Topic: drift in laptop matrix...fix in post?

[goodcooker]

I did a freebie for a guy who has done some soldering and stuff for me (Dan from Direct Pro Audio) and I've got problems. They are called Fork in the Road...good band good original stuff....so anyway I wanted to do a good job for them but also wanted to try something new.....laptop four track matrix with Adobe Audition 1.5.......and to add more chaos frtower loaned me his V3 for a test drive and I wanted to use it...real bad.

So here was the setup  SP C4s(omnis on stage)>Audio Magic XStreams>V3>spdif>UA5>usb>lappy
                                board patch>Tascam us122>usb>lappy
all files recorded mono (track1 stage left track 2 stage rt track 3 board left etc....) at 24/48.

I wanted to be able to mix it all down in post with as much flexibility as possible.......so here's the deal.
The 2 sources have a considerable amount of drift since, I assume, they were not synched to the same wordclock (neither usb device supports this as far as I can tell). There is a digipop sort of noise at about 2 mins in and by the end of the set I would guess is up to about 3 full seconds.

I really want to salvage something for these guys b/c they were just really nice and Dan offered to put some new right angle Neutriks on my AM cables as a gesture of thanks...

so what I'm getting at is can the drift be rectified by finding the same moment in the two sources. cutting off the excess and stretching (or shrinking) one to fit the other???........I think there is such a command in either Adobe Audition or Audacity but I don't really know how to begin...if it's off by more than a few milliseconds it goes from sounding pleasantly out of phase to horrible.

or should I just scrap the thing, tell the guys I'll do it again and bring the Presonus Firebox and a few extension cords since I can't find a batt for it?

any help greatly appreciated.

[John Kary]

The problem you are experiencing is very common when trying to matrix two sources.  There should be a Wavelab Matrix guide on the forums somewhere that details how to address drift.  It will _always_ happen unless you are using the same worldclock for both sources.  Below is how I deal with it.

My solution is to manually sync the 2 recordings as close to the head of the recording as possible.  Then goto the end of the set and find a sync point, like a definite drum-hit or other spike in the waveform.  Use the time display of your DAW and measure the distance in milliseconds between the two points by selecting the space between them or doing math on the cursor position for each.  Then stretch the mic source by that many milliseconds (look up how do it in your DAW.)  I personally stretch the mic source because it is usually mixed lower when I mix them and any slight flaws as a result of stretching will be hidden by the louder soundboard source.

Good luck!

[iriewsp]

Definetly a clocking issue.  The spike/digi pop could also be a clock issue..

First question is in your software were you clocking internally or externally?
USB should have had some sort of clocking option.  I clock internally with pro-tools while being connected to my hardware via usb or firewire.

Anyway though you can salvage the project.  No problem.  You can do it the above stated way.  Or you can do it many other ways.  You can split one source up(usually the slowest) to where it lines up every 5 minutes.  My favorite way is to run it analog out via a good D/A then back in through a good A/D.  This often makes my life allot easier. 

Bottom line though, its still not going to be as good as if they were clocked properly.  I say do this for fun, and still give it to them.  Then go back out and do it again the other way you mentioned.  Just so you know the difference.