Linux DVB and digital switchover in the UK

[The Natural Philosopher]

For those of you who run TV cards on Linux in the UK..and are having trouble retuning using 'scan' because the transmitter files that come with the standard distros of dvb utilities don't work any more, here is the way to sort out how to patch them

First of all you need to find the transmitter definition files.

Mine were in /usr/share/dvb/dvb-t

Copy the one you use into somewhere else - home directory Go to this website

important thing is to declare yourself trade, and the postcode is obvious from the above URL (this one is in Surrey)

That nets you your local transmitter data.

To convert channel number to frequency, as the transmitter files require, take the channel number and add 38.25 to it, and multiply by 8. That's the frequency in MHz.

If there is a plus after the channel number add 0.167 MHZ.

E.g. channel 50+ is 88.25 * 8= 706MHz plus 0.167MHZ = 706167000 HZ.

That's the second parameter of the new entry.

The third is always 8Mhz, the channel bandwidth.

The fourth sixth and seventh are modulation types. If you hover the mouse cursor over the channel number on that page, they are revealed . I.e

64QAM 2/3 8k DVB-T

These go in the fields in the new entry in the transmitter file so e.g.

T 706167000 8MHz 2/3 NONE QAM64 8k 1/32 NONE

is a valid entry

I have no idea what the 5th, 8th and 9th parameters are I left those as NONE, 1/32, and NONE

My modified uk-sudbury file is this

# UK, Sudbury # T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy # 49+ MUX A SDN T 698167000 8MHz 2/3 NONE QAM64 2k 1/32 NONE #41 MUX2 d3 &4 T 634000000 8MHz 2/3 NONE QAM64 8k 1/32 NONE #44 MUX-1 BBCA T 658000000 8MHz 2/3 NONE QAM64 8k 1/32 NONE #47 (HD) T 682000000 8MHz 2/3 NONE QAM256 32k 1/32 NONE #54 Arqiva A T 738000000 8MHz 2/3 NONE QAM64 8k 1/32 NONE #50+ Arqiva B T 706167000 8MHz 2/3 NONE QAM64 8k 1/32 NONE

Hope this helps anyone else struggling to retune - several times - in the mass switchover being undertaken this year.

Note. Scan didn't understand the HD MUX. Which is OK because neither does my Hauppage dongle :-)

Note this is all Linux specific. Most other TV software has better self scanning than Linux :-)

[Mark Williams]

Or use `w_scan' (), thus avoiding the need for the initial tuning files?

[The Natural Philosopher]

If I read German, I might...

[Dave N]

Unfortunately you seem to have missed the link to English text, shown in large letters at the top of the quoted URL page. The download link and changelog are only available on the German page as is explained by the English text, however, but they are obvious.

The given examples make this utility seem potentially very helpful, but requires compilation from source code. I haven't used it myself so I cannot comment on its effectiveness.

[Dave N]

Dave N wrote, on 02/08/2011 07:18:

There is a guide (English on Ubuntu) to w_scan here:-

Apparently I was wrong and the tarball includes a precompiled binary. There is a comparison of scanning utilities on LinuxTV Wiki:-

[The Natural Philosopher]

downloaded and compiled OK..seems to be a pretty good tool...running a scan now..

Hmm. Nope. Its all over the feckin place. Half the channels are missing and the rest are on frequencies I dont recognise.

Doesn't seem to cope with the offset channels at all.

[The Natural Philosopher]

As I said, it doesn't seem to be able to cope with the current mess that represents all the offset channels.

To be frank,. neither did the wife's MAC OSX software (eye-TV) had to manually tune that to the offset frequencies..and a weird bug has turned up in the STB's as well. radio stations cut out after a few seconds.. and the screen displays channel info but no sound. Had to set it in 'menu' mode to listen to Test match special. That stops it doing that..

Sigh. I guess the software will catch up, eventually.

[Dave N]

Pity but, as you say, the software will eventually catch-up I hope. Is it a peculiarity of the UK adopted system causing these complications?

[The Natural Philosopher]

I think the Great Digital Switchover is proving to be the Great Digital Cockup actually.

These offset channels are simply abominations if you aren't expecting them..and it seems taht even when you are thins dot go right.

scan got two sets of answers, one for the channel, one for the offset channel, at first. I deleted the wrong duplicates..

Eye-TV got two sets, and deleted the wrong set, and needed to be manually rescanned on the exact frequency. Or it said 'no signal'

the SONY STB works, except as noted the radio stations stop working after a few seconds. Not sure why, except the presence of video info seems to confuse it..sigh..

