This links with Sound Levels since 1961: the two pages overlap to a lerge extent.
Patrick Heigham
I remember being told that PPM6 was the upper limit as anything over could take the transmitter off the air, and anything very low for a period of time, had to be advised to CAR, in case they thought that the signal chain had been broken.
There was a BBC film (shown at Wood Norton) showing the different displays between PPM and VU meters.
I once had an energetic argument with a film re-recording mixer over the dynamic range between broadcast and film soundtracks. On the PPM scale for broadcast, this is around 26 db, film is considerably expanded, and if I’m viewing a Blu-Ray disc, I am constantly altering the playback volume.
I never really understood compression, whereby the commercials always seem, perceptively, louder than the programme either side.
My run-about SQN mixer had brilliant limiters – you could not hear them operating, but I had them adjusted to cut in at PPM6 rather than the 5 1/2 factory setting.
Chris Woolf
The BBC hated VUs with a vengeance, having been instrumental in designing PPMs. Thus they consistently aligned them incorrectly and then demonstrated "how bad they were" to prove their point. In fact, correctly aligned VUs have always given a better indication of loudness than PPMs, which is why the music industry has got on with them rather well. The waggling VU is an unattractive indicator to use in the modern digital world, but so too is the analogue rooted PPM – both are superseded now.
Wonderful though the BBC engineering department was it should also be recognised that it was well-versed in propaganda too: not everything they promoted was the whole truth, and there were many truths they never mentioned.
Dave Plowman
But it makes no difference what sort of metering you use if no one bothers to look at it – or understand what it does.
Patrick Heigham, Chris Woolf
I would surmise that desks nowadays have bar-meters, which were adopted by domestic machines a while ago. Clearer to read, no doubt with the colour change, but what law do they follow?
Loudness – EBU R128, BS1770 etc – there’s a lot of stuff on the web to read up. With digital signals the true peak needs to be metered, not the short-term one that an analogue PPM could manage, but in addition the audience is much more interested in how loud the programme sounds. Programme now gets measured in loudness units (LKFS Loudness K-weighted Full Scale). The industry isn’t quite there yet but is at last heading in the right direction.
Usefully, loudness metering (and even correction) can be run on a digital audio file the point about nobody looking at a meter can be defused to some extent, although you need at least one ear and brain initially.
I’m fully aware that in the cinema, dynamic ranges are used for effect, but those are unsuitable for home consumption.
That’s where loudness metering has some advantages. If you just push everything to give maximum welly, as has been the habit in the film and music industries, loudness monitoring simply drags the overall signal down to give a rather flat, limited dynamic range sound track. Handle everything a little more delicately and a more interesting dynamic range becomes available that doesn’t deafen you or the neighbours, but does allow some colour into audio tracks again.
Alasdair Lawrance
The fact remains that the end result in the home is not satisfactory. How should broadcasters solve the problem? Is it just down to enforcing certain standards, which seems to be lacking these days? There must be a proper mix somewhere, if programmes, (rather than formats), are being touted for sale.
And sound when we hear it is analogue, is it not? Or am I missing something?
Dave Plowman
I keep on reading about these super duper loudness meters being in use – but if anything, with TV sound, things have got a lot worse in recent years. And not just on the ‘minority’ channels where I suppose they can be expected to cut corners due to costs. And frequently show legacy material which has likely suffered from poor transfers down the line.
The only thing I can think of in recent years which did address many complaints was restricting the peak levels on commercials on ITV 1. They are now not allowed to peak more than PPM5. And on ITV 1 at least no longer blast you out of the room, in general. The main offenders are more likely to be continuity announcements.
For what it’s worth, if I can be bothered looking at a PPM on the progs I complain about, that always shows why I’m complaining.
Everyone I know who has experience of both PPMs and VUs for broadcast use prefers PPMs. Of course those who only know VUs – perhaps most of the world – will automatically prefer them. Even Nagra didn’t find a plain VU suitable for recording to tape.
It’s not helped by digital having that 10 dB headroom. Fine if everyone adheres to it – but they don’t, and even a plain mistake can result in having to reach for the ‘volume control’.
My feeling has always been a PPM (and knowing what it reads) combined with trained ears are an adequate way of setting levels. I’m happy to concede that there could be a simpler device which could be read by non trained personnel. But I’d ask what non trained personnel are doing being in charge of sound levels anyway.
I go to the cinema pretty regularly. The most recent films I saw were mainly speech based rather than ‘action’, sound wise. I go on a Tuesday afternoon and the cinema I use is pretty quiet at that time. But they play the soundtrack at far higher level than I’d like.
Dave Buckley
The last film that my wife and I went to see was “Star Trek Into Darkness” with Benedict Cumberbatch in it (released 2103). After about 10 minutes my wife said that she couldn’t stand the sound level and left.
As she complained (and got a refund) she was told that there had been quite a number of complaints, but that the management couldn’t do anything about it as they weren’t allowed to alter the sound level! (Now where did that one come from?)
I think the problem is that cinemas don’t take into account the size of the audience. If the auditorium had been (say) three-quarters full, then the level would probably have been OK due to the absorption factor of the audience.
