Talk:DVB-T

DVB-T2

Would this be a good place to add some basic information that s new study group has been launched to look into the future version of DVB-T called DVB-T2? There really isn't much information at the time to justify a new article. 24.80.38.70 18:31, 26 April 2006 (UTC)

I agree with you. Please feel free to add some info in the article, as you wish. --Cantalamessa 21:41, 26 April 2006 (UTC)

Greed.

It should be emphasized in the article that diital television is being pushed nopt because people will see more beautiful pictures, but rather the government wans to liberate a large chunck of spectrum now used for analog TV and sell it for paying telecomm use or they want to licence 10x many nation-wide TV channels than current analog allows and so collect 10x more licence fees. So it is about money, not the consumer.

What you say can be the truth, but this article merely describes the standard, and does not discuss about politics. Your arguments better fit in Digital terrestrial television. --Cantalamessa 21:53, 6 June 2006 (UTC)

The Times in the UK wrote late last year ( 2007) that the 15 UHF channels was hoped to bring in a one time sum of "well over £ 1 bill." Other comments expect rather less after the 'overpriced' 3G mobile licenses.

£ 1.2 bill. is just £ 20 per capita in the UK - hardly a driving force for any government. So apart from being 100% 'off-topic' it does NOT seems to be a very likely or valid argument. Reslfj (talk) 23:05, 26 March 2008 (UTC)

(maybe this 'greed' section should just be deleted here?

H.264

This article talks about MPEG-2 as the encoding used for DVB-T, however in the UK there are already DVB-T broadcasts using H.264 for HD content. Is MPEG-2 really mandatory to meet the DVB-T specifications, and if not, should references to MPEG-2 be removed from this article? Neilka 09:53, 8 June 2006 (UTC)

Yes, you are right. It would be more correct to write that only MPEG-2 TS is mandatory, whereas the audio and video contents can be different from MPEG-2 (e.g. H.264). --Cantalamessa 15:09, 8 June 2006 (UTC)

Resolution

We should perhaps copy/move this section on resolutions here

Re-write needed?

This article is very technical and doesn't actually seem to tell the casual reader precisely what the heck DVB-T actually is or does. Perhaps a re-write is in order?--Commander Zulu 12:39, 27 February 2007 (UTC)

Actually, DVB-T is a standard, thus it is inherently technical (I've provided only the technical stuff). Some more "commercial" information could be added at the beginning. or we should redirect more precisely towards digital terrestrial television. --Cantalamessa 13:28, 27 February 2007 (UTC)

I agree with Commander Zulu, while this may be a very technical subject, perhaps that the article can start with an explanation on how DVB-T works in a simple understandable manner and doesnt assume that everyone has studied Rocket Science -- Vinylmeister 11:33, 5 June 2007 (UTC)

Flags

Are we going to insert more than one hundred flags in the article? --Cantalamessa 17:14, 14 August 2007 (UTC)

• I agree that it's getting silly ... richi 17:30, 14 August 2007 (UTC)

Who is adding again the flags? Why dont'you discuss that here? --Cantalamessa (talk) 11:15, 8 December 2007 (UTC)

If the flags should stay they should link to info about DVB-T/T2 in the country. I have not added any, but moved Greenland from 'the Americas' to under the Danish flag. I have added a link to Nuuk tv (DTT in the largest city). Reslfj (talk) 15:20, 13 April 2008 (UTC)

Aerials

I think the article is missing a whole section around aerials. We here in NZ are soon to get DVB-T and I had questions around aerials and there are no answers here. Perhaps someone who understands can answer a few basic questions? Are the aerials for DVB-T directional or omnidirectional? If the signal is coming from some location as Analogue TV can you reuse the aerials? If yes is that only for VHF/UHF or both? Imcdnzl 21:33, 19 August 2007 (UTC)

Do you already have a standard TV antennta because they are all on the same VHF/UHF frequency. There is no such thing as a 'digital' TV antenna.--Dacium 02:43, 16 November 2007 (UTC)

