ProTools HD - Hardware I/O latency
Old 13th March 2008
  #1
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ProTools HD - Hardware I/O latency

I'm fairly new to pro tools hd and I have a question. I have bunch of outboard gear that I'm trying to use as inserts or as a send returning to aux channel. The question is: what about the latency of harware compressors/ eqs etc? Even with delay compensation enabled I still hear some latency. There is a way to enter latency compensation values in I/O setup window but how do you calculate that value? I'm using a lot of parallel compression using external gear and this bothers me a bit.

Thx,

Chris
Old 13th March 2008
  #2
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Zep Dude's Avatar
 

If you do a send returning to a different aux channel PT latency compensation won't work. You have to do this as an insert. If you have 192 interface the hardware latency comp is already set up, otherwise you can manually enter values either per track or in the IO window per channel. To figure out your DA-AD latency play a track through the DA-AD loop and record it back. compare the waveform of the new track to the original and that will tell you the latency delay. However, with some converters, like apogee they have less latency than the 192's so you have to enter the offset value for each individual track -see their website. You should read the manual on this. It's important to understand how this all works to keep your tracks in correct phase with each other. "Automatic" Delay Comp is not really so automatic.

Also, some plugins, like the MDW don't report correct values to delay comp -its off by 1 sample so you'll hear phase issues with parallel tracks. I've heard some of the Waves have this issue as well.

Any latency your analog gear has is only measurable in the nanoseconds -way less than 1 sample.
Old 13th March 2008
  #3
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Quote:
Originally Posted by Zep Dude View Post
If you do a send returning to a different aux channel PT latency compensation won't work. You have to do this as an insert. If you have 192 interface the hardware latency comp is already set up, otherwise you can manually enter values either per track or in the IO window per channel. To figure out your DA-AD latency play a track through the DA-AD loop and record it back. compare the waveform of the new track to the original and that will tell you the latency delay. However, with some converters, like apogee they have less latency than the 192's so you have to enter the offset value for each individual track -see their website. You should read the manual on this. It's important to understand how this all works to keep your tracks in correct phase with each other. "Automatic" Delay Comp is not really so automatic.

Also, some plugins, like the MDW don't report correct values to delay comp -its off by 1 sample so you'll hear phase issues with parallel tracks. I've heard some of the Waves have this issue as well.

Any latency your analog gear has is only measurable in the nanoseconds -way less than 1 sample.
Zep Dude! Thank you so much for this quick answer. I'm using SSL Alpha Link / Delta Link converters so I have to do the recording test to figure out the latency. You say that if I return to separate aux channel then the digi delay compensation won't work, right? But since there is virtually no latency on the hardware side then the only latency is on the converter side, right? So if I enter proper latency values in all I/O fields (should be the same number for all 24 I/0 , right?) then it should not matter to which channel I return the signal. Are those manually entered values part of automatic delay compensation or not? According to logic they should not be. Am I right?

chris
Old 13th March 2008
  #4
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dubrichie's Avatar
well, since the SSL Alpha Link / Delta Link have to go through TWO boxes before they reach the ADDA and the correlating i/o channels are not recognised by PT, yes, you will have to adjust the latency manually.

easiest way is to send a transient audio "ping" signal through the i/o (DA/AD) that you want to insert/send/return on and then use this "spike" in the waveform to visually calculate the exact delay in samples, having zoomed in on the waveforms.
Old 13th March 2008
  #5
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Thread Starter
Thanks Richie! Will it work OK in the "send-aux" scenario as well? I hope I don't have to manually check all the files all the time!

thx,

chris
Old 14th March 2008
  #6
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dubrichie's Avatar
yes, it should.

once you specify the i/o path (ie which output and which input to be used for the send and aux respectively) this method should work just fine and you should only have to do it once.

however, i may be wrong and am willing and able for a healthy correction!
Old 14th March 2008
  #7
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lozion's Avatar
 

not to hi-jack or anything but what about converters going in lightpipe to the 192/96?
Are they automatically compensated for in the same manner as the ad/da of the digi boxes? And to push the question further, what about converters going in lightpipe thru an adat bridge via the legacy port? Mmm
Old 14th March 2008
  #8
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dubrichie's Avatar
Quote:
Originally Posted by lozion View Post
not to hi-jack or anything but what about converters going in lightpipe to the 192/96?
Are they automatically compensated for in the same manner as the ad/da of the digi boxes? And to push the question further, what about converters going in lightpipe thru an adat bridge via the legacy port? Mmm
i don't think so, as PT has no way of "knowing" what the latency of the other converters connected via lightpipe is.

again, you will have to "ping" them and manually enter the values in samples.
Old 14th March 2008
  #9
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lozion's Avatar
 

Quote:
Originally Posted by dubrichie View Post
i don't think so, as PT has no way of "knowing" what the latency of the other converters connected via lightpipe is.

again, you will have to "ping" them and manually enter the values in samples.

Well, stangely enough, there is compensation happenning on those lightpipe channels, suggesting PT does ping itself to apply proper correction... Maybe because those i/o's ARE running through a DIGI box, as opposed to 3rd party interfaces where manual compensation needs to be applied?
Old 16th March 2008
  #10
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mmm?
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