio's _really_ out of sync, and it doesn't pause when I pause =
live TV?
- You need to mute the line-in, and set the mixer to record from the =
line in. The audio you're hearing is from the audio pass-through, =
enabled by the V4L driver, and not MythTV.

) I get an error when compiling about 'mkspecs'?
- You need to set QTDIR.  On Debian, it should be /usr/share/qt On =
Mandrake, it should be /usr/lib/qt3

) I can't change the channel when watching TV?
- Something's wrong with your program database.  Did filldata run with =
no major errors?

) I want to run the database on another machine?
- Ok, first, you'll need to edit the mc.sql script first to setup the =
proper permissions for the machine that'll be running mythtv and =
connecting to the database.  Next, after you've followed all the =
directions and built all MythTV's programs, and after you've done a make =
install, but before you've run filldata, you need to edit the =
/usr/local/share/mythtv/mysql.txt file to it points to the server you're =
running the mysql on.  If you want, you can copy that mysql.txt file to =
~/.mythtv/.  If it's in ~/.mythtv/ then it won't get copied over by =
another, future, 'make install'.  Once that's all done, you should be =
all set, I think.

) Is it currenlty possible to have MythTV change the channel on my cable =
box, instead of my tuner? The reason I ask is because I have digtial =
cable, however I only have a analog WinTV tuner card in my PC.
- Yup, see here:

http://www.snowman.net/pipermail/mythtv-dev/2002-July/000020.html

Essentially, most of the code's there for it, it just needs someone that =

actually wants the feature to finish it up.

) Which TVOUT card are people using?
- I'm using a Gainward Geforce4 Ti4200, but any card that has Xv support =
in=20
Xfree should work just fine.

) The "Tv Guide" function...does it only work in UK?  I'm gonna be =
travelling, but not that far.  :)
- No, the tv guide is xmltv =
(http://www.doc.ic.ac.uk/~epa98/work/apps/xmltv/). It current works in =
the US, Canada, UK, Germany, and Austria.

) I was also wondering if there is a specific reason a hardware =
encoder/decoder is not used?
- Well an encoder/decoder would be more efficient, but most of them are =
closed source requiring reverse engineering to build a driver. There is =
this one=20
(http://www.linuxtv.org/mpeg2/kfir.xml) if you're so inclined to =
integrate it into mythtv.

) First of all, I have gathered that you are using X11 and the Xvideo =
extension for your output.  How do you control flipping the images of a =
video stream from one frame to the next such that they only get flipped =
on the vertical retrace (vsync pulse).  As I understood it, this was not =
possible in X11/Xv.  If you can't do this, then you must get horrible =
tearing of your displayed video streams.
- Actually, I only see very minor tearing when using a monitor as a =
display device, and that very rarely.  On a TV as an output device, none =
at all. XvPutImage with a call to XSync immediately after seems to =
automatically sync up with the retrace.  The video output code does make =
its best attempt to display frames at exactly the right times, which =
also helps. =20

) I have also gathered that you are using the Nuppel video format.  I =
have not really looked much into this format myself, but does it store =
field information (i.e. interlaced streams) or is it progressive like =
MPEG1 and store frames?  If it's progressive like MPEG1, how do you deal =
with the temporal issues of two fields, each being a different snapshot =
in time being combined together into a single frame?  Do you get =
interlace artifacts or does Nuppel have some =
smoothing/blending/interpolating" algorithm to combine the two fields =
into a single frame?
-I've got code in there to deinterlace the image (grabbed the linear =
blend filter from mplayer), but that's only needed when displayed on a =
monitor --=20
the tv out (at least with nvidia's drivers) does the right thing and =
separates the frame into its fields for display.


end-------------------------------end


thanks,
Chris

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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DVerdana size=3D2>&nbsp;MythTV FAQ</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) My mouse pointer disappears over =
the=20
windows?<BR>- This is desired behavior.&nbsp; The interface is meant for =
use=20
with a remote control, or&nbsp;a keyboard.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) What's this 'strange error flushing =
buffer'=20
mean?<BR>- Nothing, really.&nbsp; It's just lame (the mp3 encoder) =
complaining=20
for some obscure reason.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) The audio's _really_ out of sync, =
and it=20
doesn't pause when I pause live TV?<BR>- You need to mute the line-in, =
and set=20
the mixer to record from the line in. The audio you're hearing is from =
the audio=20
pass-through, enabled by the V4L </FONT><FONT face=3DVerdana =
size=3D2>driver, and=20
not MythTV.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) I get an error when compiling about =