Surely this is not true, owing to the requirement to receive all multiplexes, which are spread across the spectrum, whereas existing analogue broadcasts (in the UK at least) were allocated to the high, middle or low parts of the spectrum and aerials sold for each (group A, B etc and W). If you are lucky your existing aerial will work fine, but if you have, say, a low-frequency aerial then you may not receive the high frequency multiplex (often the most difficult) at adequate level, and so some channels will be missing. Wide-band aerials generally have lower gain than those optimised for a particular group of frequencies, so you may need a more elaborate one. Also, if an installation includes distribution amps or masthead preamps these often fail to work on digital because they suffer too much intermodulation from strong adjacent analogue channels (again a big problem in the UK). Good quality preamps with low intermod can result in perfect reception where the aerial alone fails totally, but only if they have the right amount of gain so that no analogue channels clip and hence intermodulate. --Lindosland (talk) 16:19, 28 January 2008 (UTC)

The aerials are not any different for analog and digital signals, but if you want/need to receive both CH21 and CH68/69 you need a wideband aerial or more than one aerial. This holds for analog or digital signals or a combination of both. directional are best as they pickup more signal and less noise, but omnidirectional are often used in boats or mobile homes.

The strict group A, B, E, K, CD or W used in the UK - partly broken until DSO - is not used in some other countries. In Sweden, Denmark, Germany and likely others a transmitter will often use channels with both low and high channel numbers e.g.

Skaane/Hoerby in Sweden uses ch 25,33,41,43 and 61 for 5 MUXes in 5 SFN's. ( http://www.teracom.se/?page=5883 ) (pt. all digital)

Aarhus/Hadsten in Denmark will use ch 26,36,44,55,56 and 69 for the 6 SFN MUXes opening in November 2009. ( http://www.kum.dk/graphics/kum/H%F8ringer/Bekendtg%F8relse%20om%20Radio-%20og%20tv-n%E6vnets%20udbud%20af%20jo/Kanalplan.pdf ) (pt. MUX1 only + 1-2 analog(analogue))

Kiel in Germany uses ch 21,35,39,45,47 and 57 for 6 SFN MUXes. (http://www.dvb-t-nord.de/empfangsgebiete/media/hhshkiflparameter.pdf (Kiel area all digital)

But a group A aerial can be much better than any wideband near the limits of the area covered. Less so for the other groups. Reslfj (talk) 22:51, 26 March 2008 (UTC)

DVB-T2

"It is expected that by 2017 there will enough DVB-T2 equipment to switch all transmissions to DVB-T2 128QAM mode"

The 128QAM mode is speculations. What is known, is that new modulation and new FEC will be used to increase the net bitrate by 'at least 30%' under equivalent conditions. 128QAM will not be in the standard. Reslfj (talk) 21:05, 7 April 2008 (UTC)

The 2017 date may come from a consulting report written for the BBC - called secret Ofcom report. However this report only describes what they think will be possible within the next 10 years, and it is not an Ofcom report

I agree that when 'enough DVB-T2 equipment' is sold, all transmissions will be switched. For some COM-MUXes this may well be (much) earlier than 2017. Ofcom writes - about the 2 PSB MUXes and DVB-T2: 'not in the foreseeable future' and that is not unlikely to be after 2017. —Preceding unsigned comment added by Reslfj (talk • contribs) 11:30, 26 November 2007 (UTC)

Unlikely to be after 2017 may well be much before 2017 in many places. Reslfj (talk) 04:55, 1 March 2008 (UTC) I have removed this date - it was pure speculation.

Can we expect all Freeview transmissions to change to DVB-T eventually, in other words is it compatible so far as existing receivers are concerned (or are they software upgradable)? If it is not, then presumably bandwidth will continue to be wasted long into the future and only new 'HD capable' boxes will receive the improved standard. --Lindosland (talk) 16:09, 28 January 2008 (UTC)

DVB-T2 cannot be received with present DVB-T receivers - DVB-T2 is hardware more than software - there will never be a software/firmware update. DVB-T will not be used in the future, only the timeing is unsure and country dependant. Reslfj (talk) 04:55, 1 March 2008 (UTC)

I have added info based on a RAI presentation in Rome April 2. Reslfj (talk) 21:07, 7 April 2008 (UTC)

Added info about the current status of the DVB-T2 standrad taken from RAI(above). The current text on the DVB.ORG T2 web page is a little 'strange' and sounds somewhat 'politically motivated'. If you quote it, then 'Count your fingers' afterwards.

