I/O Plug-in not compensating for hardware bounces

[taylorherbert]

Hi, I've been tearing my hair out over this one. I'm using Logic 9 with a PowerMac 8core with 10GB Ram and an Aurora Lynx16.

 

I'm trying to run stem mixes out through my hardware and then back into Logic. The mix is pretty complicated, and no matter where I put the I/O plugin it will not compensate for the latency and the recorded track is always late by several thousand samples.

 

Here's my setup: I have about 8 to 10 drum tracks routed to bus groups (Kick, Snare, Overheads, etc.) and processed in parallel via an Aux send through a UAD compressor plug-in. The group busses and parallel compression buss are then sent to a master drum bus sent. The Master drum buss is sent to an Aurora Lynx 16 Outputs 3-4 to various hardware processors and then back to Recorder inputs 1-2.

 

I've tried the I/O plug-in set to Output 3-4 and Input 1-2 on the master drum bus, the individual tracks, the group busses, or the parallel compression buss. The pings are +28 on just about every track, but the resulting recorded audio doesn't line up. I also tried the record offset to +28 and -28 and that didn't work. The record offset set to about -4700 samples is about the closest I've been able to come to getting it lined up.

 

I've also tried to bounce my guitar bus in a similar way, just two tracks sent to a bus, sent to a stereo output. The I/O plugin placed on one guitar track makes the guitars out of sync, when placed on both tracks it doesn't line up with the original audio, and on the buss it also doesn't line up.

 

What is going on, and how do I avoid having to line up my tracks by eye everytime I want to bounce a stem? This is really impeding my ability to get my work done.

[fader8]

Read this thread:

http://www.logicprohelp.com/viewtopic.php?t=41101

It's old and refers to Logic 8 (pre-ping feature) but it explains a few things.

 

Things changed in Logic 9, but the principle of how PDC operates is the same. Aux channels get delayed, but track audio is played back in advance and subsequently so is bus audio. Remove the I/O plug-in from your aux channel. Open the environment mixer layer and create a new channel strip: Bus. Set this to the bus number that is feeding the aux channel you just removed the plug-in from. Insert the I/O plug on this bus channel strip. Ping. Try this out.

[taylorherbert]

I'm not using an Aux track as a parallel send to hardware like in the example, I'm combining several Aux track outputs into a final stereo Aux track that I'm sending to a pair of Outputs.

 

Here's pictures of my setup:

http://dl.dropbox.com/u/30830784/Channels%201.jpg

 

http://dl.dropbox.com/u/30830784/Channels%202.jpg

 

So what I should be doing is this?

 

 

http://dl.dropbox.com/u/30830784/Channels%203.jpg

[fader8]

This is a tricky one. Because of your routing, track to bus to aux to bus to aux to stereo out, with the I/O plug on the final mix bus, (or the aux, in this case I don't think it matters) then it may fall outside what PDC can handle. I can try it here, but I'm probably not running the same version of Logic as you are and I believe there have been changes to this in recent versions. There are certain cases of channel types and routing, particularly when using the I/O plug or External Instrument plug where effect plug-ins don't report their process delay to PDC.

 

You do have PDC prefs set to "All", right?

[taylorherbert]

Yeah PDC is set to ALL. I'm running the most recent version of Logic. If I/O plug-in is not capable of adding up all the latency, is there some 3rd party plug-in that can?

[fader8]

Zip your project file, no audio, just the .logic file and post it here so I can test your routing. There are a few things we can try.

[taylorherbert]

Man, that's huge. Another engineer is running a session in there all weekend, but I'll definitely try to get that to you on Sunday evening. Thanks a lot for being so responsive.

 

-Taylor

[nosebagger]

Hey Taylor,

 

Looking at your routing, I think the problem may be that you are trying to record the signal before it's completed its journey through Logic's mixer. PLC ensures that Audio is in sync when it reaches Logic's output channel strips - which means that it won't necessarily be in sync prior to that point. 

 

Use the IO Plugin (make sure you ping, double check your IO setup is correct, and move it to Aux 4 - unless you have a reason for putting it on a Bus), then try printing your drums by looping the Stereo Output back to a spare stereo input, and record to a track set to those inputs. Also, when recording the loopback, make sure that either Software Monitoring is off, or Low Latency Mode is set to On.