It seems to be a combination of 'whatever works today, use it'

[tony sayer]

Well with the number of channels that have to be shunted around its done quite well really. The alternative is to make everyone go satellite or shut the terrestrial network down for a few weeks but can you just imagine the riots if the nation were deprived of Corrie for a few episodes and what ever might happen to the birth-rate;?...

They have as line-offsets been around for a very many years. If the software can't cope then blame the designer/writer!...

Duff s/w package perhaps?. We've got a few PCI type satellite receivers here and the odd software update is quite welcome sometimes ..

[Mark Williams]

So you claim. But having just checked our transmitter with the URL given in the OP, all of the [pre-shuffle] DVB-T multiplexes (except the HD one, which my card cannot demodulate) are listed as either `+' or `-' offset channels. `w_scan' Just Found Them in December 2010 and August

2011 at the expected frequencies. I hadn't even noticed that the multiplexes weren't exact multiples of 8MHz apart until this thread.

OTOH, we seem to have reasonable reception here and TPTB haven't started switching the analogue signals off, shuffling the channel allocations around or broadcasting the DVB-T at higher power yet. If you have marginal reception and/ or hardware, then it might be worth trying expert options such as the `-F' and `-t 3' timeout options.

[The Natural Philosopher]

I have no reason to lie.

But having just checked our transmitter with the URL

TBH now I understand what's a-going on, its no big deal to and edit the locale file.

I spent a morning with w_scan, and a simple scan did not get all the channels and some of what it did were not on the right frequency. They might have been Sandy Heath sidelobes..that comes in quite well here..borderline between that and sudbury, though I point at sudbury.

Anyway haveing been up half the night trying to make wifes Macintosh work..would you believe that a program - Quark Xpress - installed and never generated a directory for its preferences, and , failing to find it, crashed with a segfault?

In the documentation it tells you how to make it. (Should you have problems)

Not only was that present as a fault on the original installing script, but also the three upgrades subsequently applied over it. Ye gods. This is code that sells for the best part of a grand..though we got this second hand for a lot less.

All for the sake of an

If Not exist PREFS DIR THEN create PREFS DIR.

Christ its so basic, and then when you fail to open the preferences files, no check there either, assume its open, uncorrupted and you have the data.. and if you don't? Well, sod it. Segfault.

That bug there for 2.5 years at least. In fact judging by what I found on line, its there for 5-6 years further on... I get better stability on Linux free code than that.

[Mark Williams]

The evidence you posted does not necessarily support your claim, that's all. My evidence directly contradicts your claim.

You can probably get some indications about which transmitter `w_scan' finds with a `-v' option (or two). You should definitely be able to tell from the frequencies, though. If it is finding and preferring transmitters which you didn't expect, then it might indicate reception problems. Can you find out what power level, signal:noise ratio and decoder error rate you are getting from the `right' and `wrong' frequencies?

Yes, that is very easy to believe of proprietary software. Serves you right for being in that position, IMO (cf. the `poverty' thread).

Is that supposed to be parsed as `Linux-free code' or `Linux free[dom]-code' :-)?

[senoir.dude]

Sir. Thank you so much for taking the time to post clear instructions!

I've spent hours wrestling with a transmitter update in April 2018 due to MythTV and its channel scanner not picking the strongest signal channel, only the first transport it comes across.

Unfortunately it was getting signals from two transmitters, one very weak but first in line so to speak. So 50% of channels were missing. And the DVB-T Linux Apps files are out of date.

Your post has everything working again :)

Thank you!

[Brian Gaff]

And its been know since 2011 as well. Hardly the best advert for Linux I've seen. Brian

[dennis]

The best advert for open source software built on linux are the embeded devices like routers, nas boxes, etc. where the user doesn't know or need to know its linux based.

The worst are where its trying to be a desktop OS.

[John Rumm]

... and part of someone's botnet due to lame security and no updates ;-)

[dennis]

Fortunately they are still updating my router and my NAS boxen. Some may not be so lucky.

[The Natural Philosopher]

Oh dear. Anyway kaffeine which I use doesn't need these files.

A lot has changed since 2011.

[Andy Burns]

w_scan is a good replacement for all the dvbscan/scandvb/tzap/szap utilities and doesn't need an initial tuning file.

I now use tvheadend instead of mythbackend and kodi instead of mythfrontend, and that has very good automatic scanning.