Incidentally, has anyone heard of the ‘popcorn’ effect? Apparently with some films there were complaints that the track couldn’t be heard in some places. This was traced to the ambient sound levels in cinemas due to people rustling sweet papers and eating popcorn! I understand that mixing for feature films now takes this into account – (background tape of said sounds running in the mixing room?).
Chris Woolf
It’s a mistake to assume that the great number of VU users around the world were in ignorance of PPMs. That was very much BBC indoctrination, but a majority actually preferred the VU because it correlated better with perceived loudness.
There’s no argument that PPMs were excellent devices, and were superior to VUs for preventing the over-modulation of analogue transmitters. They tended to suit European attitudes towards engineering too. However the great majority of classic music recording, and a vast number of superbly balanced film and TV productions around the world were produced using VUs and probably benefited from it.
Both meters are sadly lacking in the digital domain – they just don’t show the parameters we need to know now.
Loudness monitoring has only just started to come in. It isn’t fully integrated into productions, and a lot of radio and continuity hasn’t embraced it yet. But there seems little doubt it will eventually take over everywhere. Even iTunes and Spotify are using it, and the rules are essentially the same in the EBU and SMPTE world – first time ever for that. It will take time, but it is in everyone’s interests for it to become universal, not least because it can be automated – so it even satisfies the suits.
The problem with analogue PPMs is that they integrate peaks for 5mS. They don’t show true peaks, which is pants in a digital environment. PPMs are also lousy for giving a hint of loudness – you can fool them very easily. Ears are good with a little calibration and they do work extremely well with loudness monitoring – they agree so well that ears and meters match almost perfectly after a few minutes.
Digital signals don’t really have "10dB headroom". An analogue PPM could under-read transients badly so PPM6 indication could actually mean very close to 0dBFS. Hence one had to allow 10dB room to cope with unmeasurable stuff – a pretty silly arrangement. Loudness meters with a true peak indication let you always prevent overloads, but you don’t have to stick to any arbitrary maximum such as PPM 5, 6 or 7. If it’s a massive crowd roar you can let it run up to an accurate -1dBFS, so long as the rest of the material is quiet enough to keep the long term level around -23 LUFS.
The good bit about loudness monitored programme is that it actually sounds a lot better than the heavily compressed stuff, rammed as close to the legal limit as possible.
Give it all a year or two to get there…
John Hoare
The point is – PPMs aren’t about loudness, they are about keeping within permitted levels. I think there is a genuine problem in that good ‘film’ style drama is made with a wide dynamic range, with some effects much higher level than most speech. This is great (neighbours allowing). However, an advertisement hitting sixes all the way through is an abomination. The problem is that the simple approach of nothing over six doesn’t do the job any more.
The length of time a clipped transient has to last to be noticed is something which is a bit of a dilemma, but to maintain standards meters have to be made to an agreed spec. I think that most digital era PPMs have a red overmod LED which catches the short peaks that the meter (analogue or digital) deliberately doesn’t – it will sometimes flash on at PPM 5 and be off at PPM 6!
Nostalgia buffs click on this link to find your very own BBC PPM in software. It’s brilliant – the needles even kick like a real one when it comes on! –http://www.darkwooddesigns.co.uk/pc2/meters.html
Chris Woolf
In the analogue world clipped transients weren’t a worry, so long as they were "short". at worst they tizzed slightly. In the digital domain that isn’t the case. Even a few samples of digital clipping can produce some disgusting effects under some circumstances, and worst of all it is possible for "maximum count" samples to understate the true peak level by up to 3dB.
Thus "true peak" meters must be proper digital devices that over-sample the audio by >=4 times and reconstitute the signal as it would have been if it hadn’t limited.
Analogue meters with or without LEDs can never manage this.
Dave Plowman
In the ‘analogue world’ noise was usually a problem – especially with tape recorders of both the audio and video sort. Hence the importance of keeping modulation levels reasonably high.
With digital, it isn’t. So why the necessity to still peak to maximum? You simply set the maximum level in practice some way below the theoretical peak – exactly as the EBU did when digital recording arrived. That figure was 10 dB – so a metering under read of 3 dB would cause no distortion.
Of course this ‘artificial’ peak level needs policing – otherwise plenty will ignore it in the quest to make ‘their’ sound louder. I’m afraid no loudness meter will make the slightest difference to those types, as they will simply ignore it as they ignore a PPM.
Jeff Booth, Philip Tyler
What probably happens (at least that was my experience at C4) is that the advertising agencies buy one of the latest meters and mix their ads so they get as close to breaking the rules as possible (without the ad actually failing QC).
There will always be a way to bend the rules. Advertisers will go to any length to make their adverts stand out, BBC trails did a similar thing.
After all, with a PPM a whisper can peak PPM6. So can a heavily compressed rock concert. Which sounds louder?
Dave Plowman
All true. This makes relying on any ‘meter’ – no matter how ‘clever’ – rather pointless. Of course cynical me says a ‘meter’ is a cheaper option than a trained pair of ears, so very attractive to the suits. And likely to be promoted as the answer to everything by those who sell such things.
