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

[Stephen Worthington]

On Tue, 29 Nov 2011 10:02:16 +1300, you wrote:

>Not the same h/w or symptoms but..
>
>Using Nova-500-t & 10.04.3 with recent kernel changes in last month has
>caused terrible break up on dvb-t Waiatarua Kordia only.
>
>Same h/w has worked fine >3 yrs.
>
>Been forced to add:
># pid filter to reduce USB traffic
>options dvb_usb force_pid_filter_usage=1
>(any USB based tuner)
>
>Trying this as well:
># jittery reception nova-t-500 Aust 7MHz & Denmark ?
>options dib3000mc buggy_sfn_workaround=1
>options dib7000p buggy_sfn_workaround=1
>(nova-500-t specific)
>
>I had a possibly similar problem with all 3 multiplexes from Mt Egmont
>couple months back..(nova-500-t ubuntu 11.04) ..system was completely
>unusable as recorder.
>
>Is the HVR2200 based on USB connected tuners on PCI card ?

No, the HVR2200 is a proper PCIe card with dual DVT-T/analogue tuners.

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

I do not have that option set, running 11.04 on that box.  With 10.04,
I think it might well be necessary.

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.