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Listening to the Proms in Extra High Quality

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Rupert Brun Rupert Brun | 16:55 UK time, Friday, 3 September 2010

Illustration for PromsXHQ, BBC Radio 3's high quality audio experiment

Editor's note: for the final week of The BBC Proms you'll be able to listen to the live radio broadcasts from The Royal Albert Hall in Extra High Quality audio. The man who came up with the idea explains the thinking behind the experiment- SB

You could make a strong case to say that of all the digital platforms used by BBC Radio, the internet delivers the best quality. We have invested over the last two years in a completely new system to code our audio for the internet using respectable bit rates and AAC coding technology. The system is known as 'Coyopa', named after one of the two Mayan gods responsible for thunderstorms. The god Yaluk makes all the lightning flashes, Coyopa makes the impressive noises.

Using our Coyopa system we distribute within the UK most of our national radio stations at 128Kb/s whilst Radio 3 is available at 192Kb/s. The audio feed for the internet distribution is derived from the signal path used to feed digital television and in the case of Radio 3 this means (like DAB) that there is no multi-band transmission processing involved. I wondered how good we could make Radio 3 sound on the internet and what people would think of it. Would it be a welcome improvement? Or given that most people don't have high quality amplifiers and speakers connected to their computers, would they even notice the difference?

The bust of Henry Wood - founder of the BBC Proms - in the lobby of the building named after him in Central London

The choice of content for the experiment was obvious to me - we had to use the BBC Proms concerts. They always attract a strong audience and this year we have a brand new outside broadcast vehicle at the Royal Albert Hall and a new link from there back to Broadcasting House. The link from the truck to Broadcasting House is linear (uncompressed) audio with a frequency response extending to 22KHz, making it one of the best audio sources available to us. The signal passes through our internal digital routing systems to the Radio 3 Continuity Suite, from where it feeds our Coyopa internet coder. After the Last Night of the Proms on 11th September the experiment will end, so listen to the stream whilst the Proms are being broadcast and please do complete the feedback form to tell us what you think of the experiment.

By happy coincidence, the experiment has been dreamt up and realised by a team of BBC staff who work in an office building called 'Henry Wood House', named after the founder of the Proms Concerts. Henry Wood House was built on the site of the Queen's Hall, which was the home of the Proms until it was destroyed by an incendiary bomb in 1941. The team walk past a bust of Sir Henry Wood as they come to work each day.

Rupert Brun is Head of Technology for BBC Audio and Music

  • Listen to Radio 3's Extra High Quality Proms audio on the Radio 3 web site during live broadcasts of The Proms until 11 September 2010. On the same page you'll find a link to a survey about the experiment. Please take a minute to complete it once you've tried the Extra High Quality experience.
  • Help us spread the word about Extra Quality Audio for the Proms by tweeting about the experiment using the hashtag #PromsXHQ.
  • Read Rupert's FAQ for answers to the big questions about PromsXHQ.
  • Read this blog post by Radio 3 Interactive Editor Gabriel Gilson on the Radio 3 blog for some additional context.
  • The picture shows audio engineer Brian Hodgson tuning audio generators at the BBC Radiophonic workshop in the 1969. It's from the BBC's picture library. Rupert worked with Brian at the Workshop.

Comments

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  • 1. At 6:31pm on 03 Sep 2010, Neil wrote:

    http://www.bbc.co.uk/iplayer/episode/p009k2dc/Tony_Blackburn_29_08_2010/

    Annoys me this news immensely when you can only provide 80k mp3 that sounds shocking on my amp

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  • 2. At 9:33pm on 03 Sep 2010, John Prince wrote:

    O.M.G. - O!. M! G!.

    I've just been to Albert Hall - and didn't leave my dinner table.

    The Mahler was just wonderful BUT - I was there!

    XHQ - RULES........

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  • 3. At 9:36pm on 03 Sep 2010, dukeofearl wrote:

    Excellent.....

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  • 4. At 9:59pm on 03 Sep 2010, violadamore2 wrote:

    I was listening on headphones here in the USA on a wonderful sunny afternoon in my garden. Towards the end of the Mahler 4th movement, it sounded as if one of the player's instruments malfunctioned and made a loud pop, a string or fiddle bridge I think. The realism of the noise was very surprising. The real music was even better.

    I hope this COYOPA experiment is successful and that you keep it.
    I love the BBC 3 website and all that it offers in the way of classical music.

    The USA is a dessert by comparison.

