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back to article High-powered luvvies given new radio home: 'But DON'T disturb the neighbours'

Production companies will be allowed to operate 10-watt radio links in Channel 38, now that Ofcom has established it won't annoy the radio telescopes operated by nearby countries. Having shuffled the rest of the Programme Makers and Special Effects (PMSE) out of their existing home in Channel 69, in preparation for flogging that …

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Silver badge

"one example being the Golf Open when commentators needed to be near the action, but get quality audio back to the club house for transmission - but when they are used there's generally no alternative."

Not a good example - this is a voice commentary, so it doesn't exactly need to be super-duper highest possible quality, all they need is for the words to be intelligible. A mobile phone or walkie-talkie should work fine! And given that the news channels seem to think that a bad skype link is okay for interviewing people, then surely similar quality is fine for some sports commentary?

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I don't think the problem is the bandwidth quality: It's the transmitter power.

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I agree it seems like not the greatest example. Exactly how much latency does going digital and would this significantly impact such a fast paced sport like golf?

I have no horse in this race, just interested as it struck me as odd. Especially as you could add a slight delay to the pictures as well to bring them closer to sync (I assume we are talking a sub second lag). I could understand the bar flies in the clubhouse perhaps noticing a half second gap between commentary and video feed, but surely the video feed also experiences some delay in transmission \ conversion?

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Anonymous Coward

Golf balls

You don't think the viewers (and those paying the BBC for syndication rights?) would get a bit upset if they saw the stick hitting the ball, and picture shows the ball going in the hole, whilst the sound of the stick hitting the ball then going in the hole and the crowd applause followed on half a second or more behind the picture ?

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Plenty of other applications use digital transmission, with timecoding and a small buffer they can be synced. The article actually mentioned relaying commentary to the clubhouse for transmission but the cameras filming the action use digital transmission so it smells a bit funny that the audio cannot as the video will have significantly more information.

Also calling the quality of the audio into question is a little odd. Even losslessly encoded digital would allow for more information and a greater sampling rate, in theory increasing the quality. It just sounds odd thats all :-)

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I might be showing my ignorance here, but what if the production company wants to work on location in one of these countries that still use Channel 38 for their telescopes? Is it easy to flip to new more appropriate channels?

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Wireless gear that isn't complete crap usually has a setting to change it to a different frequency. That and production companies are required by law to use equipment that has been certified by the proper authorities of the nation where they want to use said equipment.

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The weakest link

> High power users ... can't go digital because of the same quality and latency issues that prevent the entire PMSE industry adopting digital radio

Yet all our domestic TV manages quite well with digital transmission to the viewer. So I can't see the point in having higher quality "upstream" than the user is capable of receiving. If the signal was digitised as soon as possible, there shouldn't be any further loss in quality all the way through the chain, from O/B to the viewer, provided that the signal wasn't reconverted to analog at any point.

Has this premise about quality and latency ever been tested, or is it just the doom-mongers putting up roadblocks as an excuse for not wanting to make changes?

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Re: The weakest link

You seem to have missed the point, it is not latency for "live" broadcast on TV - that is bollocks, it is latency for things like concerts and theatre where you can't tolerate 0.1s delay between actors & instruments, etc, and those involved are experiencing it all in human real time.

All of the bandwidth/power gains you see with digital radio come at the expense of delay - you need to have a significant block of data (10s of milliseconds or more) before you can strip out 'insignificant' information for audio compression, and similar case to allow the addition of worthwhile forward error correction (ARQ is largely a lost cause when real-time matters, and most radio mics, etc, won't have a back channel).

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Re: The weakest link

Um. Broadcast digital TV is compressed with lossy compression (MPEG2/MPEG4) and the quality isn't really that great (it's compressed to the point that it is "just good enough"). You don't want any lossy compression on the production side because every bit of processing would result in recompressing and maybe even resampling with further loss and this degrades quality.

Try ripping an MP3, burning it to CD, ripping it back again with slightly different parameters, and repeat the process a couple of times. The quality will drop drastically even though every stage of the process was a digital recording...

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@Paul

> like concerts and theatre where you can't tolerate 0.1s delay between actors & instruments

It's a long time since I dabbled in TV (university course, back in the analog days), but I do seem to recall being told that to make the audio sound "right", there's an artificial delay of some 100's of mSec introduced specifically so that actors lips move at the same time that the sound reaches the viewers ears.

So long as the right amount of delay between sound and vision is introduced, and kept constant the absolute time delay between recording the "live" event and the time it makes it through to the TV is immaterial. I often notice that in our house a TV tuned to a terrestrial channel leads another TV tuned to the same channel on satellite (not surprisingly) by a second or two.

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Re: @Paul

"specifically so that actors lips move at the same time that the sound reaches the viewers ears"

I expect that delay is the opposite way - you delay the video to account for the audio's slower path.

The real problem is for the actors & musicians who need to play in time with each other, and if you remember the joys of significant delay on a phone, it can be very disconcerting (pun?) to hear yourself with a modest delay.

What Ofcom has finally been forced to recognise it seems is you can't magically replace a high power FM link and get the same near-zero delay and hi-fi sound in a GSM channel, and so live events need to have much more bandwidth (and protection for it) than a similar number of phone users.

The issue behind the shift is simply money - they wanted to combine and flog the analogue TV spectrum for money. Ah yes, analogue TV, I remember when it was near real-time for the New Year bells and where you did not get blocky compression artefacts on anything fast moving. Just needed a decent SNR...

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If there's any danger of interfering with radio astronomy

Then astronomy has to take precedent.

Science > performing arts

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Meh

The alternative view..

Radio Astronomy? How much advertising does THAT bring in?

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Happy

Re: The alternative view..

Have a look tomorrow night when live radar pictures of approaching doom are broadcast from Jodrell Bank...

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Bronze badge
Go

Re: The alternative view..

But better make it cash-in-advance, and spend it all on nifty funerary goods for a happy afterlife. Wiki sez that the Mayans favoured "mushroom figures" among other things so something like this but made of platinum:

http://4.bp.blogspot.com/_lGw8sYiLP5U/SqVkG9eNqTI/AAAAAAAAAEw/4YF-C7h8_Dw/s1600-h/pilzSmall.jpg

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