MAutoAlign - Orchestra recording - varying delays on every analysis

[wonshu]

Hi there,

this is probably something that I don't understand and I would like to clarify why it's happening.

I have a recording of an orchestra with 23 mics, instantiated MAA on all tracks and hit analyse. Everytime I do so MAA calculates a different delay.
I find this confusing, why is it happening - I mean the mics are static and nothing changes within that same take...?

And a second question: in this case, shouldn't the center microphone of the Decca tree be set as the "master track" and align all others to that one?
When I group only the three Decca Tree mics together, the MAA instance of the right channel consistently gets a delay of 0 while the left and center channel get delayed. I know for the end result it doesn't really matter to which one the signal gets aligned, however, my OCD tells me that the center mic should not have any delay and the others should be phase aligned to that one.

-W

[mibby]

If you do a search for MAutoAlign you'll find a number of threads regarding this topic and how to use the plugin. Basically, MAA is for aligning close mics and automatically picks the best settings for you. You can't set an instance to be the "master".

Incidentally, Nugen Audio has a free plugin called Aligner which does allow you to set the "master" instance. They recently had a survey and gave away the plugin for filling it out. I'm not sure if it's still active or not though...

[wonshu]

What confuses me, is that MAA picks a different delay setting every time I hit analyse. Shouldn't "the best setting" be the consistent result everytime it analyzes the same audio? Sort of like a hash is always the same when the input is the same?

[sparella]

By different, do you mean 1 sample different or many milliseconds different every time?

[sirmonkey]

Do you have any effects on any of the tracks? Maybe something is introducing a random variable or several.

[wonshu]

Thanks for the follow up.

Many samples different (in the hundreds) and several miliseconds different every time.

MAA is the first plugin in every channel. Perhaps I do a test and remove all the EQs that are after the MAA in the channels (mostly just low cuts on the direct mics), but really this shouldn't make a difference as the signal of each channel should (...) hit the plugin at the same time. But I haven't written the host (Logic) myself, so I can't guarantee that it's doing it, however, I do trust the developers of Logic to not have screwed that up.

[sirmonkey]

I'm pretty sure that ANY plugin introduces more than zero latency (however small). This could throw off MAA (I think).
Maybe try putting MAA as the LAST plugin on every channel instead of the first. Then, in theory, any latencies, which could be different for each channel, would be "accounted for".
Know what I mean? Worth a try!

[wonshu]

Hmmm... that would mean that the host isn't handling plugin latency correctly. I doubt it. And if I recall correctly in the MAA documentation it said to instantiate it in the first slot.

[MeldaProduction]

It all depends on what you are analyzing - I assume you have a mic on each instrument, or a grid of "overheads" (if we can call it that way). In that case it cannot really work well, because the mics are actually recording different instruments. MAutoAlign only makes sense if you have one instrument recorded by multiple mics, so that there is an actual physical delay. In your case there is no "solution" for the phase difference equations, since every signal is basically uncorrelated, so the plugin just chooses the "best fit", which most likely sucks.

So a general rule of thumb: Use MAutoAlign only for mics recording the same instrument and all of them from a near proximity (since ambience becomes uncorrelated again).

[wonshu]

Ah, now I understand.

Yes, orchestral recordings are multiple (many) microphones, some of them for all instruments (Decca tree, outriggers, etc...) some of them "direct" mics on the sections, and also single mics for the section leaders.

Ok, so for this use case I don't need MAA.

The numbers and clearly logically thinking about it should have told me, but sometimes excitement gets in the way.

[MirkoVanHauten]

Try autoalign from soundradix. Usually gets you exactly and reliably where you need to.