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  • 5. At 10:06pm on 03 Sep 2010, jaybicks wrote:

    Just listened to the Berlin Phil at the proms. Fantastic performance by the orchestra and what a fantastic performance by XHQ. None of the broken glass effect of DAB and none of the compression we hear on FM. I was waiting for the limiters to come on during the fff passages, but no, just wonderful dynamic range. I hope the dear old Beeb realise that they now have no option but to make the service permanent

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  • 6. At 00:08am on 04 Sep 2010, beckmesser wrote:

    Just recorded and listened to the Mahler tonight (I'm based in London). An absolute delight. Let's not fool ourselves, the coding towards the consumer is one thing, the quality of the whole b/cast chain is another. Hence, congratulations to BBC and Radio 3! Natural dynamic sound of warmth and clarity, agree with jaybicks. No compression in the lower range, maybe slight limiter in some peaks (waveform looks a bit "cut"), but acoustically fine.

    BBC, PLEASE LET US HAVE ALL RADIO 3 PROGRAMS in this 320k format, they deserve it!

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  • 7. At 02:19am on 04 Sep 2010, JLW wrote:

    Radio 3 - 320 kbps AAC - WONDERFUL! 192 isn't bad, very listenable, but at 320 all the power and the glory of the orchestra is there. Would it really be so difficult to carry on at 320 after the Proms finish? Even just for Orchestral recordings from Edinburgh, or BBC SO from the Barbican etc.? One important point - if you can do 320 during the autumn/winter concert season you should flag it up well, not just on the website but in Radio Times too. Go ahead, do it and be proud of it! There are very few Euro Classical stations at 320 mp3, let alone mp4 - (the Berlin Phil Digital Concert Hall is one) so the BBC would once again be in the technical vanguard. I'm not alone in having abandoned FM a few years ago because of the dynamic compression. What joy it has been to return with the iPlayer stream. At 320 you're bound to draw more and more listeners in, just do it!
    Jayne Lee Wilson,Liverpool UK

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  • 8. At 11:28am on 04 Sep 2010, Tam Pollard wrote:

    This is a wonderful development and one I have been waiting for. I'm not sure people mainly listen through laptops - a while back I ditched DAB and moved exclusively to streaming for R3. Fed through my hifi this stream sounds absolutely superb. Given that we get HD content for TV, it seems odd that we're limited to 192 for radio (and bizarrely lower 128 for listen again). Please role 320 out permanently and also for listen again on the iplayer - an excellent way to spend the licence fee!

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  • 9. At 1:06pm on 04 Sep 2010, HD1080 wrote:

    Will you be doing a similar experiment with video - like doubling the frame rate?

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  • 10. At 4:01pm on 04 Sep 2010, lhvandelden wrote:

    Briefly: the music sounds wonderfully clear and natural. I use a laptop linked up with a fairly simple (amplifier) sound system. Please continue this experiment after 9/11. Don't let the date bother you. Thank you.

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  • 11. At 4:12pm on 04 Sep 2010, frances_iom wrote:

    Is there an alternative (on Linux) to using the adobe software which is notorious for both the holes it leaves in any security (especially in any any Windoze environment) as well as allowing all the privacy violating tracking software exploited by the less scupulous companies (eg flash cookies).

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  • 12. At 5:59pm on 04 Sep 2010, happyvalley wrote:

    At last ! Real dynamic range. Whilst bemoaning the dynamic limitations of the medium,I had pretty much accepted that FM was probably as good as it was going to get, and not for much longer either.
    However, those timpani at the close of the first movement of the Mahler really made me sit up. The whole symphony was a joy, and the RAH acoustic was palpable. I only intended to sample the stream for a few minutes but I couldn't tear myself away.
    Please, please find a way to give us more of this quality on Radio 3.

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  • 13. At 9:59pm on 04 Sep 2010, BrianW wrote:

    Magnificent! Saw the BPO last night at the Albert Hall, and tonight I get to hear them almost as clearly at home.

    I've always been impressed by the quality of the live sound the BBC manages to get at the Proms - they obviously know something about recording that most CD producers don't. But digital compression has been irritating - more so on Listen Again than live I think.

    Your new XHQ sound is a significant improvement. Thank You.

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  • 14. At 07:01am on 05 Sep 2010, johnlondonw14 wrote:

    Success and welcome. Hope you can keep the 320kbs feed going full-time.

    Great to hear in finer detail: particularly noticable on the quieter passages. It seemed in the Bruckner there was a more consistent balance overall with less change in audio perspective between quiet and loud passages.

    The reverb from the hall seemd very lifelike though did not come "out of the speakers" as much as I would like - the reverb actually in the hall is very characteristic of the Albert Hall. On the radio on Saturday the reverb stayed narrow.

