MAutoAlign “unsyncs” items during rendering in Reaper

[Mark the Harp]

I did a recording of a choir recently with a main mic and another recording from someone else’s machine halfway down the church. Managed to sync the two stereo recordings perfectly in Auto Align, but I’ve noticed that after rendering, they are no longer in sync.

Have gone back into the Reaper project and they are in sync when I play it there, so I’m not entirely sure why the audio appears to have gone out of sync during the rendering process.

Can anyone suggest some experiments I could try/ something I’m doing wrong? Does it require “locking” before rendering? Though I think I’m doing everything required.

[Mark the Harp]

Just an update for anyone else who is using this plug-in with Reaper:

After some experimenting using Reaper, the shift from being in sync to out of sync when exporting happens if I change the sample rate of the export file. For example if the project is 96k, and I export at 96k, the exported file works just as it did when I was playing it in the project. If the project is 96k but I change the export to 48k or 44.1k it changes the sync of the aligned items so they are no longer time-aligned.

This is slightly irritating since I often work at a certain project rate and decide to export at some different rate – sometimes several different rates. For example I might export at 96k for some sort of onward external process like noise reduction or for archiving, or 44.1/48k mp3 for listing/online sharing.

Not entirely sure if this is a function of how this plug-in works or if it is peculiar to the way Reaper handles sample rates.

It’s a little bit irritating obviously because the time – alignment needs to be redone each time I want to output at a different sample rate to the project sample rate. The problem also occurs for example if I have a 48k project and export at 96k - again unless the two are set to the same rate, I get a shift, so the rendered file does not represent what I was hearing while I was editing.

[davidlincolnbrooks]

How "un-synched" things get depends on your milliseconds setting, which YOU can specify. If I have two tracks that need to be in strict synch (usually because they are percussive in nature or have a sharp attack) then 10ms is the farthest I'll go. On the other hand, if I have two sustained pad tracks, then I'll happily extend the milliseconds setting to 18ms, 20ms, 22ms.

[Mark the Harp]

Cool - these were two separate machines so typically 400mS or so. But the issue is not that they can’t be synced, it’s that when I get them synced and then render them at any different sample rate from the one the project was set at, they go out of sync. I guess it’s just how AutoAlign works (with Reaper anyway).

[MeldaProduction]

Thanks for the info. I'll check it out. However note that it's generally not recommended to change sampling rate for rendering, as, well, who knows what will happen .

[MeldaProduction]

Oh I know - MAutoAlign stores the exact delay in samples, which obviously changes time with sampling rate, should be easy enough to fix.

[Mark the Harp]

Got it. I’ve used it on complex mixes but never spotted what was going on until I did this simpler thing. Hope this is useful though for anyone who does what I do (exporting at different sample rates). I can work round it now I know what’s going on. Cheers!