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Old 07-06-2007, 13:57   #31
digitalradiotec
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Quote:
Originally Posted by simone
Bandwidth should be 9 kHz, if you mean only the audio bitrate, it is 23 kbps, parametric stereo as I already mentioned here:
http://www.drmrx.org/forum/showpost....6&postcount=21
Simone

Thanks very much.
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Old 07-06-2007, 14:09   #32
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Quote:
Originally Posted by simone
Hi digitalradiotec,
after having a look at your website I wonder about your question here, the missing 0.6 kbps would probably not help you!
quote from your website:...they're using a bit rate as ridiculously low as 23 kbps, it is inevitable that the audio quality would be very poor
Although I can not listen live on this transmission, I agree with James (see post from May 23rd) that the mode/ bitrate are a good choice, two of our ARD stations are using the same configuration for audio (not the dataservice) and sound quite good.
Simone

We'll have to agree to disagree then, because I've reviewed the Morphy Richards 27024 for a hi-fi magazine, and I've listened to quite a few other recordings of similarly low bit rate DRM transmissions, and I think the audio quality is terrible - although it's hardly surprising that it is terrible considering how low the bit rate is...

If you read my website you will see that I am very critical of the audio quality on DAB, but I would say that the audio quality of low bit rate DRM stations is significantly worse than on DAB.

The way I look at this situation is that comparisons with AM radio are irrelevant, because this is the 21st century, and IMO, a digital radio system should either provide good audio quality or it shouldn't be used at all (in the developed world, at least).

An obvious solution would be to use 20 kHz channels instead of 9 or 10 kHz, but these 23 kbps streams are a joke, I'm afraid.

Sorry to be blunt, but that's how I feel.
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Old 08-06-2007, 13:51   #33
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Hi digitalradiotec, I read your post with interest and I do have some sympathy for your position.
However my personal experience of listening to the different bitrates of DRM (and I have quite a nice presentation with different audio samples with bitrates going from 4 kbps to 40 kbps, unfortunately far too big in size to e mail) is that there is a dramatic increase in audio quality from going from 4 kbps to 20 kbps but adding extra bits rate after 20 kbps gives diminishing returns in terms of improved audio quality. BTW if you think 23 kbps is "a joke" I wonder what term you can use to describe audio at 4 kbps!?

I have come across certain people in the industry who have a remarkably tuned ear and can hear imperfections that 99 % of people would not notice. I suspect you are in the 1% category. To me in a normal listening environment (home) I don't perceive much difference in the sound quality of a 23kbps AAC DRM bitrate and one of 35 kbps. Once in a car then with the background noise I think the benefit of using higher bitrates is even less. Call me Mr Average but at the end of the day the majority of people will be happy with 23kbps.

It will be interesting to see the results of the trial when they are published in a year or so as there will be a survey of perceived audio quality. I bet the majority of people will be satisfied (or better) with the audio quality.

Having said all of the above, there was a recent test in India using 18 kHz wide RF signal with a bitrate of about 35 kbps which went down very well with the ABU.

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Old 08-06-2007, 14:11   #34
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Smile Sound sample

Talking of sound samples here is an MP3 file (off air recording while I was driving around on 1st May) that has the Radio Devon DJ talking about the Radio Devon DRM trial
radio devon comments on digital trial
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Old 14-06-2007, 12:31   #35
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More audio samples

Here are some more samples of Music that I recorded off air on May 1st that we (Simone & myself) finally got round to extracting from the recorded data file.

here comes the sun (good stereo effects) 1.25MB

every possible way 3.3 MB

Is this quality of audio acceptable or not? Would you listen to this instead of an FM station?

James
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Old 17-06-2007, 20:21   #36
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Quote:
Originally Posted by jbriggs
Here are some more samples of Music that I recorded off air on May 1st that we (Simone & myself) finally got round to extracting from the recorded data file.

here comes the sun (good stereo effects) 1.25MB

every possible way 3.3 MB

Is this quality of audio acceptable or not? Would you listen to this instead of an FM station?

James

It's very good with me. Not perfect but considering what awful MW quality we've had to endure for decades in the UK DRM is like CD quality in comparison, not that it is of course. Come BBC and ILR get your act together we need dozens more stations switching to DRM asap
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Old 17-06-2007, 21:04   #37
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The recordings have been linked from a Chinese radio forum,would be interested to know what they think but unfortunately I am not able to understand any of the comments there
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Old 18-06-2007, 01:20   #38
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Hi,every one. I'am the person who put the link to that Chines radio forum. I just want to raise the public awareness of this new digital mode, and see the reaction.