    Having attended a few Prom concerts this year, the experience from Radio 3 is very much "the best seat in the house" even to the extent that it is impossibly clear and wide sound that is not available anywhere, front arena, stalls, Grand Tier etc.

    What one still misses on the radio is the thrill of the performance and the tension between the orchestra, arena and hall.

    The louder one plays the music the more annoying it is that the announcer and interval material is transmitted almost as loud as the full orchestra.

    Part of my enjoyment of listening to live concerts is the ability to record and relisten.
    This is gettng better on with iPlayer but the 7 day restriction is a pain.
    The ability to download and keep would be welcome

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  • 15. At 2:03pm on 05 Sep 2010, trevorjharris wrote:

    Wow this anouncement is a big suprise to me. Under Mark Thompson we have seen decline in technical quality both of radio and tv. For years now the BBC has spent millions on promoting the absolutly awfull DAB radio system with it's poor sound quality and it's susceptibility to interference. The net maybe the future for radio as even some car radios have a 3g reciever.

    But why only radio 3. Please can the BBC extend this to other channels some of us would even appreciate radio 4 at 320k. What about some surround sound transmissions as well.

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  • 16. At 4:28pm on 05 Sep 2010, paul_geaton wrote:

    Concur with the other supportive comments, it's a great sound. I have filled in the survey and requested more of the same please. Why not make it standard for online Radio 2, 3 and 4? That would be very much appreciated.

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  • 17. At 4:45pm on 05 Sep 2010, johnlondonw14 wrote:

    Listening to this afternoon's "1910 Last Night" Prom what strikes most now is the smoothness of the sound; there's a lot more "air" around the upper strings and brass on the XHQ 320kbs feed compared with switching back to DAB or Radio 3 on Freeview (with matched levels). Those both sound rough. Particulary apparent on Dvořák's Humoresque.

    Very welcome too are the clean sibilants of the female vocalist and the presenter, not slurring as on all other feeds available.

    Lots of opportunties to hear hall reverb for the Lenonora #3 and it's sounding great withut muddying the direct sound.

    Lots of peak compression on the climaxes of the Wagner Kaisermarsch: did the balance engineer set the levels a bit hot and get caught out at the beginning? (Whoever you are today, thanks to you and all your colleagues and assistants, you do a great job).

    On my equipment, the 320kbps feed is significantly later still compared to both Freeview Radio 3 and DAB. And of course far later than FM, which today is cursed with warbling birdies on my equipment here in West London.

    I'll be listening to the second part on the XHQ 320kbs feed only and forgetting the technicalities. Need I say more?

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  • 18. At 4:52pm on 05 Sep 2010, Mike McMillan wrote:

    I agree with many of the statements concerning the improvements demonstrated by XHD. I am listening on high quality open headphones and concurr - a huge improvement; I am quite used to the acoustic and ambient noise of the RAH as I have spent many hours in there recording the annual School's Proms and this is amply shown up with XHD! Please do keep the service and extend it to cover R3 and R4 throughout the year! I have been dissatisfied with the thinly spread bandwidth available to a DAB multiplex though the potential might have been good with less channels. Keep up the good work - some of your audience really do appreciate it. Mike McMillan

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  • 19. At 6:28pm on 05 Sep 2010, Eric_T wrote:

    To echo other comments, please can we have more of this.
    I have been truly disappointed with the quality of DAB. Frequency response and dynamic range may measure well, but it just sounds wrong. I thought I was just being too sensitive to things until my daughter complained that Radio 5 Live is less acceptable on DAB than AM, despite all the crackles and whistles on there.
    I have been using the 192k internet feed as an alternative to FM, but it lacks some clarity that is there in the FM feed despite some unpleasant multi-path effects that annoy me.
    The time has come for a change of plan. Instead of an all-too-soon analogue turn off, please scrap the current DAB system and replace it with something that provides quality sound.
    This experiment is a major success. The sound is spectacularly better than anything currently available. Can anyone explain why such a moderate increase in bit rate can make even speech sound better?
    Once again, please more of this. It allows me to listen to the music instead of listening to the radio.
    Eric

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  • 20. At 6:56pm on 05 Sep 2010, Mike McMillan wrote:

    Eric_T commented thus:
    Can anyone explain why such a moderate increase in bit rate can make even speech sound better?
    I can only add that though the intelligence in speech may be carried over a narrow bandwith system (such as a telephone line), the natural sound one expects to hear does require far more bandwidth to capture and reproduce. I would go as far as to say that speech requires the full bandwidth like music. I have carried out experiments on data compression for speech and music, speech appears to suffer more than music on some systems!
    Mike McMillan

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  • 21. At 9:08pm on 05 Sep 2010, machare wrote:

    I am delighted with the idea of High Quality sound via the Internet, and I am glad that the BBC is catching up with some of the Dutch and German stations that already offer this.

