[mythtv] Ticket #1049: DVBSignalMonitor needs to be able to monitor NIT/SDT

[Daniel Kristjansson]

On Thu, 2006-06-08 at 21:57 +0400, Manu Abraham wrote:
> Are you saying that you loose a FE_LOCK due to LNB LO drift ?
> 
> AFAIK, swzigzag is used only once for acquiring a LOCK, once acquisition 
> is complete, it does the tracking by itself. Newer devices, don't do 
> swzigzag too..

The swzigzag problem was encountered by Yeasah. As he described it
swzigzag kicks in before the rotor has finished pointing the dish
and gets hopelessly lost. We were pondering disabling swzigzag,
but the worry was that if we did LNB drift would mean that we
would need to re-implement swzigzag. My belief was that LNB drift
would be small enough that the PLL could adjust for it. Allan's
data backs this up, but Yeasah pointed out an LNB that has a 
+/- 3 Mhz temperature drift according to the data sheet.

Fixed LNB frequency error should not be a problem since MythTV
saves the tuned frequency during the scan for drivers/hardware
that support it.

A further thing to add is that Yeasah found out that his device
supports hardware zigzag and he has some patches to the driver
that will avoid the problematic swzigzag altogether. But other
devices which do use swzigzag could still be a problem.

-- Daniel