Strange ADC behavior?

[TiPo]

Here we go.
In my recent session I have found out that the ADC compensation values are inconsistent.
In this particular session all the Instrument tracks are compensated properly but none of the Aux tracks are compensated by the mathematically correct value and the compensation values are not even close to where they should be.

For e.g. ReVibe gives a delay value of 2 samples thus if the longest delayed track (that is an Instrument Track in this session) is delayed by 861 samples than the Aux track that only holds the ReVibe plug-in should be compensated by a value of 859 but it is not!!! The value here is 591! This gives a total compensation of 593 samples (591+2=593). And this is totally off.

There is another Aux Track with Short Delay II on it where the ADC value is 694 samples + the Plug-In Delay value of 4 samples result to a total compensation value of 698 samples and again this is wrong. This is short again by 163 samples from 861!
On the Audio tracks the total ADC is short by 10 samples but they are at least consistently off by 10 samples no matter what plug-ins are on them or how many.

The only tracks that are properly compensated by the ADC are the Instrument tracks with various instruments on each (e.g. Indigo, Stylus RMX, Atmosphere...etc) followed by other plug-ins (EQ, Compressor...etc). They are all compensated correctly to the total value of 861 samples.

I have to add that none of the indicator numbers are colored in red in the Delay Compensation views (that show the actual Plug-in delay, User Offset and Track Compensation values) that would indicate that the actual System Delay has exceeded the allowable delay amount set in the Playback Engine panel. All of the indicators are in green color except the once that are in orange color and are indicating the System Delay that is the highest, in this case it is 861 samples.

All I could do to remedy the situation is to correct the improperly ADCed tracks manually by disabling each of their Delay Compensations and type in the value of 861 samples into the Manual Offset field in the Track Delay window.

The session is 44.1KHz and 24 bit
Pro-Tools HD 7.3.1cs1
Apogee Rosetta 200 +96I/O clocked by Apogee Big Ben
OS X 10.4.8 on a Dual 2GHz Mac G5/ 4.5 GB DDR SDRAM


Can someone please enlighten me about what is going on here with ADC?

Thank you.

TIPO

[Danny Caccavo]

It's really difficult to say from your description what is going on. I don't know what your bus routing or send usage is. The only way to tell what is going on is for us to have the session in front of us.

Also, I can't tell if your math is correct without knowing more about the session.

However - are you hearing phasey audio or anything that just sounds incorrect? If the instruments are reporting 861 samples, that might be incorrect - instruments usually report very little. Does the amount that the instruments report vary by the hw buffer size, and is the number the same on subsequent opens of the session? When you print the result of an instrument plug-in, is the audio in the right place, or is it advanced? Please list the instruments you are using, thanks.

Are you using RTAS audio plug-ins on aux, or just TDM on aux?

If there is a definite problem in the audio, we'd be happy to take a look at your session.


Danny Caccavo
Product Manager
Digidesign

[TiPo]

Hey Danny,

Thank you for the reply. I will get back to you with a detailed step by step session description with pictures of the session setups.

Thank you.

TIPO

[iamnerdyrocker]

Don't forget, ADC also compensates for any mixer busing you have created as well. Sending signals to an Aux Input has some delay already associated with it so that is built in.

[TiPo]

Hey Danny,

Here is the complete session TEST I did. Pictures included and descriptions.
Please tell me if it is normal ADC behavior so I will know if I should do the manual user offset compensation or not.
Otherwise there is no phase problems. At least I don't hear any!

Please click on this link: ADC TEST

Thank you.

TIPO

[TiPo]

Hi Danny,

Were you able to look at my ADC Test results?

Thanks,

Tipo

[TiPo]

bump

[Danny Caccavo]

Tipo -

You need to get your actual session to tech support for us to look at. By "we'd have to look at your session" I meant more than screenshots. It would take many hours to decifer what is going on just by looking at your screenshots.

There is a design limitation in Delay comp to look out for, thoug - Master faders can *report* a delay, but since they are just spigots, they do not have mixer inputs that delay can be applied to. So an example like the following could cause a problem -

Session with 2 mono audio tracks, 2 stereo master faders, and 2 stereo aux tracks
Route track 1 to bus 1-2, track 2 to bus 3-4
Assign Master fader 1 to bus 1-2, and master fader 2 to bus 3-4
Aux track has input from bus 1-2, second aux track has input from bus 3-4
Both aux tracks outputs assigned to outs 1-2

Now, if you add a plug-in to one of the master faders, but not the other, you will have a problem. If you want that type of scenario to work, you'll have to either use the same plug in on both master faders, or use time adjuster on the other master to make up the difference.

Check your session over to see if you have something like this. If not, I'll have someone from tech support contact you, provided your contact info in your profile is correct.

Danny Caccavo
Product Manager
Digidesign

[bashville]

Today I went to record using my blank template session. No audio recorded into it yet, but it had a complete bus setup, with dual busses for the drums, then some aux layers before the master for striping mixes onto a track instead of bouncing. My drum bus setup already has plugs inserted. Delay compensation was on.

I created a new aux track to monitor my mic (output of that channel feeding directly to main master) and I'm hearing delay on the input. I thought that delay compensation was supposed to be automatically bypassed anyway, but I command-control clicked on the display to disable it anyway. I still heard delay. I played with ADC settings--no change.

It's not until I deleted all the drum auxes with all their plugs and bus assignments that the delay went away. So it's clearly related somehow to ADC, but it wasn't behaving the way it was supposed to! I wasn't using any master tracks for bus effects.

Can anybody spot user error in this scenario from what I described? I'm running 7.3.1 cs1. PT HD Accel on a dual 2.0 G5 if it makes a difference.

Thanks--Kevin

[Mark Dann]

I'm not sure if I totally understand your scenario, but I also use multiple auxes in front of the master fader to print mixes. Some of these auxes have plugins, some don't. There are also plugins on the master fader. I find I have to do the following:

- Read the amount of delay from the DELAY INDICATOR on the master fader
- Type this same number into the USER OFFSET on the aux channels

Voila! No more delay issues. At least for me.