Headroom in digital audio

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Re: Headroom in digital audio

Postby Malcolm Boyce » Mon Jan 09, 2012 1:06 pm

Mathieu Benoit wrote:
Malcolm Boyce wrote:Sonar does show levels above zero as well. It is handy, and I wouldn't love not having it.


It's really a non-issue for me since I don't make it a habit of having levels anywhere near there.
You've never had a master or mix bus hit zero?
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Re: Headroom in digital audio

Postby macrae11 » Mon Jan 09, 2012 1:13 pm

Malcolm Boyce wrote:As Andrew already mentioned, I remember being less than thrilled with the metering in ProTools compared to Sonar.


Do you happen to recall specifically what the problem was? I'm just wondering if it's an old version thing that's been improved, or if there's something I'm missing that I don't even know I'm missing.
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Re: Headroom in digital audio

Postby Malcolm Boyce » Mon Jan 09, 2012 1:18 pm

macrae11 wrote:
Malcolm Boyce wrote:As Andrew already mentioned, I remember being less than thrilled with the metering in ProTools compared to Sonar.


Do you happen to recall specifically what the problem was? I'm just wondering if it's an old version thing that's been improved, or if there's something I'm missing that I don't even know I'm missing.
No, I don't remember. It has been a while since I've had to be in front of ProTools for anything of consequence so it may be different now. There's a good chance there's a thread in here about what I was looking at. :-)
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Re: Headroom in digital audio

Postby Mathieu Benoit » Mon Jan 09, 2012 1:23 pm

Malcolm Boyce wrote:
Mathieu Benoit wrote:
Malcolm Boyce wrote:Sonar does show levels above zero as well. It is handy, and I wouldn't love not having it.


It's really a non-issue for me since I don't make it a habit of having levels anywhere near there.
You've never had a master or mix bus hit zero?


Sure it happens, and then I correct it and move on. 0 dbfs for me is the ceiling I don't really care how far above the ceiling I am at. If I'm hitting 0 dbfs I have a problem that I need to fix, and knowing that it's at 3.45 over 0 isn't that relavent to me. But again usually it's not even on my radar. If it comes up I address what went wrong in my gain staging, I don't start wondering how far over 0 I went.

So I guess my question to you is, how does that feature serve you in your workflow?
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Re: Headroom in digital audio

Postby Malcolm Boyce » Mon Jan 09, 2012 1:34 pm

Mathieu Benoit wrote:So I guess my question to you is, how does that feature serve you in your workflow?
Simply knowing how far over I am, VS having to trial and error lowering levels until I'm below 0 again. If I know after running a pass of a mix that something peaked at +2.4 on the mix buss, not only can I quickly adjust for that, but I can find that peak point and see/hear what it was. Knowing how far "over" you are is extremely helpful.

I know we're all working in this new era of everyone talking about keeping levels lower, and that is most certainly true on input, but let's not make on that a lot mixes aren't still using only the top 6 dB on the scale.
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Re: Headroom in digital audio

Postby Mathieu Benoit » Mon Jan 09, 2012 2:11 pm

Malcolm Boyce wrote:Simply knowing how far over I am, VS having to trial and error lowering levels until I'm below 0 again. If I know after running a pass of a mix that something peaked at +2.4 on the mix buss, not only can I quickly adjust for that, but I can find that peak point and see/hear what it was. Knowing how far "over" you are is extremely helpful.

I swear I'm not trying to be difficult here but I don't understand your logic. I can find peak points at 0 too and quickly adjust for that. I don't need to know how far over the line, simply reaching the line is enough to know I need to make some adjustments. If I'm missing something, then please enlighten me. I'm a long way from knowing everything... but I'm certainly at the point where I question everything. ;-)

Malcolm Boyce wrote:... but let's not make on that a lot mixes aren't still using only the top 6 dB on the scale.