 

Sending Aux 4 to a spare bus and recording to an audio track set with that bus as its input may also work, as should realtime bouncing the Stereo Output.

 

Hopefully this will sort it out, but if not, I'm sure fader8 will come up with something!

 

Tom

 

(Also, has your system's recording delay by been calibrated by running a loopback or ping test?)

Edited October 8, 2011 by nosebagger

[fader8]

Hey Tom,

Yeah, there's a lot of odd stuff in that routing. And where is bus 7 going? Anyway, using sends on aux return channels so liberally stacked like this can create PDC problems by itself. Throw in an I/O plug in the middle and you've got some issues for sure.

[nosebagger]

It's an intricate routing for sure, but I think PLC will handle it - although I don't have much direct experience with UAD plug-ins. The key should be to print the audio from the right point in the signal path, i.e. not from the inputs returning to the IO Plug-in.

 

Where's Bus 7? That sounds like my trip to work!

 

Tom

[taylorherbert]

Hey Nosebagger, thanks for your input.

 

I had to take those pics on my laptop, which only has 2 ins and outs, so the routing is a little different on the studio computer. On the real version of that routing, the Aux track from Bus 4 is going to Outputs 3-4, and the record armed channel is coming from Inputs 1-2.

When I originally tried to bounce this track, I did have the I/O on the Aux channel strip with the appropriate inputs and outputs selected, and it gave me a ping of +28 samples. Looking at the resulting recorded waveform it was more like +4700 samples. Same thing if I tried to put it on the Snare Top track, except that just made the snare track out of sync with all the other drums.

 

Bus 6 and 7 are going to different mix reverbs in Space Designer on Aux tracks going to different outputs.

 

I haven't done a loopback test or ping other than what's in the I/O plug-in. On tracks with simple routing (mono bass out and back in with no bussing, for example) the I/O trick works fine, and I get +28 samples pretty consistently. It's only when I bus multiple tracks to an Aux, that things get out of sync.

 

The UAD plug-ins are pretty laggy, if we're doing overdubs with UAD plug-ins anywhere on the mix, we've got to run low latency mode or the recorded audio is out of sync by a 100 msec or more. When mixing in the box the PDC seems to do a good job of keeping everything in line, though.

[nosebagger]

Hi Taylor,

 

I haven't done a loopback test or ping other than what's in the I/O plug-in.

 

Make sure you run a loopback or ping test on the system with a new empty template, routing the output directly to the input, and enter the offset needed (which depending on your hardware may well be zero) in the Recording Delay Preference. Once done, you won't have to touch it again, as it will act globally across all projects to ensure that all overdubs and loopback recordings are placed correctly.

 

As for your stems, I'm assuming that the sync problem doesn't occur on playback, but only when printing them?

 

If this is the case, then following the methods in my first post (which I've just edited with extra information) should see you right.

 

Tom

[fader8]

Taylor,

I ran some quick tests this morning emulating much of the odd routing you have in your project as best I could. I haven't tested this stuff since back in Logic 8 days and I must say they've fixed a lot of niggly PDC issues in Logic 9.

 

Theoretically your mix should work. Be sure you're bouncing in realtime to print stems rather than recording them to a track so that the Record Delay setting doesn't enter the picture.

 

The most likely cause is that you are using a 3rd party plug-in somewhere that is not properly reporting its process delay to Logic's PDC system. This isn't entirely uncommon. I recall Izotope Ozone having this issue for a long time until they fixed it. The easiest way to start testing for this is to make a copy of your project and remove all plug-ins except the I/O. Don't bypass, you must remove them completely from your project. Test bounce in realtime. Drag the bounce to a new track, select the region and use the "Move Region to Original Record Position" command.

 

Does this audio line up?

[taylorherbert]

Sorry it's taken me so long to get the /logic file to post. Here it is.

 

@Fader8: What do you mean by real time bouncing rather than recording to a track? I thought to be able to run things to hardware you had to record it back to a track?

Darkness by the Roadside OTB Diplomix.logic.zip

[fader8]

OK, I'll take a look as soon as I can.

 

Re. Real time bouncing, yes, you should use it because it eliminates the interface variables. Works fine with external effects. Do it all the time here.