    There is just one thing that I need and that is a URL than I can enter into vtuner so that my various internet radios - particularly my HiFi system can make use of the service.

    When will the BBC publish a URL for the High Quality stream that an Internet radio can use?

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  • 22. At 9:33pm on 05 Sep 2010, Nethersage wrote:

    Sorry to dampen the enthusiasm, but why is the audio signal passed through a dynamic limiter before being made available as 'extra high quality'? Regarding dynamics, DAB retains the upper hand at present. Do please stop truncating the peaks.

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  • 23. At 10:30pm on 05 Sep 2010, raphael wrote:

    Just listened to the Ulster Orchestra Prom via Proms XHQ through my hi-fi and the sound was fabulous. The most noticeable improvement was in the bass sounds, but overall it sounded far cleaner and superior to DAB, Sky or Freeview, and comparable to FM without hissing or interference. The Last Night festivities should sound spectacular.

    This without doubt leapfrogs DAB and is radio broadcasting for the 21st century - true high definition radio. I hope it becomes the international standard for radio broadcasting. At the very least, it should be back for next year's Proms.

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  • 24. At 10:50pm on 05 Sep 2010, captaintryps wrote:

    I listened to the Mahler, and to the Sibelius and Parry, and I'm sold. This beats anything else on offer, as far as broadcast, downloads and CDs. And I'm listening on a simple £300 radio player with integral speakers. So please make it permanent! And if it's held up by a financial limitation, then cut Chris Evans' hours in half. Or fire all the football pundits. This must go on!

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  • 25. At 00:16am on 06 Sep 2010, rmgalley wrote:

    Friday evening.

    It is very early days so these are only my initial observations and comments. On Friday evening I just had time to extend the decoded bit-stream to the HiFi equipment in the front room and listen on the B&W 801 speakers to the Mahler 1. My only comparison on Friday was FM from Winter Hill (4 miles away). Maybe the occasion was partly to do with it (BPO/Rattle/Mahler 1) but the 320 kbps stream sounded magnificent - the detail, clarity and precision of attack was wonderful. Of course the instruments could heard with great detail and clarity but also the sense of three-dimensional space around them too - wonderful transparency.

    During a quieter section half way through the symphony, I switched over to FM (perfect reception here) and carefully matched audio levels. I was quite astonished at how much dynamic range compression was being applied to the analogue FM feed. It sounded quite squashed and unexciting by comparison. Until recently I had always regarded FM as less fatiguing to listen to and having a clearer sound than any other BBC radio source (including the 192 kbps mp2 feeds on digital satellite TV, digital terrestrial TV and DAB - especially those utilising a 128 kbps bit-rate - UGH!).

    More recently I have come to regard the 192 kbps AAC feed of Radio 3 as superior to FM and the highest quality audio of any BBC radio output. There are still problems with these streams but it is not the the fault of the encoder. Frequently the audio level to the encoder is set too high together with hard limiting of the output to -6 dB of peak level - all the peaks are thus rounded off. This situation is worse on the other 128 kbps AAC network streams where nasty distortion akin to clipping occurs on such as Radio 4 live speech. (The digital TV radio feeds are fed at a more appropriate level and don't suffer from this).

    Also why is it the 'Listen again' feeds are more heavily processed and limited prior to reaching the encoder? They are so much worse than the 'Listen now' live feeds. I wonder how the repeats of these last few Proms will fare in this regard.

    I recorded the decoded 320 kbps stream as a wave file. Looking at it I would still say the audio fed into the encoder was a few dB (6 dB?) too high. During the loud sections everything was hard limited to - 3.6 dB and flattened off (of course FM was much worse in this regard).

    I have yet to make the most relevant comparison. I intend to record both the 192 and 320 kbps AAC streams simultaneously for later comparison but I can only do one at at time on my main PC. Tomorrow I will set up a second PC to download and record the other stream provided the evening broadband contention ratio doesn't foul up the transfer of 192 and 320 kbps at the same time. I normally get a 6.5 Mbps download speed but that hasn't provided a guaranteed solid feed of the 192 kbps stream without the occasional break and re-buffering. I will then to be in a position to do more carefully controlled listening tests to evaluate the hoped for benefits of the higher bit-rate.

    Further feedback pending ....

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  • 26. At 00:21am on 06 Sep 2010, rmgalley wrote:

    Sunday evening update – there IS a problem with levels. Please fix.

