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  #1  
Old 08-16-2007, 10:23 PM
hef hef is offline
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Default Delay Compensation/Laybacks

okay, sorry in advance for the drawn out post. as i just finished reading a bunch of threads on here about delay compensation, i'm still a little confused.

I'm wondering how i should be using delay compensation while laying back to digibeta.
i've always done laybacks straight out from my Aux Stem tracks (Dia, Mus, Sfx) to digital tie lines to DigiBeta. In the past I never had to deal with print master tracks because i was delivering digibetas and d88s- no files. but now they want files and digibetas. when making files i see that they're slightly off which lead me to do some tests.

So i put a 2 pop on a dialog track in a heavily routed and lots of plugin session. I turned on Delay Comp and layed the pop back to digibeta 1&2 and then I turned off Delay Comp and layed the pop to 3&4.

then i made a new session and recorded the pop from digibeta back to 2 stereo tracks. the result was with delay compensation (1&2) the pop was 20 subframes early (why???) and without delay compensation (3&4) the pop was 20 subframes late.

my conclusion from this is that i've definitely been doing things wrong all along. and that to properly use delay compensation i should first record to a print master audio track, and then layback straight from that track to digi without delay compensation. does this make sense?

in any case i shouldn't be losing any sleep over 1/5 of a frame, but then again it is 1:15am and i'd like to really grasp this.
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  #2  
Old 08-17-2007, 03:28 AM
tom.joyce tom.joyce is offline
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Default Re: Delay Compensation/Laybacks


i have had a similar problem recently where i was using a BNR and having the delay compensation set on long. I was finding it was over compensating and was coming in 1 & 1/2frames early. This is now been fixed in cs3 although i still keep the compensation set to short.

tom
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  #3  
Old 08-17-2007, 05:47 AM
garret garret is offline
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Default Re: Delay Compensation/Laybacks

Hef,
If you are using Delay comp and then recording to a track you must control+apple+click on the delay comp box on the rec track in the mix window to disable protools from turning off delay comp for that track. This turns the writing blue. When you rec enable a track the Delay comp is disabled for that track that is why you are getting different readings. When you disable it then delay comp is always on, on that track so everything should line up correctly.
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Old 08-17-2007, 08:12 AM
hef hef is offline
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Default Re: Delay Compensation/Laybacks

Quote:
Hef,
If you are using Delay comp and then recording to a track you must control+apple+click on the delay comp box on the rec track in the mix window to disable protools from turning off delay comp for that track. This turns the writing blue. When you rec enable a track the Delay comp is disabled for that track that is why you are getting different readings. When you disable it then delay comp is always on, on that track so everything should line up correctly.
okay, but that doesn't expain when i'm laying back straight to digibeta and not printing to any track. when i recorded my 2 pop back in from digibeta i recorded it into a blank session with no delay compensation. so is it the case that you shouldn't go straight to digibeta from aux stem tracks. you should go to print master (w/ enabled Delay Comp) and then to digi??
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  #5  
Old 08-17-2007, 12:01 PM
garret garret is offline
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Default Re: Delay Compensation/Laybacks

Hef,
20 Subframes is pretty small. How far away is your digibeta machine? It could just be the delay for the round trip from protools to digi to protools. I know that when i record pips internally in protools with Delay comp on the print master and Stems are always bang on the money.
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  #6  
Old 08-18-2007, 09:41 AM
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Bob Brown Bob Brown is offline
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Default Re: Delay Compensation/Laybacks

Delay comp can be rather difficult to understand. I know I have spent way to much time trying to figure things out.

There are a few things to remember and a few tests you can perform to see better understand the affects of delay comp.


Things to remember...

When playing back on Pro Tools, you should have the delay comp menu item selected. This will compensate for delays (such as D/A delay).

When recording into Pro Tools, in the I/O Settings dialog you should have the "Compensate for input delays after record pass." checked.

When laying back both audio and Avid video from Pro Tools to a video device (DigiBeta for example), the video device may not be properly compensating for it's own A/D delays. This can cause the audio and video slip relative to each other.


A test you can try...

If you have a second Pro Tools system handy or even a second computer with any generic 2 or more track recording application, you can record BOTH the audio and video signals as audio signals into the second Pro Tools system. Create audio and video media with 1 frame audio pops and 1 frame color bars against black that match the audio pops. If you zoom to the frame level you can see the relationship of the audio and video signal in the audio waveforms.

As for a few more details, you can easily record a PAL or NTSC video signal as an audio signal and see the individual fields. If you record black video going to color bars or white video, you can very distinctly see the transition. If you just record ordinary video, you can still see the fields separated by little troughs.

If you record both audio and video into a second system, you can zoom in to see the audio/video synchronization. By turning on and off delay comp you can see the audio move with respect to the video.

Doing this test will help you understand how Pro Tools is handling delay compensation for audio and video. You can also try this trick with generating LTC or MTC and recording that along side of audio pops. Once you understand how Pro Tools handles delay comp you may find issues with your video recorder introducing additional delays.

