Talk:Digital audio broadcasting/Archive 2
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This unique device did not have a screen, but did have LEDs behind a cover that changed colour depending on the device status. It is likely to be most available on eBay.— Preceding unsigned comment added by 22.214.171.124 (talk • contribs) 22:05:48, 29 September 2005 (UTC)
- That's because it wasn't a radio per se, it was just a receiver that plugged into your PC. 126.96.36.199 (talk) 17:54, 19 February 2012 (UTC)
it sure says something about the intelligence of the usa when someone can do a write-up on satellite radio 3.5 years ago and no one has touched it since.— Preceding unsigned comment added by 188.8.131.52 (talk • contribs) 14:03, 24 Dec 2005 (UTC)
- It says maybe more about how many people give a stuff about the subject? 184.108.40.206 (talk) 17:55, 19 February 2012 (UTC)
DAB is one digital radio standard, and IBOC/ISDB/DRM/Satellite are other, different standards - why does this page about DAB talk at length about other standards, particularly IBOC and satellite, and the USA which has chosen not to adopt the DAB standard? Are these issues not covered sufficiently in the 'Digital Radio' entry, and wholly irrelevant to this page?— Preceding unsigned comment added by 220.127.116.11 (talk • contribs) 08:09, 11 Jan 2006 (UTC)
Yeah, Somebody should fix this... and there should be definetly be clearer difference between "DAB"-standard and Digital audio broadcasting in general.— Preceding unsigned comment added by 18.104.22.168 (talk • contribs) 10:44, 15 Jan 2006 (UTC)
- Is it because "DAB" is a particular standard of Digital Radio, a term that sort of implies audio broadcasting in most cases? Perhaps you want to make a disambiguation page if you're that bothered :p 22.214.171.124 (talk) 17:56, 19 February 2012 (UTC)
The section on Single Frequency Networks suggests that broadcasters have to pay particular attention to timing if they use several different transmitters. This must surely depend on how they transmit the data streams to the different transmitting stations. If they use asynchronous digital data transmission between sites, then delays could become problematic, but if they use analogue transmission, then the delays should be more or less insignificant, as the OFDM coding used in DAB should tolerate some variation in timing between different transmitters, and delays based mainly on propagation delays between transmitting stations should be more or less insignificant. If they use digital packet switching for inter station feeds, then store and forward delays, and queuing delays may be very significant, and then there would be a need for some clever techniques to synchronise the different transmitters.
I was going to suggest that the article is wrong, but it may not be. It'd be good to have more information about this. Are there any reputable articles which can be referenced/cited? David Martland (talk) 22:29, 4 April 2010 (UTC)
- The article is correct. In a SFN network you must pay close attention to the transmission delays to different transmitter sites and in order to synchronize the transmission a timestamp is used that tells the transmitting equipment when the DAB frame should be broadcast. This timestamp is relative to PPS (Pulse Per Second) and this implies that the maximum network propagation delay from the multiplexer to the transmitter must not exceed 1 second in SFN networks. Normally telecommunication links such as G.703 or G.704 are used for transmission but IP links are beginning to be of intrest. While propagation delay over 6.70x links are small and easy to calculate) delays over packet switching networks are not. There is an IP based protocol called EDI that has been designed for this. There the relative timestamp is extended into an absolute timestamp. This allows for proper SFN operation even when the propagation delay exceeds 1 second. I'm sorry I don't have any articles or so to link to or so. Kydyl (talk) 15:59, 11 June 2010 (UTC)
Stat out of date
The opening section states "As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format".
I would suggest this stat is irrelevant now - although it would be interesting to know. Has anyone got an up to dtae figure? —Preceding unsigned comment added by 126.96.36.199 (talk) 18:22, 18 September 2010 (UTC)
DAB and pirate radio
The section about pirate radio is becoming less relevant as open source implementations of DAB/DAB+ transmitters are becoming available. There is still a need for specialized hardware to get a signal out but I would guess the first (London) DAB-using pirate isn't too far away (in my not so humble opinion).
DAB+ Bit Rates
I am not sure what it is like throughout the rest of the world but here in Australia, the bit rates for DAB+ radio are appalling, toppign 80kbit/s at most. While this article claims that AAC triples the efficiency of MPEG encoding, my experience is that the sound quality is still pretty poor at 64bit/s, even 80kbit/s, with MP3 encoding at 128kbit/s or more delivering superior sound quality.