'mkspecs'?<BR>- You need to set QTDIR.&nbsp; On Debian, it should be=20
/usr/share/qt On Mandrake, it should be /usr/lib/qt3</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) I can't change the channel when =
watching=20
TV?<BR>- Something's wrong with your program database.&nbsp; Did =
filldata run=20
with no major errors?</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) I want to run the database on =
another=20
machine?<BR>- Ok, first, you'll need to edit the mc.sql script first to =
setup=20
the proper permissions for the machine that'll be running mythtv and =
connecting=20
to the </FONT><FONT face=3DVerdana size=3D2>database.&nbsp; Next, after =
you've=20
followed all the directions and built all MythTV's programs, and after =
you've=20
done a make install, but before you've run </FONT><FONT face=3DVerdana=20
size=3D2>filldata, you need to edit the =
/usr/local/share/mythtv/mysql.txt file to=20
it points to the server you're running the mysql on.&nbsp; If you want, =
you can=20
copy that </FONT><FONT face=3DVerdana size=3D2>mysql.txt file to =
~/.mythtv/.&nbsp;=20
If it's in ~/.mythtv/ then it won't get copied over by another, future, =
'make=20
install'.&nbsp; Once that's all done, you should be </FONT><FONT =
face=3DVerdana=20
size=3D2>all set, I think.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) Is it currenlty possible to have =
MythTV change=20
the channel on my cable box, instead of my tuner? The reason I ask is =
because I=20
have digtial cable, however </FONT><FONT face=3DVerdana size=3D2>I only =
have a=20
analog WinTV tuner card in my PC.<BR>- Yup, see here:</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2><A=20
href=3D"http://www.snowman.net/pipermail/mythtv-dev/2002-July/000020.html=
">http://www.snowman.net/pipermail/mythtv-dev/2002-July/000020.html</A></=
FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>Essentially, most of the code's there =
for it, it=20
just needs someone that <BR>actually wants the feature to finish it=20
up.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) Which TVOUT card are people =
using?<BR>- I'm=20
using a Gainward Geforce4 Ti4200, but any card that has Xv support in =
<BR>Xfree=20
should work just fine.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) The "Tv Guide" function...does it =
only work in=20
UK?&nbsp; I'm gonna be travelling, but not that far.&nbsp; :)<BR>- No, =
the tv=20
guide is xmltv (<A=20
href=3D"http://www.doc.ic.ac.uk/~epa98/work/apps/xmltv/">http://www.doc.i=
c.ac.uk/~epa98/work/apps/xmltv/</A>).=20
It current works in the US, Canada, UK, Germany, and =
Austria.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) I was also wondering if there is a =
specific=20
reason a hardware encoder/decoder is not used?<BR>- Well an =
encoder/decoder=20
would be more efficient, but most of them are closed source requiring =
reverse=20
engineering to build a driver. There is this one </FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2>(<A=20
href=3D"http://www.linuxtv.org/mpeg2/kfir.xml">http://www.linuxtv.org/mpe=
g2/kfir.xml</A>)=20
if you're so inclined to integrate it into mythtv.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) First of all, I have gathered that =
you are=20
using X11 and the Xvideo extension for your output.&nbsp; How do you =
control=20
flipping the images of a video stream </FONT><FONT face=3DVerdana =
size=3D2>from one=20
frame to the next such that they only get flipped on the vertical =
retrace (vsync=20
pulse).&nbsp; As I understood it, this was not possible in X11/Xv.&nbsp; =
If=20
</FONT><FONT face=3DVerdana size=3D2>you can't do this, then you must =
get horrible=20
tearing of your displayed video streams.<BR>- Actually, I only see very =
minor=20
tearing when using a monitor as a display device, and that very =
rarely.&nbsp; On=20
a TV as an output device, none at all. XvPutImage with a call to XSync=20
immediately after seems to automatically sync up with the retrace.&nbsp; =
The=20
video output code does make its best attempt to display frames at =
exactly the=20
right times, which also helps.&nbsp; </FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>) I have also gathered that you are =
using the=20
Nuppel video format.&nbsp; I have not really looked much into this =
format=20
myself, but does it store field </FONT><FONT face=3DVerdana =
size=3D2>information=20
(i.e. interlaced streams) or is it progressive like MPEG1 and store=20
frames?&nbsp; If it's progressive like MPEG1, how do you deal with the =
temporal=20
</FONT><FONT face=3DVerdana size=3D2>issues of two fields, each being a =
different=20
snapshot in time being combined together into a single frame?&nbsp; Do =
you get=20
interlace artifacts or does Nuppel </FONT><FONT face=3DVerdana =
size=3D2>have some=20
smoothing/blending/interpolating" algorithm to combine the two fields =
into a=20
single frame?<BR>-I've got code in there to deinterlace the image =
(grabbed the=20
linear blend filter from mplayer), but that's only needed when displayed =
on a=20
monitor -- <BR>the tv out (at least with nvidia's drivers) does the =
right thing=20
and separates the frame into its fields for display.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana=20
size=3D2>end-------------------------------end</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DVerdana size=3D2>thanks,</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2>Chris</FONT></DIV></BODY></HTML>

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