Generally, they are very satified with its high audio quality.Some of them comment it's even more stable than FM. At the same time, I can see ordinary radio listeners are eager to take up this new technology, unfortunately "Plymouth" is a long way off China and China lies in the shadow of DRM "black hole".
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Old 18-06-2007, 03:50   #39
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Hi zfyoung,
thanks for your reply, looking at the number of downloads refering to the Chinese forum there must be quite an interest in DRM among those listeners.
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Old 18-06-2007, 14:16   #40
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James,
Many thanks for the audio samples from Radio Devon. As a DRM listener from early 2004, I can only receive longer distance stuff at my location, mainly SW + 1440,1593 & 177kHz. I have listened to Orfordness using the DX Tuner system from Sweden & 855kHz seems nearest to that in quality. The DX Tuner thing is now closed, so that's out!
I would be interested to know why Radio Devon's MW was picked for the trial, other than maybe a low audience.
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Old 21-06-2007, 13:46   #41
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Quote:
Originally Posted by jbriggs
Here are some more samples of Music that I recorded off air on May 1st that we (Simone & myself) finally got round to extracting from the recorded data file.

here comes the sun (good stereo effects) 1.25MB

every possible way 3.3 MB

Is this quality of audio acceptable or not? Would you listen to this instead of an FM station?

James

Used standard computer speakers and medium range hi fi speakers, no line in to my portable radios unfortunately.

Interesting examples, first one I found too flat, compressed and with some artefacts, when the percussion comes in it becomes irritating as the higher frequencies aren't there. It's a track I have heard a lot.

Second one, which is a more modern track and with, I think, less instrumental variation on the track, sounds poor at the start (a bit odd, sounds as if the sound level has been set too high briefly) and then is broadly acceptable, apart again from the percussion at times. The SBR, to me, just doesn't seem to work as well as it seems to claim on the Coding Technologies website. Does switching off the parametric stereo improve the audio?

Going back to the speech sample you posted earlier that sounded fine.

Not sure in what context you are asking the last question, i.e. switching off FM or a music station competing with FM, so I'll answer it in my own way.

Broadcasting is becoming multiplatform, including digital, and DRM itself can be used on different bands and with different parameters, particularly when the DRM+ standard gets ratified. The examples illustrated, particularly the first one, are not, to me, an acceptable alternative to an FM music station, given good FM reception with no multipath distortion. But an FM station could migrate to DRM+ anyway and get the same coverage area, they could even start on Band 1 and migrate up to Band 2 at some point if it is decided to work towards analogue switch off.

The second track would be acceptable for listening in the car or at home as background listening, however I would expect that there would be an internet or satellite feed of better quality, given recent advances in internet audio, for more serious listening. The first track needs a higher bitrate. Going back to your previous point, about 23.6 kpbs being used in the tests and not being varied, according to the drm.co.uk website you can use 27.8 or 30.8 kbps with less protection. If AM is going to be used as a single frequency network can't you then use an increased bit rate as the extra transmitter(s) will help in maintaining coverage in fringe areas.

As I understand it the BBC is testing DRM on AM mainly as one possible digital alternative in areas where DAB can't penetrate. I see from a recent report in Media Guardian that they are looking at DRM as well as satellite and wifi in this context.

Why put music stations on medium wave DRM at this bit rate given the alternatives? I would look to be putting mainly speech networks on DRM AM at European 9 khz bandwidths which in itself would free up other digital modes, i.e. DAB, DAB+, DRM+ for music stations. I appreciate Luxembourg sees it as a fill in service for areas of France and Germany where they can't get FM coverage and that DRM is useful for international broadcasters but do national broadcasters need it for music based services?

Of course you need the receivers on the market and we have an increasing number of DAB MP2 receivers in the UK which is a legacy problem for possible DAB+ migration never mind possible future DRM usage.

