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Please help me decipher this audio supply spec! PPM / BS6840
Old 7th May 2019
  #1
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Please help me decipher this audio supply spec! PPM / BS6840

I am supplying a music file to be shown at a festival, the organisers have circulated this spec, I can't decipher it, despite googling - seem to be several standards and I don't know which is which. I am assuming that my music falls into the bracket of 'Compressed Music' (see grab), here are the specs. Can anyone translate this into RMS / LUFS / Peak etc please - I'm baffled
• The following spec uses Peak Programme Meters (PPM). The Maximum or Quasi-Peak Programme Level should never exceed 8dBu above the programme’s reference level.

• Please adhere to the following levels, as measured on a PPM meter to BS6840:

•Compressed Music (depending on degree of compression)
Normal PPM - 4
Peaks Full range 2-4
Attached Thumbnails
Please help me decipher this audio supply spec! PPM / BS6840-screen-shot-2019-05-07-11.45.36.png  
Old 7th May 2019
  #2
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I found this very handy free meter mvMeter2 from tb-software.com
It has a PPM (BBC) setting, so could be problem solved, although it seems like quite an approximate measurement of loudness? Is PPM pretty old school?

p.s. I'm not a mastering engineer
Attached Thumbnails
Please help me decipher this audio supply spec! PPM / BS6840-screen-shot-2019-05-07-12.56.02.png  
Old 7th May 2019
  #3
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Hi,

that's strange delivery spec. for festival, because it usually doesn't make much sense to have such requirements for some projections or playback at live events (which is typically mixed anyway at FOH with speech).
Maybe they're counting with use for some kind of reel from supplied clips, but that's just guess.
Because all those specs. are basically just copy-paste from old documents for delivery to BBC for broadcast. Well there it have its reasons.
TV or radio broadcasters typically use classification of programmes with different recommended (or enforced) dynamic range according to intended use.

PPM (or quasi-peak metering) was a thing coming from analog world, which was superseded by current standardized loudness measurement and true-peak metering.
Also it was really a mess internationally, because different countries adopted meters with different scales and ballistics.
Check the table at p. 2 in https://tech.ebu.ch/docs/techreview/...ofski_klar.pdf
The British one was IMO weirdest ( or the most special, I always like all those apparent oddities ), because one step at PPM scale is 4 dB.. and when you fed it with alignment/test tone (-18 dBFS in digital domain), then it reads 4.

Of course in digital domain, there is no 8 dBu max. or so. And this spec is pretty much worthless for DAW alone. Max. permitted level for this PPM and broadcast is 6 (with those odd units, so its 8 dBs above test level.), which translates to -10 represented in dBFS. The mvMeter2 has that right, so you can simply use that as a reference.

With regards to mentioned dynamic range.. there is quite unconventional term - full range peaks vs normal.
What that means is, that PPM meter readout during programme playout should be within region they specify as full range (eg. 2-4) and with majority of "normal" peaks landing at 4 for their "compressed music" category.

You can check page 37 in this book.
https://books.google.cz/books?id=FS2zAQAAQBAJ&pg=PA37

Generally, I think, there is just some ex-broadcast engineer, who has those specs somewhere in drawer from early 90's
Otherwise, it's just unnecessary complication for anyone involved.. if he would specify that with integrated loudness and dynamic range (according to R128), it will be much clearer.

Michal

Last edited by msmucr; 7th May 2019 at 06:11 PM.. Reason: English, phone, sorry :)
Old 7th May 2019
  #4
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Thanks Michal
That’s really helpful. The video is for Oxfam - it will be played in between bands, with other info videos so I guess they are trying to standardise loudness but I totally agree that it seems the wrong way to spec it.
I will investigate.
Thanks again
Ted
Old 7th May 2019
  #5
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Hi Ted,

I came to DAW finally and just for curiosity, I've tried mvMeter.. I usually use it for plain VU, but briefly tested its PPM readouts (I don't need to measure that normally).
Scale is right, but unfortunately I believe, its PPM mode overreads with short peaks, eg. there is too short integration time for valid metering according to the standard.
I wrote to Thomas at TB Software about that issue.

So in the meantime, if you need PPM meter to meet the specs, please get TripleMeters by PSP.
http://www.pspaudioware.com/plugins/...p_triplemeter/
The red mode (those are switchable with arrows around central text at UI) seems to be PPM meter with correct times and ballistics. They have fully functional 14-day demo.

Michal
Old 8th May 2019
  #6
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Quote:
Originally Posted by msmucr View Post
Hi Ted,

I came to DAW finally and just for curiosity, I've tried mvMeter.. I usually use it for plain VU, but briefly tested its PPM readouts (I don't need to measure that normally).
Scale is right, but unfortunately I believe, its PPM mode overreads with short peaks, eg. there is too short integration time for valid metering according to the standard.
I wrote to Thomas at TB Software about that issue.

