[mythtv] problem with HDTV in Australia

[Keith Irwin]

Okay, what you're describing amounts to this:

During recording, the stream is being corrupted.

I'm assuming that the same errors occur each time you watch a given  
video.

Although you say that it's only the video and that the audio is fine,  
I doubt that.  Audio is a much smaller portion of the stream, so if  
errors were evenly distributed, audio errors would show up much less  
frequently, but would show up.  Also small audio errors are more  
likely to be successfully compensated for.

There are two possibilities:
1) There is signal interference at some point before the demodulator.
2) There is an error getting it between the card and the hard drive.

If the second is the case, it should perhaps happen more or less  
depending on what else is happening on your system.  That is, if you  
run other applications which use the hard drive or the system bus a  
lot at the same time, you should see more errors.  If this is the  
problem, you'll have to poke your low level drivers in various ways,  
and possibly get a new motherboard.

I would guess that the first case is more likely.  The computer is an  
electrically noisy place and the places where we keep computers are  
often also electrically noisy as well.  There are a lot of different  
possible sources of interference.  Such as other electronic devices  
and computer subsystems.  You may have a particularly noisy processor  
or motherboard or power supply or even hard drive.  Or other devices  
such as monitors, stereo equipment, and even UPS's may be causing  
problems.  Each of these sources would need to be addressed  
individually.  Because of the level of error correction in digital TV  
transmission, the interference is likely to be correlated with some  
fairly sharp spike of some sort, and not just low level emissions  
from any source.

I found that I tended to get sudden interference when the processor  
went back and forth from being idle to being loaded.  I solved this  
by leaving a heavily niced process running at all times to eat the  
spare processor cycles.  Since doing this, I very rarely get any  
interference.  This solution may not work for you at all, but since  
it worked for me, I figured that I would mention it.

Keith Irwin