Therefore is there is no objection I will add a section to this article under the bit on MPEG bit rates to cover AAC bit rates also, and highlight that to achieve sound quality better than FM then 128kbit/s is still required, with few stations offering this. — Preceding unsigned comment added by Supremedalek (talk • contribs) 02:11, 3 January 2011 (UTC)
- 80kbit/s is actually very high for DAB+ since the system is designed to operate using low bitrates thanks to the HE-AAC v2. Actually I am suprised that more radiostations doesn't use bitrates in the 32-48 region. Remember, this is radio. If you wan't to listen to music on your expensive HIFI equiptment, use a CD. When bitrates are up in the 80+ region you don't use the HE part(SBR) or the v2 part(Parametric stere). So just core AAC is used in your example. Kydyl (talk) 14:16, 14 January 2011 (UTC)
- I have made extensive personal use of HE-AAC in converting audio files for listening on my phone... I default to 40kbit but often find that gives unacceptable results on a good number of tracks and have to upgrade it, sometimes as high as 80k. In all cases there's a noticable quality drop from the high quality VBR MP3 sources, it's just a matter of how critical it is to the material in question. I'm not sure if I'd accept anything less than 96k for broadcast purposes, as the need for realtime encoding (lowering encoder efficiency) and the great range of material under consideration would cause a loss of transparency in too many cases.
- If the new broadcast standard doesn't provide at least as good a result as FM, and more preferably an improvement, then it doesn't count as progress in my eyes - should it? The local FM band already provides a good spread of programming across various genres, both national (BBC) and independent, including some rival indies that are pretty much carbon copies of each other with different names. You can already fit in a great many more stations at 128~192k, enough that many of them get a very sparing market share and disappear soon after launch because they can't get sufficient listener numbers to attract a break-even advertising payout. MP2 DAB has proven this already. Is there really a need to squash even more of them in at 80k, 64k or less? It smacks of greed more than an improvement of the public service. An advance for the sake of advancing.
- I recently bought my first DAB radio as it was in a clearance sale at a much reduced price. I only want it for 2 or 3 digital-only BBC & independent stations. I'm definitely under no illusions that I'm going to get better quality out of it for the also-on-FM stations than the old FM/AM set that lives in the bathroom... Partly because it doesn't strike me as a very high quality radio on the whole, but also because of the signal. 188.8.131.52 (talk) 17:53, 19 February 2012 (UTC)
- well, the fact that you are re-encoding MP3's will have a very negative effect on the audio. Then the AAC codec won't be able to analyse the audio material properly since it will be disturbed by the fact that a lot of the original content is removed and replaced with artefacts. One basic rule in audio and vide encoding is to never use one lossy encoding as the base for another lossy encoding. That will produce crap as you have discovered (even if the source "sounds" fine). Kydyl (talk) 10:45, 11 September 2012 (UTC)
Aerial or Antenna
I came to this page looking for information about DAB aerials and why they are different from FM / VHF aerials. It seems odd to me to have a lot written about reception, but nothing about what you would use to receive. I understand that aerial length and the orientation of signal modulation is important. I don't understand why a telescopic FM aerial can't simply be used vertically and to the required length. Or maybe it can. From lots of Googling, I believe that a lot of people are put off car DAB by the use of substandard in-car aerials, blaming the DAB transmission rather than the aerial, so clearing up this point in this article could be useful to a lot of people. — Preceding unsigned comment added by 184.108.40.206 (talk) 16:28, 24 January 2013 (UTC)
Dab has a shorter wavelength than vhf signals between 88-108mhz cutting a dipole would help boost you reception for dab. — Preceding unsigned comment added by 220.127.116.11 (talk) 00:40, 14 May 2013 (UTC)
Denmark switching to DAB+
Denmark is going to be moving to DAB+ in 2014. All channels are going to be broadcasting in DAB+ by 1-December-2014.
Sources in Danish.
http://www.radioassistant.com/dk/2013/09/digital-radio-danmark-skifter-til-dab-i-2014/ http://www.kulturstyrelsen.dk/fileadmin/user_upload/dokumenter/KS/medier/radio/Digital_radio/Digiradioplan-2013-2019.pdf (this is the long term FM - DAB+ plan for Denmark)