    Well, I tried setting up two alternative PCs to record online streams but it wasn’t as straightforward as I had hoped. The on-board audio only gave the option of an already decoded D/A stereo-mix and the audio quality was significantly inferior to that on my main PC. I am going to have to acquire a dedicated PCI card to make valid parallel recordings of the two streams.

    However on Sunday evening I recorded a reference mp2 file from digital satellite of parts of the concert, subsequently converted to a wav file. I also recorded the online streams in real-time as wav files, necessarily one at a time in chunks of 5 or 10 minutes, while listening to them. What was immediately apparent was the much higher audio level of the 320 kbps versus the 192 kbps stream. It is well known when switching between audio feeds the one which is a little higher in level, other things being the same, sounds subjectively better. But here the level discrepancy was such as to have me leaping for the volume control.

    I have established is the 320 kbps stream is 6.9 dB higher in level that either the 192 kbps stream or the digital satellite mp2 feed. Tonight the latter two appear to be within 0.1 dB of each other. The 320 kbps stream is also hard limited to about – 3.6 dB of peak level.

    In the Rachmaninov Piano Concerto on the digital satellite recording the highest level peaks at -5.2 dB of maximum level but the 320 kbps stream recording at the identical point is only – 3.5 dB. Given that the level of the later should be 6.9 dB higher this means the top 5.2 dB of the audio dynamic range is being clipped (OK rounded) off. There is no evidence of peak limiting on either the digital satellite feed or the 192 kbps stream. (Limiters must surely exist to protect against system clipping but the levels fed are appropriate and I have seen no instances of them being invoked).

    Who is responsible for maintaining levels? For this PromsXHQ experiment to have validity it is incumbent on those running it not to have the high level audio bashing the limiters all the time. For the most part their subjective affect is quite benign but, if levels were correctly set, the impairment thus caused would not be a factor in our evaluation. The whole rationale of this experiment is to provide the highest audio quality – subjectively indistinguishable from what leaves the mixing desk at the RAH.

    THIS NEEDS TO BE ATTENDED TO - before we are much further into the trial.

    Other than the above observation I would say the online streams are both significantly better than digital satellite (and, from previous observations, also better than the Freeview radio version). The dynamic range compression I observed on FM on Friday was much more severe than I previously remember and I would have to considerably downgrade its perceived audio quality. The audio quality of the 320 kbps stream, other than as noted above, was a revelation. It has left me needing to find some new vocabulary to adequately express what I have heard.

    More feedback when I have had the opportunity to directly compare the two online streams ….

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  • 27. At 11:07am on 06 Sep 2010, DavidS wrote:

    To add a human perspective, I listened to Prom 66 (Berlin Phil, Wagner etc) on EHQ, the first half on Bose Companion 3 speakers and the second on Sennheiser PXC 450 headphones, and found it more involving than the normal streams. It reminded me of the difference between watching a Prom on HD and standard TV.

    Currently (1025 BST 6 Sep) listening to Sarah Walker Classical Collection. The EHQ stream is perfect, whilst the normal R3 stream has a horrible burbling and lots of dropouts. Not sure how EHQ the content is but it sounds pretty good. The stereo is brilliant.

    PS As of 1105 BST, the standard stream is still burbling but for the brief time it stopped, I was able to make an AB comparison and the difference between EHQ and standard is striking.

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  • 28. At 2:23pm on 06 Sep 2010, David Underdown wrote:

    With regard to message four above - it was a harp string which broke.

    David

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  • 29. At 5:20pm on 06 Sep 2010, Rupert Brun wrote:

    Thanks everyone for the feedback, which is extremely useful. The main concern seems to be clipping of high level transients. Like so many things, getting this right is a matter of compromise. If we have too much headroom we effectively waste a few bits and throw away some dynamic range; if we have too little headroom the clipping becomes unpleasant. We also have to consider what happens to the audio further downstream - every process we apply to a digital signal has the potential to create overshoots which can become clipped further along the chain.

    As well as trying to use the right amount of headroom, we also use good quality audio limiters as protection. For the BBC Proms, there is a limiter on the mixing desk at the Royal Albert Hall, to catch any transients that would clip on the circuit to Broadcasting House. There's another limiter in the mixing desk in the Radio 3 transmission studio (continuity suite) to deal with any peaks here. Both limiters are set to provide protection for high level peaks only, not to modify the dynamic range. The signal is then fed into our Coyopa system for coding at 320kb/s without any further limiting. None of the digital platforms have multi-band transmission processing (compression) on Radio 3.

