[pvrusb2] HVR-1950 - bad video quality

[Mike Isely]

On Thu, 2 Apr 2009, stan schultz wrote:

> So I got the camcorder out, plugged it into the composit input and the
> picture from it looks great.  As you said, that points at the tuner.  A
> couple searches showed there is all kinds of discussion about bad uscable
> table entries in mythtv. But I couldn't find anything truely useful.  I
> tried modifying the values in /sys/class/pvrusb2/*/ctl_frequency/cur_value,
> but didn't really see a positive difference ever.
> 
> Any Ideas?

Well I only do over-the-air here, no cable, so I don't have a good basis 
for comparison with your situation.  So I don't know how good / bad 
MythTV is going to be when tuning cable.  Obviously the pvrusb2 driver & 
hardware is not going to "care" where the signal is coming from so long 
as the signal is coded following the standard it is configured for and 
that it knows the right center frequency to tune for it.

In your shoes I might consider trying something that can instead 
directly scan all the possible frequencies itself.  I think a long time 
ago I did this once with xawtv - the scantv part of the app IIRC can be 
told to creep through the frequency spectrum with very small increments, 
much higher granualarity than what would normally be required.  This 
might allow you to have a fighting chance at least to figure out the 
right frequencies.

If the issue is not so much the correct frequency table but just finding 
the right channels in the table, then you should try an app that can 
simply do a scan.  Again, xawtv can do this.  (And so can MythTV.)  If 
you try xawtv, please be aware of its caveats - the largest of which is 
that I don't think it's in active development anymore.  The pvrusb2 
driver's usage web page has additional important details about setting 
up and using xawtv:

http://www.isely.net/pvrusb2/usage.html#V4L

Obviously you still want to use MythTV, but if you can get another app 
to tune the hardware properly then you can at least rest assured that 
the hardware and the driver are correct - then you can focus your 
attention on getting MythTV to behave correctly.

Here's another wild idea:

http://home.arcor.de/saedelaere/index_eng.html

I'm not sure if Christian (the author) is going to suddenly want a huge 
pile of attention, but he's been talking to me about this app he's been 
writing.  It's called "TV-Viewer".  Essentially it's a nice looking gui 
that builds a TV app out of other building blocks.  I tried his 0.8b1 
version a few days ago and it looks very slick.  I only mention it here 
because it's capable of doing a channel scan.  You might want to give it 
a spin...

  -Mike


-- 

Mike Isely
isely @ pobox (dot) com
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