That's pretty much back to full circle. I try to keep my mixes around -12dbfs and I asked you guys what you did since I've never had a discussion with anyone else about it before. Andrew gave his input and said how his sessions tend to be. If your mixes are only using the top 6dB on the scale then by all means, say so because I'd love to discuss what different people are doing to see what I can stand to learn from that.
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Re: Headroom in digital audio

Postby Malcolm Boyce » Mon Jan 09, 2012 2:29 pm

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Re: Headroom in digital audio

Postby Mathieu Benoit » Mon Jan 09, 2012 2:40 pm

Malcolm Boyce wrote:Blast from the past:

viewtopic.php?f=2&t=145&hilit=protools+meters


I see your blast from the past and I raise you my blast from the present:

http://forums.middleaudio.com/viewtopic.php?p=15084#p15084

By the way when the Pro tools mixer is not in narrow view the dbfs scale is on the right and the fader level scale. as per the image that Andrew posted a link to earlier in this thread:

http://forums.middleaudio.com/viewtopic.php?p=15105#p15105
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Re: Headroom in digital audio

Postby macrae11 » Mon Jan 09, 2012 2:49 pm

Mathieu Benoit wrote:
Malcolm Boyce wrote:Blast from the past:

viewtopic.php?f=2&t=145&hilit=protools+meters


I see your blast from the past and I raise you my blast from the present:

http://forums.middleaudio.com/viewtopic.php?p=15084#p15084

By the way when the Pro tools mixer is not in narrow view the dbfs scale is on the right and the fader level scale. as per the image that Andrew posted a link to earlier in this thread:

http://forums.middleaudio.com/viewtopic.php?p=15105#p15105

Correct Matt, but at the time Mal posted the original thread, Pro Tools did not display it's meters this way. It was corrected I believe in v7 or 8.
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Re: Headroom in digital audio

Postby Mathieu Benoit » Mon Jan 09, 2012 3:02 pm

macrae11 wrote:Correct Matt, but at the time Mal posted the original thread, Pro Tools did not display it's meters this way. It was corrected I believe in v7 or 8.

..and at THIS time his argument is moot. I love this thread by the way. Best thread so far this year.
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Re: Headroom in digital audio

Postby Christian LeBlanc » Mon Jan 09, 2012 3:10 pm

This thread accidentally taught me how to easily automate volume and panning in my old version of Cubase when I was looking up how to do something else, so...agreed.
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Re: Headroom in digital audio

Postby Mathieu Benoit » Mon Jan 09, 2012 9:47 pm

Christian LeBlanc wrote:This thread accidentally taught me how to easily automate volume and panning in my old version of Cubase when I was looking up how to do something else, so...agreed.


Hopefully this thread has taught you more than that. There's a nice little trove of information here.
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Re: Headroom in digital audio

Postby Christian LeBlanc » Tue Jan 10, 2012 10:51 am

Mathieu Benoit wrote:Hopefully this thread has taught you more than that.

Oh yeah, that was just bonus learnin' over and above the research I did before I commented, and the thread itself. Given that people are still sending files to be mixed that are peaking at 0 dbfs, the topic itself seems like a well-kept secret. I think I'd like to record some demo tracks sometime with this in mind, one recorded the way I would have before this thread, and one after, just to see what happens.
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Re: Headroom in digital audio

Postby Mathieu Benoit » Tue Jan 10, 2012 11:05 am

Christian LeBlanc wrote: I think I'd like to record some demo tracks sometime with this in mind, one recorded the way I would have before this thread, and one after, just to see what happens.


What will happen is that you can spend your energy mixing and not worrying about headroom, not to mention the potential you create for clipping on the way in. I easily mix twice as fast as I did when I started mixing and everything was pinned everywhere. When headroom is a huge issue in mixing you spend more time doing damage control that you do trying to make a musical statement. So if you get to the point where everything is getting out of hand, you're probably better served to start from scratch and bring everything way down and then try to not mix yourself into a corner again. With DAWs it's really simply to just hit "reset" and give yourself another chance so long as you weren't clipping on the way in and you weren't doing anything destructive (non-reversable) in the box.

EDIT: If you did do something non-reversable, then better luck next time!
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Re: Headroom in digital audio

Postby macrae11 » Tue Jan 10, 2012 11:30 am

Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble. Even if you're bussing to a stereo track, or sending out to a piece of hardware you can create a master fader for that bus and it will do the same thing. There might be 1 or 2 mixes a year where I have to do that because I'm not paying attention. Certainly not the right way to do things, but it can be a life saver instead of trying to go back and salvage your mix.
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Re: Headroom in digital audio

Postby Mathieu Benoit » Tue Jan 10, 2012 11:46 am

macrae11 wrote:Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble. Even if you're bussing to a stereo track, or sending out to a piece of hardware you can create a master fader for that bus and it will do the same thing. There might be 1 or 2 mixes a year where I have to do that because I'm not paying attention. Certainly not the right way to do things, but it can be a life saver instead of trying to go back and salvage your mix.