Of course there will be subjective loudness differences between a brash pop show and something like talking heads. It’s when two apparently similar talking heads progs make you reach for the volume control that things have gone very wrong.
Chris Woolf
The point here is that the delivery "agent" is the one with the automatic system that checks and corrects loudness levels.
A producer can turn up the levels as high as he/she likes but that doesn’t do any good. The play-out system reads the file loudness and merely winds the level down to be the same loudness as everything else – it’ll just tend to sound duller because it has a lower dynamic range.
That’s why broadcast, streaming and other delivery system owners are far more interested in the concept than they were for manually levelled stuff. With loudness the computer can say "no". No effort on their part, no personal judgement, stuff it in the server and let that do the work. And far fewer complaints from the customers about having to leap for the volume control.
Of course it won’t cure mumbling and poor music balances…
Dave Plowman
It will be interesting to see how it works on live programmes. My personal view is that it is a way of ‘sorting’ a very rare problem while ignoring the main one.
Patrick Heigham
When I was working into DigiBetacam, I set the zero level from my SQN (PPM4) at -18 on the camera’s bar meter.
Post houses seemed to be happy as we also idented the tapes with tone described at PPM 4 – I’ve no idea whether they were using PPMs on the desks or not, but never had any complaints about over or under modulation. The SQN, for doco work, was simply very good. The limiters could not be heard working, and I had my unit recalibrated for the limiters to kick in at PPM 6 rather than the factory setting of 5 1/2.
Doco work could be exciting as one didn’t really know what you were going to get, and this was without a rehearsal in a lot of cases. (Doing a doc on the working of Gatwick Airport, we shot a sequence of all the fire engines deploying at once – all bells and whistles! I hopefully asked for a sound rehearsal – no! Covered myself by splitting the mic between the 2 tracks with one set at least 10db lower than normal, in case my usual judgement was way out!).
I think the SQNs were available with various EBU scales, depending on the country. Working in the (then) East German Berlin Parliament, and tapping the PA feed, the in-house engineer said he would send zero level tone for me. Wound the pot to its usual position for a line input, and blow me – spot on PPM 4! They were using Tuchel plugs for the distribution and he produced a Tuchel to XLR jumper!
Dave Plowman
If I recall correctly, that is standard EBU lineup for digital: +8 above ‘0’ level gives you PPM6, ie maximum, leaving 10dB for headroom – to allow for an analogue meter under reading in some conditions – and mistakes.
It’s also how TV sound is ‘lined up’ on FreeView. The majority never exceeds -10dBFS. Trouble is it is possible to do so – and an extra 10 dB of level will get near anyone reaching for the volume control. It also explains why radio on FreeView via FreeView is so much louder, as they (or rather some) peak to 0 dBFS, Just try changing channels from BBC1 to say Magic Radio.
Basically, this is the sort of nonsense that needs addressing. And some clever meter isn’t going to show it any more than a PPM or even VU.
Brian Curtis
According to this piece I found in the BBC Academy on "Loudness" (which seems a very good description of the difference between Peak Programme Level and Loudness by John Heraty, a BBC broadcast technology trainer) all Programmes and Trails should be recorded/mixed/set to a -23 LU (LU = Loudness Units)
http://www.bbc.co.uk/academy/technology/broadcast-technology/loudness/article/art20130716141928123
Why isn’t this happening?
Mike Felton
Because the Beeb is in a frustratingly slow transition phase, i.e. some programmes are made to “R128” standard but some are still playing by the old PPM6 rules.
Some broadcasters are fully R128 compliant, e.g. Sky, and BT have been since they started. The Beeb as it is now constituted seems to lack any firm department with authority to make people comply. Ironically the worst offenders of being too loud are trails and (particularly) the live continuity announcers – both of which one would think are within the BBC’s control! Although the trails will apparently be complying by Christmas but the con anncts are still a “work in progress”.
If you don’t know what all this is about I recommend having a look at the videos of a recent IPS meeting on Loudness held in NBH with cooperation of BBC Academy. The link to them is on the front page of the IPS website www.ips.org.uk
Operationally the crucial step is to establish a monitoring level to match the target of -23 LUFS and then essentially mix by ear with only occasional glances at your “I” (integrated) reading which is the running average of the whole programme. It is actually liberating mixing with a higher dynamic range. My mixes have been within R128 spec for more than a year without a PPM in sight.
If you want to experiment with a loudness meter you can download one and run as a demo on your laptop. My favourite is VisLM-H by Nugen.
Dave Plowman
It’s quite rare to have problems within a single prog, obviously excepting accidents in a live prog or whatever.
The problem as I see it is progs balanced by different people. And, of course, those made many years ago which could have suffered from a careless transfer at some time.
Apart from the odd one like “Jamaica Inn”, the vast majority of major productions (nowadays (2014)) seem just fine here in terms of actual levels or ‘loudness’. It’s differing levels between progs, and trails and ads and continuity which most people complain about.
I’ll generally wind up the wick for one of your superb Jools (“Later … with Jools Holland”), since I prefer pop music at a higher level than drama, but what annoys me is having to adjust levels between two similar speech-based progs.
