Automatic Delay Compensation - LE and HD sessions

[milet22]

I'm primarily an LE user but I mixed a project on an HD system recently and am hoping someone here could explain sync issues I had.

When I transfered my LE mix (with plugins, buses, etc.) to an HD system, I found that the timing of the tracks relative to each other was off so I realigned everything until it is was fine again. When I later returned the session to my LE system, everything was out of sync again (but in a different way).

I'm guessing this has to do with the different ways PTLE and PTHD handle latency. Is there a way to move sessions and mixes between the two systems without losing sync? I experimented with turning on HD's Automatic Delay Compensation when I first noticed the tracks were out of sync, but that didn't seem to fix the problem. Do the playback buffer sizes need to be the same, or does that even matter?

I would really appreciate any advice anyone can offer.

Thanks,
Rob

[jeff markham]

I do this alot actually . and generally don't experienced the problem that you report . with
one exception .. some of my inserts promote up and down from TDM to RTAS when going
back and forth between LE and HD. In some cases, the RTAS version has latency where
the TDM version doesn't. If you've bumped the tracks around in LE, then they will be
out of whack there too.

it's worth going through your tracks and checking the latency reported. in all likelihood,
you'll see some difference in the reported latency values on the tracks that go out
of whack.

jeff

[jjhuntfox]

I'm new to HD and I'm studying up on it now. I was reading the PT Reference Guide and there is a section on Delay Compensation. In the 7.0 book it's on page 505. You might have to save the session with the delay compensation turned off, on the HD system of course. Go to setup, playback engine and turn off delay compensation.

I'm still trying to figure out when to use delay compensation. It makes sense to use it on mixing. I just don't know if I want to track with it or do overdubs with it. The book doesn't really explain the when or why, just the how.

[dj_grimmace]

I've transfered sessions between the two systems and never had this issue. That being said, it is a very good idea to see if PT changes some of your plugs to TDM when switching to that system. It shouldn't, but . . .

Regardless, the way I understand it, ADC compensates for DSP latency. One should NOT use it when tracking. It will delay all tracks to the longest delay time. In other words, if one has a plug in that introduces 100 samples of delay, then with ADC on, all tracks will be delayed by the number of samples needed to add up to 100. This will obviously create some latency in a cue mix. You can also enter a user defineable delay time in the delay compensation window at the bottom of the mix window. (Only in HD.) If you instantiate a plug in with a delay longer than ADC can handle (I believe around 4000 samples) then one must manually move regions. This will be what might cause problems going back to an LE session.

You're HW buffer size can create some latency, but should not affect alignment of individual tracks.

Hope this helps.

Matt Grimm

[milet22]

Thanks for the feedback so far.

When I was working on the session, I did change some of the plugins from RTAS to TDM (or vice versa) as I was running out of CPU power or alternatively DSP power. From what some of you were saying, this would cause the issue? If that's the case, what's the best way to handle the situation where some plugins are RTAS and others are TDM?

As for ADC, after I noticed the delay issues, I enabled it, but it didn't fix the problem. Based on the responses, if ADC compensates for DSP latency, that means it only helps for TDM (or HD bussing delays), not RTAS, delays?

Again, I appreciate your help.

[jeff markham]

Thanks for the feedback so far.

When I was working on the session, I did change some of the plugins from RTAS to TDM (or vice versa) as I was running out of CPU power or alternatively DSP power. From what some of you were saying, this would cause the issue? If that's the case, what's the best way to handle the situation where some plugins are RTAS and others are TDM?

As for ADC, after I noticed the delay issues, I enabled it, but it didn't fix the problem. Based on the responses, if ADC compensates for DSP latency, that means it only helps for TDM (or HD bussing delays), not RTAS, delays?

Again, I appreciate your help.

Hi,
So, if I know i'm going back and forth between HD and LE and/or MP and I'm using plugs
which introduce delay, i basically don't use the HD delay compensation engine for those
mixes.
I go through the (ply) tracks and make a list of the plugs which introduce latency and find
the plug with the longest latency. I then make a summing bus (with an aux track) that
is the undelayed path and route all the tracks that don't have delay to that summing
track. I add a time shifter plug to delay the 0 delay tracks by the same amount as the
plug-in delayed tracks so they line up. sometimes you have to get a little creative to
make it all work out . but . it's not as big a pain in the butt as it's often made out
to be. do i wish LE and MP had PDC? yea .. it's embarassing in this day and age that
they don't and PDC doesn't influence an HD purchase decision .. i can bet big money
on that ;-)

jeff

[bashville]

Regardless, the way I understand it, ADC compensates for DSP latency. One should NOT use it when tracking. It will delay all tracks to the longest delay time. In other words, if one has a plug in that introduces 100 samples of delay, then with ADC on, all tracks will be delayed by the number of samples needed to add up to 100. This will obviously create some latency in a cue mix. You can also enter a user defineable delay time in the delay compensation window at the bottom of the mix window. (Only in HD.) If you instantiate a plug in with a delay longer than ADC can handle (I believe around 4000 samples) then one must manually move regions. This will be what might cause problems going back to an LE session.