I did know that because we've discussed it before but it's good to mention for clarification. To be honest though, if I run into headroom issues it's usually in the drum buss. Maybe because I'm a drummer? :oops: So when you say bussing to a stereo track... I assume you meant that aux busses work the same way? I always thought they did but I never actually asked you.

EDIT: Christian (or anyone else paying attention)... Is it clear when we talk about 24 bit, 32 bit float, and 48 bit...etc? I don't want to presume that everyone understands what that is refering to, since I certainly didn't when I started.
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Re: Headroom in digital audio

Postby Christian LeBlanc » Tue Jan 10, 2012 12:13 pm

I think of it in terms of image resolution - like 16-bit will look as good as 48-bit in a thumbnail, but if you want to blow it up to poster-size, 16-bit is going to have lots of blocky artifacts and visual noise that you wouldn't otherwise notice. 24-bit is going to look a lot cleaner, though. The higher the number, the more "room" you have to tweak and make changes to your sounds without mucking things up too bad, which is why people will associate a higher bit rate with more headroom.

I also have a working understanding that a mix-down file will sound better in 24-bit if you were working in 32-bit, even though the song itself is only 24-bit.

What I understand of float, is that it's like a floating-point decimal, keeping high resolutions on what you're working in...when you mix down to a cd-quality file, you won't hear the 32-bit float quality, but you'll hear a difference than if you were working in 16-bit to begin with. Is everything above 24-bit automatically float?
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Re: Headroom in digital audio

Postby Malcolm Boyce » Tue Jan 10, 2012 12:58 pm

macrae11 wrote:Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble.
Is there a trim or input level coming into the master fader as well, or just the fader itself? In Sonar on a buss there is "Input Gain" control at the top which is handy if you are processing on the mix and want to control the overall level of what's coming in as opposed to the output of the buss.
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Re: Headroom in digital audio

Postby macrae11 » Tue Jan 10, 2012 1:03 pm

Mathieu Benoit wrote:
macrae11 wrote:Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble. Even if you're bussing to a stereo track, or sending out to a piece of hardware you can create a master fader for that bus and it will do the same thing. There might be 1 or 2 mixes a year where I have to do that because I'm not paying attention. Certainly not the right way to do things, but it can be a life saver instead of trying to go back and salvage your mix.


I did know that because we've discussed it before but it's good to mention for clarification. To be honest though, if I run into headroom issues it's usually in the drum buss. Maybe because I'm a drummer? :oops: So when you say bussing to a stereo track... I assume you meant that aux busses work the same way? I always thought they did but I never actually asked you.


Aux tracks are different because the audio signal is prefader, which is the same as all audio tracks. With a master fader the signal is post fader so you can literally pull the signal down going INTO the track, which is why you can eliminate headroom issues. With the drum track issue you would have to create a master fader and assign it to the bus you're using for your drum sub.

You can use this same technique if you are routing a mixdown to an internal PT track for printing and you want to add processing to the 2bus. Instead of routing into an aux track, applying your processing, then routing out of the aux into your audio track, you can simply route directly to your audio track and create a master fader assigned to the bus. Same amount of tracks, but quicker to set up and more control.

All that being said, I would never go to this much trouble for a drum sub headroom issue. Usually drum sub routing is a bit simpler than a full mix(though not always) so I'll just bring all the faders down. The way I do this is with a VCA track assigned to the drum group. This way I have full control of levels both going into my drum sub and it's processing(VCA) and overall drum sub level post processing(drum sub AUX).
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Re: Headroom in digital audio

Postby macrae11 » Tue Jan 10, 2012 1:04 pm

Malcolm Boyce wrote:
macrae11 wrote:Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble.
Is there a trim or input level coming into the master fader as well, or just the fader itself? In Sonar on a buss there is "Input Gain" control at the top which is handy if you are processing on the mix and want to control the overall level of what's coming in as opposed to the output of the buss.

I explained this in the above post, the master fader is always pre fader, pre insert. There's no dedicating input trim on individual tracks.
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Re: Headroom in digital audio

Postby macrae11 » Tue Jan 10, 2012 1:15 pm

Christian LeBlanc wrote:I think of it in terms of image resolution - like 16-bit will look as good as 48-bit in a thumbnail, but if you want to blow it up to poster-size, 16-bit is going to have lots of blocky artifacts and visual noise that you wouldn't otherwise notice. 24-bit is going to look a lot cleaner, though. The higher the number, the more "room" you have to tweak and make changes to your sounds without mucking things up too bad, which is why people will associate a higher bit rate with more headroom.