    Our normal internet distribution at 192kb/s has been well received; the consensus seems to be that the new feed is even better which is very encouraging. The fact that some people are noticing a little peak limiting may mean that we need slightly more headroom at some point in the signal path and we will look at this. Please keep listening and giving feedback; this is a real experiment and I didn’t' expect to get it perfect first time!

    Rupert Brun, Head of Technology. BBC Audio & Music.

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  • 30. At 5:45pm on 06 Sep 2010, Neil wrote:

    personally I think Radio 3 should be 80k MP3,the same quality you think is good enough for BBC Local listen again.

    320k aac should be used across the genre of music styles,not just classical. Rant over!!!!

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  • 31. At 7:56pm on 06 Sep 2010, Mike McMillan wrote:

    Rupert, thank you for your reaction to our feedback; it is indeed satisfying to know that someone is listening (or reading!) to the customers or listeners. I am a sound engineer rather than a computer engineer and though I have a reasonable knowledge of data streaming etc, I am by no means certain I won't put my foot in it, but here goes:
    In a previous posting, I alluded to my dissatisfaction with DAB for although the architechture would allow good audio quality - it is at the expense of bandwidth; sharing the available bandwidth between 3 or 4 channels is fine but with as many as are available on a multiplex, there is much reducing of bandwidth per channel and some in mono only to save a little extra again.
    Using greater bandwidth (thus greater data transfer rates) as you are doing for the experimental XHQ 'Last week of the Proms' suggests to me that you are imposing an increased load on the servers and the infrastructure 'tween you and the listener. If for arguments sake this greater bandwidth were to be used all the time and extended to other networks (R4 for a start), would we then find a dramatic increase in hardware and network speeds is required? What impact might this have (I'm thinking of servers etc.) on the carbon footprint?
    I think I am right in saying that the bandwidth available to you for DAB is restricted by outside factors and though it may be technically possible to provide 320kb/s on 8 or more networks, you are not permitted to use such a large chunk of the available resource for DAB. Will such a restriction disappear when propogation takes place over the internet?
    Regards and Thanks, Mike McMillan

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  • 32. At 7:56pm on 06 Sep 2010, airtiger78 wrote:

    As a long-standing listener to BBC radio -- and occasional critic -- I too have been favourably impressed by the overall sound using 320kb/s AAC: it presented a clearly better spatial quality, but also has some awkward moments of peak limiting. I use a high-quality separate D/A converter to listen to digital sources, through Quad electrostatic loudspeakers.

    The choice between now much compressed FM and very disappointing DAB sound has reduced my listening to Radio 3 in recent years almost to zero. The rise of online availability has to some extent restored my confidence, despite the often irritating presenters whose voices are additionally always far too loud.

    I agree with the comments about speech reproduction. I well remember the early use by the BBC of digital recording of concerts in the late 1970s, when I was surprised by the unexpected improvement in reproduction of the bass end of music and also of the announcers' speech, which at last sounded as good as in live broadcasts. We are (naturally) very sensitive to tiny errors in speech sound; the old pre-digital long-distance analogue distribution lines with their delayed treble frequently produced an effect like loose dentures (as my mother commented).

    One perennial problem for the BBC over the decades has been the battle between sound quality, available bandwidth and sheer intelligibility. This has resulted in the ruination of (successively) basically good AM and FM technologies and also DAB (which I must say started off fairly badly in the first place). AM and FM are now, notoriously, badly compromised in bandwidth and/or dynamics: DAB in its present form varies in sound between simply boring (Radio 3) and downright disgusting (nearly all the others). As has been commented, the ordinary AAC streams sometimes have an inconsistent hard clipping well below peak level, which causes distortion on speech. I hope that this experiment in online high-quality access may be allowed to develop, despite the inherent problem of internet connection quality and continuity (my listening has been interrupted a number of times by network congestion).

    Lastly, I should comment that the realism of Radio 3 sound hereby appears at least comparable with the best of 1970s FM -- I have several nice old off-air tapes (er, cassettes -- with Dolby B :)

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  • 33. At 9:16pm on 06 Sep 2010, Nethersage wrote:

    Thanks indeed for the informative feedback re. the likely source of the limiting some of us have noted, Rupert. Certainly the tonal quality and the clarity of transients is far superior in the 320kbps aac-lc offering to that from DAB. DAB, however, does seem to offer more clearly defined peak dynamics. I wonder if the relative levelling of peak dynamics is something inherent in the Coyopa system?

    I will have a go at using a DAW to make dynamic 'fingerprints' of the same material in 320kbps aac-lc and 192kbps DAB mp2 versions of the same material and post links to them here later, if that's o.k.?

