[mythtv-users] venetian blind picture

Greg Woods greg at gregandeva.net
Mon Jul 18 13:42:33 EDT 2005

On Sun, 2005-07-17 at 20:14 -0600, Chad wrote:

> The settings I was referring to are the ones you 'guessed'.  If those
> aren't working, maybe there is something in the backend logs that tell
> why.  Also, you could start the frontend from an xterm to see if it
> provides any feedback on reasons it's not working. 

As far as mythtv is able to tell, it is working. Recordings get made and
stored, they can be seen in the "Manage" section, it's just that the
parameters for the recording are incorrect so what gets saved is
garbage. I don't see any error messages at all in the backend logs or
when running mythtv in a terminal window, but it may be that I just
don't know what to look for.

At the moment, I'm ready to just give up on this. I don't really want
to, given the amount of time and effort I've already put into it, but it
appears to require more technical knowledge about TV signals and video
formats than I have, which leaves me guessing at what boxes should be
checked and what values should be set for things. It also seems unlikely
that anyone else would be able to diagnose my problem for me unless they
had access to my system and could run Utilities/Setup for themselves, so
I think I have hit a dead end. Maybe someday when I have time to learn
all about TV signals and video formats and have some clue what I am
doing, I could try again.

What is *really* frustrating is that it was working at one time.

>  And in the end, if
> it is indeed working, maybe it's not interlacing, and it just reads
> like that is the problem.

I don't know if this helps, but I tried running mplayer with "-vf
scale:-1:1" which is supposed to turn on interlacing. That changes what
the picture looks like, but if anything it's worse. Looks more like
interlacing is already on when recording but needs to not be on. Given
that xawtv works, that seems likely, but again, I lack the knowledge of
TV signal types and video formats to really know, so I'm just guessing

I also don't know if this will help either, but another problem I now
have that I didn't previously have is that I cannot change channels
while watching live TV. It will show me whatever the last channel was
that I had tuned to with xawtv, and it looks fine, but the up and down
arrows have no effect. I wouldn't think this is related except that it's
also a new problem I didn't used to have. I didn't notice it until now
because I haven't been using Myth to watch live TV since xawtv is easier
for me to use for that purpose.

> I get 1 station that gives me something like you are describing, and
> for me, it's from a crap signal. 

In my case I think I can pretty well rule out problems with the card or
the cable signal, because xawtv works and I have tried recording off
several different channels. Also all this USED to work, so it almost has
to be something in the recording settings that is wrong.

It all started when I was having trouble trying to burn DVD's because
my .nuv files were in the wrong format (MPEG-2 vs. MPEG-4), so I started
tweaking settings trying to get things to come out in a different format
and somehow screwed things up. But even a complete rerun of
mythtv-setup, removing all of the settings and starting over from
scratch, has not fixed the problem or caused any other problems, it's
the same old same old no matter what I try. Transcoding works in that it
runs, and the file size shrinks appreciably, but it doesn't correct the
venetian blind picture problem. I don't think I'll try anything more as
long as I am still just guessing.

> If you can, grab a cheapie bt8x capture card (they are like 20 bucks
> online) and see if the problem goes away.  

This is unlikely to help either (except that I might be using a
different driver and therefore different settings). It also doesn't
explain why things USED to work with the card I now have. I shouldn't
have to do this, it feels like throwing good money after bad.

> It's not a great plan, but
> it'll give you second card anyway so you can toy with and use the HDTV
> card for what it was intended ;) 

Not a bad idea in the longer term, but I have to convince myself that I
can even make this setup work at all first. For it to be really useful,
I am going to need a front-end machine in the main TV room, and that is
too much money to lay out until I'm convinced this can work with me at
the controls. I would also need an antenna to get OTA HDTV signals. I
live in Colorado, near the eastern face of the mountains, so reception
really sucks here; ghost signals bouncing off the mountains are a big
problem. An antenna for me is going to mean a high quality rooftop
model, rabbit ears do not work here, so that is a signficant investment
as well. It might be worth it, but more likely, I would have to go to
digital cable to get the HDTV shows I really want (mostly sports). This
again displays my ignorance of how this all works, because what I have
read on this list since I started suggests that the only way I can
really get HDTV from digital cable is to use a firewire link from the
cable box rather than using a capture card at all.

>  And it will also give you the
> ability to rule things out, like channel signal problems (assuming
> it's also a local broadcast channel).

All I have right now is analog cable. I have tried recording from
several different channels and they all have the same problem, but the
ultimate source of the content probably doesn't matter that much, the
delivery method is analog cable in all cases.

> You noted xawtv works fine, and said you may have dorked something up
> in the recording profiles.  I'd play around with those settings,
> switch between RTJpeg and Mpeg-4 and adjust the quality settings

I think the solution lies here somewhere, but I spent a whole day
Saturday doing just this without success, so my frustration quotient is
exceeded for now. Unless I have something better to do than guess, it
will probably be a while before I come back to this.

> A re-install probably won't help, but maybe a backup and re-do of the
> database might. 

I have already tried rerunning mythfilldatabase after re-running
mythtvsetup and saying "yes" to remove settings when asked, but I think
you mean something more than that. 

>  It may be a bit time intensive to import back in your
> existing recordings after you get the database reconfigured

I don't have too many of them right now, so if I knew HOW to re-import
something, I could probably handle this.


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