Last edited by MikeB : 21-06-2007 at 16:49.
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Old 21-06-2007, 16:23   #42
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Seemed to me that they are doing lots of phone conversations on the program, so they would certainly not need the par. stereo and could easily even reduce the bitrate.
In a car or on portable radios the audio quality for me is OK to listen also to music occasionally, but in general I think DRM should be used to replace AM transmissions with mostly speech. Especially on DRM transmissions of international broadcasters it is not the chosen bitrate that is limiting the audio quality, quite often it is the quality from the studio or the audio feed (quality and audio bandwidth).
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Old 25-06-2007, 15:51   #43
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The BBC has given its views on DRM in sections 17 and 18 of its response to the Future of Radio consultation, sections 14, 15 and 16 state that the BBC remains a major user of medium wave, Five Live having a weekly reach of 6 million and it being an important and integral part of local and regional coverage :

17. Given our usage of medium wave, and the potential short-comings of local radio on DAB, we have begun a trial of the only alternative digital radio technology which seems suitable for this waveband: digital radio mondiale (DRM). The trial is re-using the frequency for BBC Radio Devon in Plymouth, converting this to DRM operation, and then researching the reaction to it with a specially selected audience panel. The transmission has been in operation since the end of April 2007 and it is too early to draw any conclusions from the trial. Nevertheless, it demonstrates that DRM on medium wave in the UK from an existing transmitting station is technically possible, even if there are
considerable engineering challenges to be met.

18. For this reason, we consider that it is too early to determine whether DRM has a part to play in the future of radio. Just as it was with the introduction of DAB, the key will be the availability of radios which are able to receive the transmissions. We believe that the next three years will be crucial for DRM, as the intentions of radio manufacturers become better known and the technologies of choice for the future become clearer. In three years, there may well be DRM networks on-air or planned in other countries and the use of DRM for international broadcasting may have brought the receiver market to maturity.
Similarly, over the next three years, DAB+ may have been sufficiently adopted to have become built in as default to receivers (and we note that if it did, its elements of commonality with DRM may make it easier to implement the latter in receivers also). In the same timescale, WiFi radio may be better established and Wimax might have come to fruition. To make a decision now on the choice of technology is too soon.

The full BBC response may be downloaded at:
http://www.ofcom.org.uk/consult/cond...dio/responses/

Sections 12 to 34 give the BBC's views on use of digital technologies.
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Old 27-06-2007, 21:38   #44
jbriggs
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Hi Mike thanks for the posts.
Quote:
Does switching off the parametric stereo improve the audio?
The Parametric stereo does have a small bitrate overhead so I personally would not use it below 22 kbps as I think its better to put all the available bits into the basic mono AAC encoder. Having said that I do see some broadcasts using Parametric stereo with datarates as low as 17 kbps.

BTW here's some information I found on a press release from UBC that mentions the Radio Devon transmissions: Its quite long so I edited it and just left in the stuff about Plymouth. Full press release is on the UBC web site. I think this explains the "missing" 0.6 kbps referred to in an earlier post on this thread!

25 June 2007
.... and BBC use UBC software for Digital Radio Mondiale initiative in the UK

UBC Media Group plc (UBC:L) today announces .... In addition, it announces that the BBC has chosen Unique Interactive to provide Display Text and Electronic Programme Guide (“EPG”) data for their Digital Radio Mondiale (“DRM”) trial in the UK.

...

The EPG Management system collates programme schedule information such as the name of the show, the presenter and additional programme details and sends it for broadcast, for display on DAB, DTTV, DRM, HD Radio and Satellite Radio receivers.

....

The BBC’s DRM initiative is centred in the South West of England, and is set to assess the practicality of digital radio services in the medium wave bands. DRM is an emerging technology that has been designed to facilitate digital radio at frequencies below 30 MHz. The trial commenced in April 2007 and will report in mid 2008. Unique Interactive will be supplying their “ManDLS” Display Text and EPG Management software for the trial.

Simon Cole, Chief executive of UBC commented:

“We are thrilled to see such validation of our investment in software products from major global radio companies. ....... The BBC trial also fits with our belief that digital radio is ubiquitous and platform agnostic and we very much look forward to working with the BBC towards its successful completion of the trial”
...

John Allen, Head of New Services, BBC English Regions, added

“The addition of the EPG on DRM receivers lets users discover our radio programmes as easily as possible adding an extra dimension to the trial that we hope will prove compelling to our listeners. Unique Interactive is leading the field in this area and is already providing EPG services to the UK DAB market."
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Old 28-06-2007, 11:49   #45
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Quote:
Originally Posted by jbriggs

John Allen, Head of New Services, BBC English Regions, added

“The addition of the EPG on DRM receivers lets users discover our radio programmes as easily as possible adding an extra dimension to the trial that we hope will prove compelling to our listeners. Unique Interactive is leading the field in this area and is already providing EPG services to the UK DAB market."

I wonder about that, I thought the listeners on the trial are using the Morphy Richards or Roberts MP40, as far as I know both do not support the EPG.
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