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  • 34. At 00:26am on 07 Sep 2010, Robin wrote:

    Great feed. Currently listening to Jazz on 3. The clean sound here and on the late night Prom immediately before is a real treat to the ears (especially the Prom). The sad effect of the split band processing on the FM feed is all too clear on direct comparison.

    Let's hope that the BBC decides to keep the XHQ feed for Radio 3, and fine-tunes the level issues.

    (But isn't it sad that one can't listen to a studio quality feed on Radio 3 FM?)

    And many grateful thanks to those who made the experiment possible.

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  • 35. At 00:52am on 07 Sep 2010, rmgalley wrote:

    Thank you very much Rupert for your feedback back to us. It is greatly appreciated.

    While I agree it is very important to optimise the levels to take advantage of the dynamic range available and, at the same time, not incur any signal clipping, I don’t think this is the problem here. All the digital transmission paths available to me (digital satellite, terrestrial Freeview radio, the 192 kbps/320 kbps aac streams and also the infamous DAB) utilise 16-bit resolution with 48 kHz sampling. They must all have hard limiters to avoid full scale peak level clipping. The problem simply appears to be the level being fed on the 320 kbps stream is 6.9 dB too high.

    This evening, on my main PC, I recorded Radio 3 from both digital satellite and terrestrial Freeview as mp2 files simultaneously while, at the same time the decoded 320 kbps aac stream as a wav file. The mp2 files were later transcoded to wav files. On another PC I recorded the 192 kbps aac stream also as a wav file.

    The later was transferred to the DAW on the main PC and all the waveforms examined. This revealed the levels on all transmission paths matched to within 0.1 dB with the exception of the 320 kbps aac stream (I didn’t look at DAB or record FM). The 6.9 dB higher level here would have caused system clipping had it not been for the intervention of the hard limiters.

    I can only speculate and surmise but presumably the linear uncompressed link (probably 24-bit resolution?) between the RAH and BH is common to all the digital feeds and streams. It cannot then be the limiters on the output of the mixing desk of the OB vehicle at the RAH. Currently, although the experiment is called PromsXHQ, the high bit-rate stream appears to be running 24/7. So the output of Radio 3 Continuity is being continuously fed to the Coyopa coder but somehow the level is being raised by 6.9 dB and this higher level audio content is continuously hitting Continuity’s limiters? It is almost indicative of an un-terminated signal path somewhere in the continuity desk.

    Notwithstanding the technicalities, this evening demonstrated another wonderful listening experience. The Beethoven Piano Concerto 5 was a delight and, for the most part, I forgot about the limiting problem as so much else was benefiting form the greater openness and clarity of the sound. We must surely be hearing sound indistinguishable from that at the output of the RAH mixing desk – all it needs is the level/limiting problem to be attended to.

    I wish to heartily thank Rupert Brun and his team for making this possible. In the past the BBC stood for technical excellence but of late this image has become severely tarnished. The DAB fiasco is a case in point. It is a great pity radio spectrum has been sold off so it will never, in the future, be possible to broadcast such high quality audio and receive it on a radio via an aerial. Internet radio is definitely in the ascendancy now.

    Someone else has commented the degradation to FM by dynamic range compression and the inferior sound of the UK mp2 broadcasts had reduced his listening to Radio 3. I too have spent a lot more time listening to the 320 kbps mp2 German classical satellite stations – after all language isn’t much of a barrier for classical music – but the introduction of high quality streams on a permanent basis would change all that. Here’s hoping.

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  • 36. At 06:27am on 07 Sep 2010, johnlondonw14 wrote:

    It’s great that this experiment is continuing and I hope will become permanent once the teething troubles are shaken down.

    I already use the different feeds for different purposes and this increases my listening to BBC Radio overall:

    FM/VHF is great in a car, where I am glad to have the benefit of a high-quality and sensitively-managed compression chain rather than something provided by a car manufacturer that has to suit every audio user of every taste. I won’t be throwing away my VHF/FM receivers just yet precisely because it offers a sensitively compressed version of the programme which is useful for casual listening in a car and around the house.

    DAB has an option for dynamic range encoding at source but my experience is that this is relatively primitive.

    How wonderful that we now have available at home something even closer to the sound as heard by the balance engineer, without the physical constraints of working on location or the distractions and responsibilities of that job.

    Let’s remember these different audiences and their needs, treasure the extra high quality feed and enjoy it for concentrated home listening but not abuse our privileged position in the BBC’s data budget. The listener who is commenting on the low data rate of local radio has a point. And let’s not forget that the BBC is currently fighting to balance its financial budget and that DAB initially launched with Radio 3 at 320 kbps albeit with an mp2 codec which the more sophisticated AAC codecs have been designed to improve upon. That privileged position was eroded due to politics. I anticipate we’d find that 320kpbs mps would not sound as good as 320kbps AAC.

