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Inputlevel for live broadcast mix
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baldrian
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31st May 2012
Old 31st May 2012
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Inputlevel for live broadcast mix

Hello,

I have the following question. Most live mixes i do are either for live broadcast or kind of live on tape. It is mostly sportsevents or conferences. Usually a peaklevel of -9 dB FS is requested. A Commentator or anchor is present most of the time and so far i set my levels that these signals get close to -9 dB FS. I know a lot of people recommend to go into the desk around -18 dB FS. And i would appreciate 9 more dB of headroom... But how do you get your final mix 9 dB louder? Digital trim on every input, or just on the outputs? Setting the faders to +9 instead of unity is a kind of semiperfect approach.
I couldn't figure out a workflow so far that is really working for me.
BTW I always ask myself the same question in the studio while recording VO, but there i'm not half as worried about clipping as in a live situation...

Looking forward to hear some ideas from you guys...
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31st May 2012
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I also do a lot of live broadcast. There, my friend is the VU meter. We peak spoken word at around -5VU.

So it's not your average level that sits at -9 dBFS, but your peak level isn't it?

Basically you are limited to what the compressor in the TELOS does, or if you are making a broadcast from your studio, just use a complimiter to control your dynamic range. Also not a bad idea for on location as well. We use the dbx 160. It is a basic complimiter that works well in all situations.

When making a live broadcast, I always set my levels from a genuine VU meter, not from a digital meter. Also I adjust level while listening to the air signal returned from an actual FM tuner. We have a button for that on the console.
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31st May 2012
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Where are you working? If you are quoting a 'peak' level of -9dBfs, I suspect it is Europe (EBU rules). In which case the levels are reference (line up on reference tone, elsewhere called 0VU) -18dBfs, peak level -9dBfs and clip level 0dBfs. The space between -9dBfs and 0 is 'goof room' - important in live broadcast, where occasional/accidental signals peaking over -9dBfs ddon't get distorted and they can be absorbed by the downstream limiter.

(Except in lands where VU meters are common, the levels tend to be -20dBfs reference, -10dBfs peak and 0dBfs clip.)

Ask the broadcaster. It's mainly important that their meters and yours are lined up to read the same.
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31st May 2012
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Download the ATSC A/85 doc. Sample level files for meeting the CALM act legal requirement of -24 LKFS are in there. 0 VU average, not peaking beyond +2-3 VU, will get you there, as Plush says. If you don't have a VU or similar loudness meter, you need one to do this properly.

https://www.google.com/search?rlz=1C...&q=atsc+a%2F85
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31st May 2012
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Quote:
Originally Posted by brew View Post
Download the ATSC A/85 doc. Sample level files for meeting the CALM act legal requirement of -24 LKFS are in there. 0 VU average, not peaking beyond +2-3 VU, will get you there, as Plush says. If you don't have a VU or similar loudness meter, you need one to do this properly.

https://www.google.com/search?rlz=1C...&q=atsc+a%2F85
That is only relevant for the united states, we still need to know where and for what medium the op is mixing.
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1st June 2012
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Quote:
Originally Posted by huub View Post
That is only relevant for the united states, we still need to know where and for what medium the op is mixing.
In this case, we do not need to sweat the details. For Europe, replace the K with a U. Otherwise the standards are basically the same. If you mix for ATSC, you will be in compliance with Europe as well. See R 128. Calling these two things different is splitting hairs. If you mix to either of these guidelines, you'll have a good mix, regardless of the medium. To make your good mix medium-specific, add a limiter to taste.
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1st June 2012
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Thanks for your input so far.
I think i have to specify my question. It's not about being confused about delivery specs, i know thats a whole different story.
I want to know if any of you uses digital gain/trim on either the inputchannels or the outputbusses when using a digital desk, to preserve more headroom for the a/d conversion. I thought digital mixer usually works with a higher internal bit depth than its a/d conversion. So if I try to keep my inputs peaking around -18 dB FS and apply a +9 dB via digital trim, even if a signal goes over 0 dB FS internally, a limiter on the outputbuss could lower the signal to a point under 0 dB FS.

Maybe i got something wrong here, just remembered that i can clip a channel in Pro Tools, lower the masterfader and i still have an undistorted output. I guess i should just try it, but couldn't resist to ask if anybody is doing this or can tell me why it is a stupid idea ;-)
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1st June 2012
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Quote:
Originally Posted by brew View Post
In this case, we do not need to sweat the details. For Europe, replace the K with a U. Otherwise the standards are basically the same. If you mix for ATSC, you will be in compliance with Europe as well. See R 128. Calling these two things different is splitting hairs. If you mix to either of these guidelines, you'll have a good mix, regardless of the medium. To make your good mix medium-specific, add a limiter to taste.
Not really, as not all countries have officially adopted R128, some still have "old-fashioned" -9dBFs peak.

Anyway, as the OP has specified his question; Before R128, and still actually, I used to leave some healthy headroom on individual input channels (peak around -10 dBFs generally) Even without limiter (but with compressors where needed, such as on spoken word) I had a mix that was fairly broadcast ready, levelwise..
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1st June 2012
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It would be like a joke to clip any channel or any part of the console. No reason to do it especially in broadcast where conservative levels are the watchword.

Getting console gain staging correct is the first requirement. Hitting a certain output level is so easy.
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1st June 2012
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Quote:
Originally Posted by baldrian View Post
I want to know if any of you use digital gain/trim on either the input channels or the output busses when using a digital desk, to preserve more headroom for the a/d conversion.
I see what you mean. It's not a bad idea as long as you don't get carried away. My approach is to try to get the levels right at the A/D analog stage. If you are trimming more than +/- 8 dB, to me that implies you have a signal level problem that should be addressed elsewhere. Having gains all over the place doesn't sit right to me.

When your output target is 0 VU or -24 LKFS, you don't really need to worry about clipping, because you have 20 dB headroom in a SMPTE system. This is why using a calibrated monitor gain and 0 VU is such a good idea--it leaves you to focus on the mix and not the technical parameters.
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