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Pros/cons of look ahead
Old 11th May 2006
  #1
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Pros/cons of look ahead

What exactly does the look ahead function of digital limters do.

Is it a good or sometimes negative thing.


Cheers
Old 11th May 2006
  #2
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A look ahead limiter allows for a perfect "brick wall" to be achieve in limiting. If you can look ahead in the signal, the limiter can anticipate loud peaks before they occur and lower the volume before they arrive, so that the audio never exceeds the threshold. This is also sometimes refered to as a negative attack time.

As far as I know this is the only benefit. For digital formats, it's pretty important to never exceed 0dBFS, explaining why look ahead limiters are so popular in mastering.

Maybe someone like Mr. Katz can chime in to better explain the pros and cons of this type of limiting.
Old 11th May 2006
  #3
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Quote:
Originally Posted by pingu
What exactly does the look ahead function of digital limters do.

Is it a good or sometimes negative thing.
It allows a zero attack time by delaying the input relative to the side chain so you can "see the peak coming."

Rarely used in anything but brick-wall limiters. Was either a breakthrough or an ear-breaker, depending on how you look at it....

DC
Old 11th May 2006
  #4
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Thanks guys.



So if a limiter has the option to select look ahead, is it a good idea to do so?

Is there a down side?
Old 13th May 2006
  #5
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Quote:
Originally Posted by pingu
Thanks guys.



So if a limiter has the option to select look ahead, is it a good idea to do so?

Is there a down side?
Not being able to decide for yourself, I guess....

DC
Old 13th May 2006
  #6
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Quote:
Originally Posted by dcollins
Not being able to decide for yourself, I guess....

DC
Now That's ****in' funny.
Old 13th May 2006
  #7
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Thanks guys.



You mongrels.



I love DC
Old 13th May 2006
  #8
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There's actually an argument for not using look-ahead having to do with the character of the distortion that's generated.
Old 13th May 2006
  #9
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Quote:
Originally Posted by Bob Olhsson
There's actually an argument for not using look-ahead having to do with the character of the distortion that's generated.

Thats what i was chasing.


Cheers
Old 13th May 2006
  #10
Mastering
 

Quote:
Originally Posted by DeeDrive
A look ahead limiter allows for a perfect "brick wall" to be achieve in limiting. If you can look ahead in the signal, the limiter can anticipate loud peaks before they occur and lower the volume before they arrive, so that the audio never exceeds the threshold. This is also sometimes refered to as a negative attack time.

As far as I know this is the only benefit. For digital formats, it's pretty important to never exceed 0dBFS, explaining why look ahead limiters are so popular in mastering.

Maybe someone like Mr. Katz can chime in to better explain the pros and cons of this type of limiting.
Or anyone else who knows the answer! Here's my point of view: Look-ahead is EXTREMELY important in digital limiting where you must catch peaks even as short as a sample. Lookahead is available in compressors as well as limiters but much less important. Basically, with compression, the true attack time cannot be shorter than the lookahead. For example, if you look ahead by 10 ms, then any transients shorter than 10 ms will be caught. But if you're like me, and tend to use much longer attack times with compressors, lookahead is probably an academic argument, and your 1 or 10 or whatever millisecond lookahead is probably meaningless if you are running a much longer attack time. But if you want a true 5 ms attack time, you better have a lookahead that's 5 to 10 ms.

However, when I'm doing parallel compression with a very fast attack time, I have to use a parallel compressor with a lookahead of at least 10 ms. Otherwise the transients will be stomped on. So lookahead is very important if you are using a parallel compression technique to try to preserve transients.
Old 13th May 2006
  #11
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Quote:
Originally Posted by bob katz
Or anyone else who knows the answer! Here's my point of view: Look-ahead is EXTREMELY important in digital limiting where you must catch peaks even as short as a sample. Lookahead is available in compressors as well as limiters but much less important. Basically, with compression, the true attack time cannot be shorter than the lookahead. For example, if you look ahead by 10 ms, then any transients shorter than 10 ms will be caught. But if you're like me, and tend to use much longer attack times with compressors, lookahead is probably an academic argument, and your 1 or 10 or whatever millisecond lookahead is probably meaningless if you are running a much longer attack time. But if you want a true 5 ms attack time, you better have a lookahead that's 5 to 10 ms.

However, when I'm doing parallel compression with a very fast attack time, I have to use a parallel compressor with a lookahead of at least 10 ms. Otherwise the transients will be stomped on. So lookahead is very important if you are using a parallel compression technique to try to preserve transients.


Thanks a lot Bob.
Old 13th May 2006
  #12
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e-cue's Avatar
 

Quote:
Originally Posted by pingu
Is there a down side?
On some devices or plug in's- increased latency.
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