So in the meantime, if you need PPM meter to meet the specs, please get TripleMeters by PSP.
http://www.pspaudioware.com/plugins/...p_triplemeter/
The red mode (those are switchable with arrows around central text at UI) seems to be PPM meter with correct times and ballistics. They have fully functional 14-day demo.

Michal
Great, thanks Michal.

I bounced out a couple of versions last night using mvMeter PPM (one at '4' and one at '5') - it seems that using PPM is open to a bit of interpretation from the user, because it doesn't really produce a steady average reading, so the client could end up with quite variable loudness using those supply specs I put in the first post?

Normally if I have to supply at EBU r128 or ATSC A/85 I simply put it through my TC Electronic LC2N plug and it gives me the correct spec in seconds!
Old 8th May 2019
  #7
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Ok I installed the PSP Triple Meters - it gives a more steady reading compared to the mvMeters, which makes the PSP much easier to use.

However, the default ref level of Triple Meters is -12dBFS (4PPM), but the ref level of mvMeters is -18dBFS (4PPM).

I adjusted the ref level of the Triple Meters to -18, but it's a bit weird that the default is -12 isn't it? I would expect the default to be the standard.

Ted
Old 8th May 2019
  #8
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Quote:
Originally Posted by tedmanzie View Post
I bounced out a couple of versions last night using mvMeter PPM (one at '4' and one at '5') - it seems that using PPM is open to a bit of interpretation from the user, because it doesn't really produce a steady average reading, so the client could end up with quite variable loudness using those supply specs I put in the first post?
Yes, that's indeed the very problem of those PPMs with regards to practical use.
Generally audio meters are used for two basic reasons, to avoid some technical issues (overmodulation, clipping) and to help with levels and balancing during mixing or classification of material.
PPMs were primarily aimed for the fist task in the era of analog broadcasting. But given its integration time (10 or 5 ms depending on standard), it's bit too slow to indicate instant clipping in digital. So that's why it needs quite significant headroom (cca 9-10 dB bellow full scale) above max. permitted level when mapped to digital domain to avoid problems.
For leveling duties it's too quick. Being pseudo peak meter, it really doesn't tell you much about average levels, which are much closer to our perception of loudness.
I recall, when I started more seriously with audio in 90-00's, it was pretty much standard practice, that people commonly used two kinds of meters at the same time. Some quick PPM (like RTWs with orange plasma bars) to check analog peaks to meet delivery specs and old needle VU meter for slow averaged response (sometimes modded to be even more sluggish).
I can of course also recall arguments with QC and dubs people.. who has the right meter and who has misalignment

Quote:
Normally if I have to supply at EBU r128 or ATSC A/85 I simply put it through my TC Electronic LC2N plug and it gives me the correct spec in seconds!
Yes Those newer standards are significant improvement for lot of workflows. And compared to analog/digital transition period and mess with different standards it's a goodsend.

Michal
Old 8th May 2019
  #9
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Quote:
Originally Posted by tedmanzie View Post
Ok I installed the PSP Triple Meters - it gives a more steady reading compared to the mvMeters, which makes the PSP much easier to use.

However, the default ref level of Triple Meters is -12dBFS (4PPM), but the ref level of mvMeters is -18dBFS (4PPM).

I adjusted the ref level of the Triple Meters to -18, but it's a bit weird that the default is -12 isn't it? I would expect the default to be the standard.
Yes you're right, sorry I forgot to mention that, I set it immediately after first open. The reference has to be at -18 dBFS.
I'm not sure, why -12 is their default (maybe some overlook, it doesn't resemble any broadcast standard to me), but when it's set to -18, it should give you right readouts.

Michal
Old 8th May 2019
  #10
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Thomas W. Bethe's Avatar
 

Verified Member
To the OP,

If you go to any American radio station and look at the VU meters most times they are pegged. The same, I assume, with European radio stations. Meters are suppose to be like speedometers but like a lot of drivers no one looks at their speedometer they just "wing it". Levels and specs are different all over the world. I guess you just have to meet the ones that the festival organizers have spec'd. Best of luck!
Old 13th May 2019
  #11
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Hi Ted,

I have some good news, because TB Pro Audio released new version of mvMeter2 today . There is updated PPM meter mode with fixed ballistics and over indicator.
I tested it myself quite thoroughly according to IEC standard before its release.
AFAIK it's only freeware British style PPM meter available for all common plugin formats. Kudos to TB Pro Audio .

Michal
Old 13th May 2019
  #12
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Quote:
Originally Posted by msmucr View Post
Hi Ted,

I have some good news, because TB Pro Audio released new version of mvMeter2 today . There is updated PPM meter mode with fixed ballistics and over indicator.
I tested it myself quite thoroughly according to IEC standard before its release.
AFAIK it's only freeware British style PPM meter available for all common plugin formats. Kudos to TB Pro Audio .

Michal
Great news! Thanks Michal, and TB Pr Audio!
Will install today.
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