    There used to be a method of working where the balance engineer listened off-air and balanced including the entire transmission chain, out to the transmitter and back. That made the fullest use of the transmission channel. That way of working stopped some years ago but was commonplace when the NICAM distribution chain was first introduced so that the limiters doing most of the work were the NICAM input limiters and everything prior to them in the chain was analogue. Those days are gone now and that way of working is probably infeasible now due to the codec delays. But some of our treasured home recordings will have benefited from this technique.

    What’s my point, get it right for Radio 3 and then hope that the BBC can find ways for this experience to benefit all audiences

    There remains the problem of how to connect a computer to the hi-fi equipment. Clearly some of us have arranged this successfully already. I have been horrified at some of the arrangements used by my less-technical friends and this has come to light particularly after tipping them off about this experimental feed over this past weekend.

    Problems of earth loops (there’s a real safety issue here with inexperienced people lifting earths to try to reduce buzz), fan noise, induction noise from screens and of course hard disc noise.

    There’s a gap waiting to be filled of a realistically-priced receiver unit to deliver really good audio from the internet to domestic audio equipment.

    Meanwhile, some guidance on air would be welcome: maybe an item for “CD Review”?

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  • 37. At 11:58am on 07 Sep 2010, Rupert Brun wrote:

    As @mgalley has pointed out there's a level problem at times with the experimental feed. I want to apologise for this - it's an experiment, I knew we would learn a lot but this is a problem I wasn't expecting. We carefully set the levels to match and when we check again later, there's sometimes a difference of 6dB. The engineers are working on this but pinning down exactly what is causing it is taking a little while. Our main transmission chains are duplicated, as is the Coyopa system, in order that we can undertake maintenance and upgrades without falling off the air. There are a large number of interconnections between the various items of equipment and so the whole system is quite complex to trouble-shoot when intermittent problems arise.

    Rupert Brun, Head of Technology, BBC Audio & Music.

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  • 38. At 1:02pm on 07 Sep 2010, David Samuels wrote:

    May I just add my thanks to Rupert and the team for allowing us to take part in this experiment? I use a laptop to feed a line level signal to B&W 805s via a pair of Arcam amplifiers and I consider the resultant sound to be at least as good as from my best CDs. If this feed were to become a "production" offering, I'd spend money on a proper, silent, source.

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  • 39. At 8:30pm on 07 Sep 2010, cantobel wrote:

    Listening to La Mer. The 320 stream is running almost 7dB louder than the 192 stream, and not surprisingly the high level transients are ruined, everything ruthlessly clipped at -4dB. On the 192 stream, there is no visible or audible sign of limiting. Please, please sort it out. This is the only thing (plus a couple of momentary dropouts) spoiling an otherwise wonderful audio experience.

    Actually there is another problem. Question: How do you make one person sound louder than a whole symphony orchestra? Answer: By making her a Radio 3 announcer. She is too damned loud, by a factor of at least 2.

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  • 40. At 9:54pm on 07 Sep 2010, Nethersage wrote:

    cantobel, by "the 192 stream", do you mean the 192kbps mp2 stream offered by DAB, Freeview and satellite? If you mean the standard iPlayer stream, I think you will find that that is now 128kbps aac, though 192kbps mp3 is used for the iPhone version of the 'Listen Again' iPlayer file.

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  • 41. At 10:25pm on 07 Sep 2010, Nethersage wrote:

    By the way, those contributing to or just reading these comments might find the discussion at:

    http://www.bbc.co.uk/dna/mbradio3/F7497566?thread=7737460&skip=0&show=20

    to be of interest.

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  • 42. At 10:32pm on 07 Sep 2010, cantobel wrote:

    Nethersage, as far as I can see, the live AAC Radio 3 stream (which is what I was referring to) is at 192kbps AAC, just as it always is. The other national stations are at 128 AAC. The Listen Again AAC Radio 3 stream shows as 128, though I have been assured it is actually also 192. Freeview and satellite R3 are always 192kbps mp2, DAB R3 is usually 192 mp2, sometimes 160.

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  • 43. At 10:56pm on 07 Sep 2010, Nethersage wrote:

    Ah, shows how often I access the live version of the iPlayer for Radio 3. I had assumed the labelling of the 'Listen Again' version as 128kbps aac was correct, and would also apply to the 'live' offering. Clearly not, as I have just observed. Strange about the 128kbps label on the 'Listen Again' version though.

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