Happy Delay Compin'
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  #7  
Old 08-18-2007, 12:10 PM
CharlesL CharlesL is offline
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Default Re: Delay Compensation/Laybacks

Quote:
Hef,
If you are using Delay comp and then recording to a track you must control+apple+click on the delay comp box on the rec track in the mix window to disable protools from turning off delay comp for that track. This turns the writing blue. When you rec enable a track the Delay comp is disabled for that track that is why you are getting different readings. When you disable it then delay comp is always on, on that track so everything should line up correctly.
Hi mate,

I never had to do the control-apple-click thing on the recorded tracks, and my recorded files lines up visually fine with the original regions. (ie. when i compare the waveform of the recorded sync beep to the one that it was bussed from, they looks visually aligned when i ZOOM IN all the way)

What should I look out for, to make sure that it is correct?

All my regions are bussed to Aux busses according to the stem groups they belong to (ie. VO, Dialog, Music, FX) and then goes into a full mix audio track and also the individual stem's audio track simultaneously. There are also Master Faders with their own L2 inserted to control all the individual stem's main group.

Volume automation, however, is done on the stem group's Aux buss.

I set Delay Compensation to Long.

There is also a stereo Audio track that consists of the 1kHz reference tones and sync beeps, and this track is also bussed through an Aux buss and then fed into the individual stem's recorded tracks.

Some jobs require two tones (ie. 1khz for the Ch1/2 and 400Hz on 3/4 on the Digibeta), so for these, I would have another set of tones track.

During Editing and final mix, I would usually have an Aux track (Stereo) that have the same buss inputs as the Fullmix track, and i'll monitor the mixes through it. It's output goes to Pro Tools main outs (ie. A1/A2 on most setups)

Sometimes, i'll just turn on input monitoring (The Green "i") in the Fullmix track and bypass this Aux track and monitor through this track instead.

Also, if the job requires DA88s, i will usually record the stems as tracks first (Delay Compensation On), and then import these stems into a new session, and turn off delay compensation when i layback to DA88s.

There should be a way to simultaneously buss those tracks that needs to be undipped for DA88s, so that we could record ALL the components (Fullmix, Mix minus Narration, Music undipped, FX undipped, VO/Narration & Dialog/Interviews) at one go.

But sometimes i need to bring the mix to my LE rig in room B, i would usually limit the total busses used to 16, because room B is still on an 001

So, are my routings correct?

Thanks & Regards,
[Charles]
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  #8  
Old 08-18-2007, 12:30 PM
CharlesL CharlesL is offline
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Default Re: Delay Compensation/Laybacks

Quote:
Things to remember...

When playing back on Pro Tools, you should have the delay comp menu item selected. This will compensate for delays (such as D/A delay).

When recording into Pro Tools, in the I/O Settings dialog you should have the "Compensate for input delays after record pass." checked.


Hi mate,

So, if I am doing Audio laybacks to DA-88s or Video decks, and if delay compensation is turned off (from Options, not Playback Engine) , do i still need to check the "Compensate for input delays after record pass." ?? and how about the ""Compensate for output delays after record pass." for outputs?

What about when i am recording VOs to picture? (I would usually turn off Delay Compensation (from Options) during the recording sessions anyway..)

Thanks!
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  #9  
Old 08-20-2007, 02:41 PM
hef hef is offline
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Default Re: Delay Compensation/Laybacks

Quote:


When playing back on Pro Tools, you should have the delay comp menu item selected. This will compensate for delays (such as D/A delay).


are you talking about the item in the "Playback Engine" settings or the one in the I/O setup or both?


also, like i said earlier when laying back with delay comp on, audio seems to be a a bit early- about 15-20 subframes. this is when laying back straight out of my stems-dia/mus/sfx to digibeta. i put a tone on a dia track, a mus track and a sfx track- its all starting at the same time on the digi but about 15-20 subframes before it does in the session.

if i bounce those stems to a full mix track in the session and then layback that track to digibeta without delay comp, everything is spot on. i take it this is the best way to do it.
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  #10  
Old 08-21-2007, 06:35 AM
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Marco Bernardo Marco Bernardo is offline
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Default Re: Delay Compensation/Laybacks

Hi,

Talking about delay compensation bug, i've just see that my "print" to tape (digibeta) from any of Protools 7.3.1 cs3 at work never "print" the exact timecode that protools have, always 2 frames earlier.
The delay compensation is on and set to long, because i use Ren Eq2/Waves L3/ Paz Meter on my final master 3853samples to be more precise.

The Playback engine is set:
512 samples
2 processors
80%
64voices (2dsps)
48khz
Long (4095 samples per channel)
leve 2 (default)

Too wierd because everything is sync only the timecode is diferent. I never had this problem with the 7.1 and 7.2 versions. I need to make a offset of 2 frames to put everything right (redline external time code offset)

the other wierd thing is, why is compensating earlier and not after?!

Anyone have the same problem?!

Regards,

Marco

ps: sorry for my english!! :|

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