[mythtvnz] Problems with DVB-T

[Stephen Worthington]

On Thu, 4 Feb 2010 11:17:45 +1300, you wrote:

>Hi,
>
>Last week I bought a Nova-500-TD card. I already had a DVB-S card at
>that stage. I had no problems with adding the channels and everything
>worked fine (so it seemed at the time). I scheduled some recordings
>and discovered that it's not as rosy as it initially looked.
>
>Last night I've recorded 'one news' at 6pm. After initial few minutes
>the recording turned unwatchable with serious sound drop-offs and a
>lot of tearing.
>I turned the debug on and that's what I've got:
[snip]

I have not gone through the log output, but the usual problem with bad
DVB-T recordings is that the aerial is not good enough.  Rabbits ears
are only very rarely sufficient.  You need a good external UHF aerial.

Also, with my two Nova TD-500 cards, I found that you should use their
"diversity" feature.  They have two aerial inputs, and they seem to
perform significantly better if you put a splitter in your aerial feed
and plug into both inputs.  In your case, the extra drop in signal
strength from your aerial needed for the splitter might mean that it
is problematic to split it, so you need to fix the aerial first.

>In terms of setup I use gentoo (using overlays, relatively recent
>version of mythtv 23442), video card is a nvidia ge8200 with slim
>vdpau profile.
>I tried to play it using mplayer but it complained in the same places
>(FAAD2). Playing using VLC under windows wasn't much success either.

If a DVB-T file is damaged, there is nothing much that can be done at
the playback stage.  You need to get a virtually perfect recording.
There is some error correcting data in a DVB-T broadcast, but I have
always suspected that they do not really transmit enough redundant
data, as even with a good aerial you can still get an occasional
problem.

One thing I have discovered is that if your recording has a problem,
once the playback has passed the problem point, picture distortion can
last for quite a while - MythTV is not as good at recovery as for
example Mediaportal is under Windows.  It can help to let the program
play for a couple of seconds past the bad point, them jump backwards
(but not as far back as the point where the error was).  After a jump,
Mythfrontend seems to be able to do the recovery it should do
automatically on the fly, and you can get good picture back again (at
least until the next error in the file).

Also, what version of Nvidia drivers are you using?

>What do you think might be the problem here?
>
>kind regards
>Pshem
>
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