Proper audio levels for Bars and Tone

[Jeff Carpenter]

You can think of digital audio exactly like you did analog. The only difference is that what you usd to call “0” you now call… “?”

That’s the confusing part. “?” can really be any number from -24 to -6. Take your pick! It’s all up to you or your clients.

But for the sake of example, lets pick -12. That’s a reasonable choice. Having decided on -12 as your “new 0” here’s what you’d do:

In editing you’d be trying to keep most sounds in the -16 to -12 range. Quiet sounds can go lower, of course, and loud sounds can go up to -6 if you really need to. I wouldn’t let anything go higher than that.

Then, when going back to tape, set your tone to -12 and you’re good to go. If anyone makes an analog dub of this program and sets the tone to “0” they’ll find most of your program comes right up to “0” and that it sometimes goes over just a little. In other words, it should dub just fine.

That’s really all you need to know about how to make it work. But what about other numbers? Why pick something other than -12? Well, if you were mixing a live TV show that might be a little too close to the dreaded digital-zero on the top of the scale. In a TV studio they might set tone at -18 and try to stick tot that. THEIR “loud” peaks would only go up to -12, giving them bit more room to be safe. Since you’re editing ou don’t need that safety zone so you might pick -12. Or something in between.

Picking what level to master at can change, but the general idea never does: Pick a number and then treat that number as “analog zero” for the rest of your project.

[Jerrold Le tourneau]

I set my levels as you have suggested in practice. What is causing me grief is that I am making video dubs from tapes that come from a couple different post houses and the BAR and Tone are substanially lower 12db to 18db that the program material. When I make a dubs from them I have to set the audio level for bars and Tone at -12db so that the program audio does not peak beyond 0 on the decks VU meters. I always thought the prupose of Bars and Tone was to set the MAXIMUM audio level. When I master my tapes I always leave at least 6db headroom and don’t peg my audio levels into the red on the decks.

For the record I use a Sony UVW-1800 and a JVC BRS-800U S-VHS deck for dubs.

[Jeff Carpenter]

When dubbing from Digital to Analog, play the tone on the digital tape and set the analog deck to “0”

When dubbing from Analog to Diital, play the tone on the analog tape and set the digital deck to “-12”

The probem with the tapes you’re getting from the dub houses…I’m not fully understanding it but it sounds like THEY’RE doing something wrong. The whole point of tone is that it should make everything rigth once you calibrate it…it sounds like their tone and their program doesn’t match which means that isn’t something you’re doing wrong.

[Jerrold Le tourneau]

Your levels recipe is exactly what I employ now. Just confirms my thought that the dub house is setting thier Bars and Tone levels for a Digital dub and not an analog copy. That would explain the Bars being 12db lower than the program material. I’m just programmed to see Bars and Tone on an analog system at 0db so this screws me up especiialy when I have to turn around and make dub copies from the production house provided tapes. I keep having to adjust the levels between the Bars and Tone and the program material to keep everything in line.

I duplicate tape master copies coming from an in-house FCP system and out-sourced production houses that are sent to various media outlets for inclusion into news features. So, I try to be aware of audio and video levels so that nothing is bounced back.

[Chris Borjis]

bars and tone on a uv meter that register zero
(the first red line on a betacam uv-1800 deck)

Read as -20 on a digital betacam.

Everything thats ever come in here from New York to Hollywood has been this way.

Though occasionally we get odd tones that are not anywhere close to being helpful in which case I set things manually, not to exceed -10 on average with an absolute ceiling of -6.

my 002 cents

[Gary Hughes]

Borjis,

You are exactly correct and I have used that exact levels setup for years, sending tapes to broadcast and cable, all over the nation. However, now that I have a DV-Cam deck, -12db instead of -20db seems to be the logical choice. I have been making my DV-Cam masters at -12dB and my digibeta masters at -20dB ever since, and still no complaints from broadcast or cable.

On my digibeta, -20dB is reference. Nothing else makes sense. If you press the “fine adjust” button so that you can see fractions of a dB, it is based on -20dB. My DV-Cam deck doesn’t even have a marking on the meter for -20dB, though it does have one for -12dB. These are the only 2 standards I have ever seen used by anyone who is a serious pro.

Thanks,
Gary

[Michael Gissing]

Broadcast specs are simple. In SMPTE land tone on a digital machine is 1khz @ -20dbfs (db full scale). In the PAL world either -20 or -18dbfs is acceptable. Peak levels are then no more than 10db ABOVE that reference.

It is important to remember that professional digital machines have high gain analog outputs. If you use -12db tone and then had program levels peaking 10 db above that, then you would be sending high levels to any analog machine, running the risk of overloading the input circuits. That is why some digital machines let you trim the analog output level from professional +4db spec to 0db or even -10db domestic level specs.

Whilst it is important to realise that tone is just a line in the sand and totally irrelevent for digital to digital transfers, it does represent an important reference for analog dubbs. So best practice is to follow the broadcast spec. It is mandatory for most programs and should be considered the best standard for all work. I find it unusual that FCP defaults to -12db with its tone generator. But the golden rule is peak levels shall not exceed 10db above the reference.

[Jerry Hofmann]

What’s confusing you is the way you read digital meters as oppossed to analog. -12 works really well I think as you new house 0 as displayed on analog meters.

FCP has a set of analog meters btw… they are the Master outs in the Audio Mixer.

Jerry

[Rendertainmentllc]

I always set the tone in my timeline to be -20, as I’ll be outputting to either digi or HDCAM at -20. I never let my audio peak over -12.
It takes a little while to make the adjustment from analog to digital meters, but once you get used to the difference it’s no problem.