[mythtv] DVB-T scan problem with MythTV SVN (r9944)

Stuart Auchterlonie stuarta at squashedfrog.net
Mon May 22 08:45:27 UTC 2006

On Sat, May 20, 2006 at 04:30:45PM +0000, Aidan Thornton wrote:
> > From:: "Aidan Thornton" <makomk at lycos.co.uk>
> > To: mythtv-dev at mythtv.org
> > Subject: [mythtv] DVB-T scan problem with MythTV SVN (r9944)
> > Date: Sat, 20 May 2006 16:06:40 +0000 (GMT)
> > Hi,
> > I tried scanning for DVB-T channels on my HVR-900 (em2880_dvb driver) using
> > MythTV SVN r9944. It found the channels and muxes and added them, however
> > it also added 6 transports with bogus frequencies (2147483647 Hz) and all
> > the channels seem to be associated with them. I'm in the UK, Waltham
> > transmitter, and my (correct) dvbscan-generated channels.conf and a dump of
> > my dtv_multiplex table are attached.
> > I'm not sure how far back this problem goes - I only just started using
> > MythTV SVN. (0.19-fixes doesn't work with this driver - the signal
> > detection code doesn't like it.) Note that I'm almost certainly the first
> > person to use MythTV with the em2880_dvb driver (I had to fix it to get
> > MythTV to work at all), which might complicate things slightly.
> > Could someone have a look at this?
> > Thanks,
> > -- Aidan Thornton
> Oh, and I just spotted the following interesting lines in the output of "mythtv-setup -v siparser,channels" when scanning for channels (I hope LycosMail doesn't mangle this). None of the frequencies listed in relation to the NIT seem to bear any resemblence to either the actual frequencies of DVB-T on the transmitter or the frequencies of the multiplexes/transports added using insert_dtv_multiplex:
> 2006-05-20 17:19:58.348 SIScan(0): NIT: NetID(12297) tranports(6)
> Network descriptors length: 9
>   NetworkNameDescriptor: Waltham
>   Transport # 0 TSID(0x1006) original_network_id(0x233a) desc_len(72)
>   Transport descriptors length: 72
>     Service List Descriptor (0x41) length(18)
>     TerrestrialDeliverySystemDescriptor(stub)
>     FrequencyListDescriptor: frequencies:  61800000
>     Private Data Specifier Descriptor (0x5f) length(4)
>     Possibly a DVB UK Channel List Descriptor (0x83) length(24)

The scanning code has been under heavy development.
There are a number of patches pending submission that
should fix all of these issues. see


if you are interested. The pending patches are at the end of
that ticket.

With reference to the frequency listed above that is an
alternate frequency for that multiplex on the transmitter
you are using. Depending on your physical location that
may or may not be the frequency used. Repeaters generally
use one of the frequencies listed in the other_freq descriptor.


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