Time Stretching + Marker Mayhem

When time stretching in a montage, markers move unexpectedly. I was wondering if anyone has seen this or has an idea how to avoid it?

Here’s an example. I have two versions of the same recording, each at a different pitch. The top track is two clips, each about 45 minutes long. They “meet” at a tape flip and I want to patch the gap with a few seconds the bottom track, which is about 8 minutes long, but the clip has been resized to about a minute so it’s easier to work with.

The orange markers are attached to clips on the top tracks and the blue are on the bottom. To match the bottom to the top, I want to time stretch the bottom so that the two markers on the right – one orange, one blue, highlighted in the markers window – line up. You can see where the cursor is for “time stretch to cursor.” I’m just eyeballing it, which is fine for what I’m doing.

It you look at the marker offsets, the highlighted blue one is about 8 minutes into the bottom track, which, again, is resized, but it’s about 10 minutes long. There are actually 3 markers on the bottom track, two blue and one yellow. You can tell them apart because they have offsets of 7+ or 8+ minutes.

After doing a time stretch to cursor, the audio is shortened to the cursor as expected, but the blue markers have moved unexpectedly to the right by about 7 minutes.

A little investigation shows that these three markers (two blue, one yellow) that moved unexpectedly are the ones attached the clip on the bottom track, and they have a new offset based on the left edge of the resized clip, rather than the start of the clip like before. In other words, instead of being 7 or 8 minutes from the start of the clip, the markers are now 7 or 8 minutes from the left edge of the resized clip. I’ve measured it below:

My expectation was that each marker would remain attached to the same audio samples of the clip it was attached to, and that its offset would change by a few seconds, but it would be in the same “place” with respect to the music itself. But it seems like both the offset and the starting point for the offset changed, and because of this, the marker is nowhere near the audio samples it was attached to. This sort of makes sense, because the clip on the bottom track has been in a sense rendered and it cannot be resized any more, etc. The markers are still attached to that clip. But it seems like the marker offsets should be recalculated to reflect the total size of the new, time-stretched clip…?

BTW, I believe that these new offsets are mathematically equal to the original offset minutes the % reduction of the overall clip from the time stretching. Since I’m stretching to the cursor, not by a fixed %, I can’t tell for sure.

This raised another question: When I time-stretch a resized clip like this, is the % change being calculated against the entire clip, or just the resized clip? In other words, if the entire clip is 10 minutes and the resized portion is 1 minute, and the cursor is placed 10 seconds before the end of the resized clip, is the time stretch 10% (10 seconds out of 60) or 1.6% (10 seconds out of 600)? It would have to be 10%, right? Otherwise, the beginning of the resized clip would also move…?

Whew, that’s a lot to digest. If anyone wants to play around with this, I think it’s easy to reproduce: Just throw a single track or two into a montage, add markers with references to the beginning, end and also the audio samples of the clip, and time stretch. I think that you will see strange marker placements.

I have difficulties following your case but did a test with WaveLab 11.1 and I see one problem indeed:
if the clip’s left edge does not correspond to the audio file’s start, then the marker is not shifted as it should. I will see if there is time to fix this before WaveLab 11.1.10.
Note that this clip attachment is needed:

The percentage is about the visible part of the audio within the “clip’s window.”

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