I also have a working understanding that a mix-down file will sound better in 24-bit if you were working in 32-bit, even though the song itself is only 24-bit.

What I understand of float, is that it's like a floating-point decimal, keeping high resolutions on what you're working in...when you mix down to a cd-quality file, you won't hear the 32-bit float quality, but you'll hear a difference than if you were working in 16-bit to begin with. Is everything above 24-bit automatically float?


You've sort of got it, but the picture analogies are throwing you off. First of all bit depth refers to dynamic range, not "quality", or resolution. Since all digital files have the same max level of 0dBFS, you don't actually gain any headroom when increasing bit depth, you actually gain footroom. But since we have more footroom before the noise floor, we can record at a lower level, thereby allowing ourselves more headroom, which is what this conversation is all about. 24 bit actually has 144dB of dynamic range which is approximately the range from dead silence to making your eardrums meet in the middle of your head. ie Way more than you need. But this allows us lots of freedom with levels, as long as we stay clear of 0.

Another misconception is that 32 bit will sound better than 24 bit which is totally false. 32 bit files are capable of a much greater dynamic range, but as stated 24 bit has more than enough dynamic range for humans, so as long as you maintain good gain structure and stay within that range there will be no difference between the 24 bit and 32 bit float files. If you do stray outside that range in 32 bit float, when you reduce down to 24 bit, you will be in for a world of hurt. 32 bit float files are actually just 24 bit files with an 8 bit modifier to fake their extended dynamic range. So basically you still only have 144 dB of dynamic range, but that range can be from 0-144, or 96-240, 144-288, or 576,254-576,398.

Everything above 24 bit is not float, for instance Pro Tools HD has a 48 bit fixed internal mixer, so it has a true dynamic range of 288dB, which is only useful when we starting getting into the math of signal processing, which I'm am woefully unprepared to discuss at any length. All of this is before we start talking about dither too, which is a whole nother kettle o' fish.
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Re: Headroom in digital audio

Postby Christian LeBlanc » Tue Jan 10, 2012 1:24 pm

Thanks for taking the time to explain that - I like having this info stored in this thread, instead of spread across 4 or 5 different websites I saw that I'll probably never find again.
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Re: Headroom in digital audio

Postby Malcolm Boyce » Tue Jan 10, 2012 1:25 pm

macrae11 wrote:
Malcolm Boyce wrote:
macrae11 wrote:Just so you know Matt(and everyone) Pro Tools master faders are all 48 bit (or 32 bit float for LE) so if you do get into trouble all you have to do is lower the master fader to get yourself out of trouble.
Is there a trim or input level coming into the master fader as well, or just the fader itself? In Sonar on a buss there is "Input Gain" control at the top which is handy if you are processing on the mix and want to control the overall level of what's coming in as opposed to the output of the buss.

I explained this in the above post, the master fader is always pre fader, pre insert. There's no dedicating input trim on individual tracks.
The "Master" fader is the input... Interesting. Just a different way of looking at it.

This is truly one of the best things in Sonar is the flexibility in routing. There is no difference between any of the busses or groups or auxes... and any of their main outs are assignable to any physical hardware output.

This reminds me of the different ways of dealing with masters on digital live consoles. Some desks have dedicated "stereo" masters, and some you make whatever one you want to be it... or none.

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Re: Headroom in digital audio

Postby Mathieu Benoit » Tue Jan 10, 2012 1:42 pm

macrae11 wrote:All that being said, I would never go to this much trouble for a drum sub headroom issue. Usually drum sub routing is a bit simpler than a full mix(though not always) so I'll just bring all the faders down. The way I do this is with a VCA track assigned to the drum group. This way I have full control of levels both going into my drum sub and it's processing(VCA) and overall drum sub level post processing(drum sub AUX).


Ah VCA tracks... Right. Forgot about that, I've yet to use them. I simply bring down the faders of the channels in that subgroup for now if I need to.
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Re: Headroom in digital audio

Postby macrae11 » Tue Jan 10, 2012 1:47 pm

Malcolm Boyce wrote:This is truly one of the best things in Sonar is the flexibility in routing. There is no difference between any of the busses or groups or auxes... and any of their main outs are assignable to any physical hardware output.

Pro Tools is the same way, it just has tracks/channels with different functions, but the routing is the same in all tracks and can go anywhere. In fact they're all just called buses, Matt and I are just referring to them by their function as opposed to what they are.
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