Added a link to the final Ofcom statement about HD via DTT (using DVB-T2 and MPEG-4). Reslfj (talk) 20:28, 8 April 2008 (UTC)

The Ofcom plan is not a development plan, it is the final decision statement and this should be reflected in text. I have again added the comment about the draft waiting for approval . At this stage everything will be very technical, but a less technical prolog text may be written now . Reslfj (talk) 17:41, 9 April 2008 (UTC)

Hello Reslfj, ok for the Ofcom plan. I have removed the sentence with "currently", since this is not a wikinews article, but a wikipedia one and should be written in an atemporal way. Moreover, the bold emphasized numerical figures look like some sort of POVvity, thus I think it is better to put them on a lower level of attention. --Cantalamessa (talk) 19:28, 9 April 2008 (UTC)

What about moving the section "DVB-T2" in the relevant page DVB-T2? I think we have enough information to do that? --Cantalamessa (talk) 11:12, 10 April 2008 (UTC)

I think making a DVB-T2 page should be done when the standard is published late April - early June AFAIK. The functional blocks should be described - hope for some whitepaper to be published by DVB.ORG at draft publication time. The guard interval 19/128 as listed in the RAI article is listed as 5/32 (=20/128) in other Internet notes. Small diff. I will change it when/if I get more info. Code rates below 1/2 is not in the RAI article, but I have seen it elsewhere. I will change if needed. Need to write about 'Interleaving'. 10 dB better impulse robustness, but not enough info. Reslfj (talk) 15:32, 13 April 2008 (UTC)

Agree. --Cantalamessa (talk) 20:05, 13 April 2008 (UTC)

Revisions to lead

This is somewhat as a follow-up to the similar changes on the OFDM article (see Talk:Orthogonal frequency-division multiplexing#Changes to article lead); here are my thoughts, but I won't act on them right away:

1. "Modern" should be avoided, as its subjective at best, and requires a frame of reference.
2. "method of modulation" - DVB-T describes the entire standard, including the multiplexing, interleaving, FEC coding, energy dispersion and signalling mechanism; it's not just the modulation method (OFDM)!
3. As discussed on the OFDM talk page, I don't think that specific numerical examples are appropriate for an article lead. What's more, "bit length" is a misleading concept; there are no individual bits going out on air, as higher-order modulation schemes are in user (QPSK and QAM).
4. Singling out the SFN ability to this extent is giving it WP:undue weight. It's just one advantage that OFDM brings; other advantages of at least equal importance (if not more so) are the ease of equalisation, timing insensitivity, and the ability to use an FFT to generate and separate the sub-carriers.

Regards, Oli Filth^(talk) 22:22, 28 January 2008 (UTC)

I think that this article needs a clearer intro, but the recent addition is too much offset towards explaining OFDM, which is beyond our scope, here.

1. Maybe Digital could be better than Modern.
2. Agree, DVB-T has little to do with modulation only, it entails everything.
3. Agree again. There are complex symbols or waveforms, on air, not identifiable with information bits.
4. I am for keeping this, though with different terms. After all, SFN is one of the main advantages of DVB-T.

I'll do the changes, if there is consensus. --Cantalamessa (talk) 22:47, 28 January 2008 (UTC)

I agree that SFN should be mentioned, but not to this extent. I absolutely agree that it's one of the key advantages of DVB-T, but from a system design point of view, by no means the only important one. If a single-carrier scheme were used instead of OFDM, for example, equalisation and synchronisation would become much more complex, which in turn would greatly increase the complexity and cost of receivers. There are dozens of important design choices that were made in designing the standard; having this much material on SFN implies it's proportionally more important. Oli Filth^(talk) 23:02, 28 January 2008 (UTC)

One other point; "In simple terms" should be avoided; either the following material is true or it's not. Oli Filth^(talk) 23:06, 28 January 2008 (UTC)

I suggest that no description of something as complex as this is ever quite true! In teaching it helps to start with approximations and then add refinement. Saying "in simple terms", or "roughly speaking" is a way of saying "this is not a strict definition". I took a look at AM broadcasting for comparison. The one-sentence intro there says nothing very useful and I feel it could be much improved! Frequency modulation does open with a comparison with AM and a simple description, as well as mention of common use in radio and TV sound. --Lindosland (talk) 22:12, 31 January 2008 (UTC)

Renaming "DVB-H and DVB-SH" article back to "DVB-H"?

Please add your vote or comment to the discussion regarding the name of the "DVB-H and DVB-SH" article, previously named "DVB-H". See Talk:DVB-H_and_evolution_to_DVB-SH#Moving_back_to_DVB-H. Mange01 (talk) 09:48, 6 February 2008 (UTC)