[mythtvnz] DVB-T recording artefacts after upgrade to Mythbuntu 11.10 with HVR2200

[Brett]

On Tue, 2011-11-29 at 14:12 +1300, Stephen Worthington wrote:


> The MythTV box I needed to add an aerial amplifier to uses a Nova
> TD-500 card, which is a later version of the Nova T-500.  The tuners
> on Nova T/TD-500 cards are not the most sensitive, but their usual
> problem with reception is caused by the lna (low noise amplifier)
> option not being on.  In recent drivers, it seems to be on by default,
> or automatically controlled, but it used to be common to have to add
> this to /etc/modprobe.d/options-dvb.conf to force it on:
> 
> options dvb_usb_dib0700 force_lna_activation=1
> 

> The fact that you are having reception problems on the Kordia
> multiplex only is likely because it is usually the highest frequency
> and is therefore the hardest to receive.  When I use rabbit's ears on
> my laptop tuner, in Palmerston North, I can almost always receive the
> TVNZ multiplex (lowest frequency), but almost never the Kordia one.
> 
> The force_pid_filter_usage=1 option is new to me, but a little web
> research shows that it will just help in reducing the traffic out of
> the USB tuners to the PC, which helps reduce CPU usage.  It should not
> affect reception problems, unless your CPU is getting overloaded and
> can not cope with the USB traffic and is dropping packets.  Dropped
> packets would cause severe reception problems.  So check your CPU
> usage during recording - it should be very low if everything is
> working correctly.
> 
I thought the HVR2200 would have been a real PCI card.

I have used the force lna option from the start..

The Mt Egmont problem was with a nova-500-td.
But with no internet access, little attempt to fix was feasible.

This reveals the kernel module option status:
cat /sys/module/dvb_usb_dib0700/parameters/force_lna_activation
cat /sys/module/dib3000mc/parameters/buggy_sfn_workaround
etc

USB pid filter option does not solve the problem.

Because reception problem seemed to affect Kordia only (poss frq
selective), I have replaced antenna & cabling (RG6).

The new UHF antenna gives more signal but made no other difference..the
problem looked like corrupted data packets.
This problem only started in last few months.

Thankfully the "buggy single frequency network" option works..