I'm reading the ref guide starting page 507 and it contradicts this. Also on p. 157, it says you can leave it "on" all the time, and PT will auto-suspend the delay on a track you're recording onto.

I'm always leaving it on so the sounds I'm setting up in the drums don't go out of phase. I want to mix as I go, and not be guessing what it's going to sound like when I turn the ADC back on.

Sorry I don't have any LE experience--it just seems like the math would be more efficient on these systems than what's being described here. As in, being able to assume that if everything sounds in time with no plugs, that adding the plugs or bussses will be adequately compensated (in HD) no matter how squirrely you got with your signal path.

Have you ruled out all external clocking/sync issues?

[bashville]

I'm primarily an LE user but I mixed a project on an HD system recently and am hoping someone here could explain sync issues I had.

When I transfered my LE mix (with plugins, buses, etc.) to an HD system, I found that the timing of the tracks relative to each other was off so I realigned everything until it is was fine again. When I later returned the session to my LE system, everything was out of sync again (but in a different way).

I'm guessing this has to do with the different ways PTLE and PTHD handle latency. Is there a way to move sessions and mixes between the two systems without losing sync? I experimented with turning on HD's Automatic Delay Compensation when I first noticed the tracks were out of sync, but that didn't seem to fix the problem. Do the playback buffer sizes need to be the same, or does that even matter?

I would really appreciate any advice anyone can offer.

Thanks,
Rob

Upon re-reading the original post, am I right in assuming that the session was created originally on an LE system? It seems like there'd be a possibility of some parts being mis-played timing-wise into the original sequence. LE doesn't have ADC, so if you had plugs on some of those LE tracks, the players would be reacting to faulty timing to begin with. Then when you transfer it to HD, if you did some TDM-RTAS swapping and there's a difference in latency between those two plugs, you'd be damned either way with ADC on or off.

My first thought would be to not swap any of the plugs that you were using RTAS in LE, leave ADC off, then see what it sounds like. That way you'd hopefully be creating the same scenario in HD that you had in LE. If you then want to use ADC in HD, start copying down the latencies of all those plugs and actually slip the tracks around by the proper amount. Get the sequence right first, then go crazy again with the plugs in ADC mode.

[NoBoundriez]

i have a question about this whole subject... now that everyone is on it.... When you mix in HD and then transfer your files back down to LE, will the plug-ins that you put in on the HD system be transferred down to the LE version? I have heard that they do not... Actually i was told that you are not even supposed to be able to transfer files down from HD to LE since HD is the "higher" version, something about LE not being able to read the HD plug ins and what not... so the issue remains confusing for me... any help would be more than none! lol...

[jjhuntfox]

I'm primarily an LE user but I mixed a project on an HD system recently and am hoping someone here could explain sync issues I had.

When I transfered my LE mix (with plugins, buses, etc.) to an HD system, I found that the timing of the tracks relative to each other was off so I realigned everything until it is was fine again. When I later returned the session to my LE system, everything was out of sync again (but in a different way).

I'm guessing this has to do with the different ways PTLE and PTHD handle latency. Is there a way to move sessions and mixes between the two systems without losing sync? I experimented with turning on HD's Automatic Delay Compensation when I first noticed the tracks were out of sync, but that didn't seem to fix the problem. Do the playback buffer sizes need to be the same, or does that even matter?

I would really appreciate any advice anyone can offer.

Thanks,
Rob

Here is my guess... When you transfered your session to HD, the delay compensation was on on the HD system. The HD system delay compensation took out the plug in delay. It sounded off because you were used to the delay of the plugs. You then realigned the tracks on the HD system to defeat the delay compensation. When you went back to LE it was all messed up because there was no delay compensation. So you changed the alignment not PT.

I was just experimenting last night with bouncing a stereo track, with Altiverb on an aux track. With delay compensation disabled it was very wet a lush sounding. When I enabled delay compensation it sounded totally different. Much shallower, less wet, needed more gain and a bigger space. The delay compensation removed a bunch of pre delay, I'm guessing about 1500 samples worth. Totally different sound. Different enough I'd be tempted to "realign" the tracks.

What do you think of my guess?