Ableton Forum

I'm trying to match a long (2+ hours) audio file to another one. They were recorded at the same event.
The reason they are not syncing up was originally a sample rate mismatch. Long story short, resampling either file is not an available solution.

My QUESTION:
When shift-click-dragging the shorter file to match the length of the longer one, the audio is still mismatched afterwards.
It seems that the warp engine does not evenly stretch the audio, even in complex-pro mode (or any other mode).
I've also tried first setting a marker to the very end of the file in question with the same issues resulting.
What am I missing? Can Ableton actually do this (stretching audio completely evenly between beginning & end of the clip)?

Right click on the first warp marker and select "Warp Straight from here" i think.

Cheers
D

Are there a lot of tempo changes in this long clip?

This seems almost less like it needs a ‘warp’ solution, and more like it needs a periodic offset solution. Using one clip as a primary reference, and just lining the other clip up unwarped… finding spots where it drifts and then splicing.

If the issue is not drift but sort of a consistent ‘pitch-stretch’ related issue, then you might need to resort to warping. For that, I’d not let Live do the warping. I’d warp manually in a very specific way.

I would have a reference clip unwarped, we will call it A, and temporarily determine a Start reference point that I can also use as a reference point on the other clip, we will call it B.

Then with A I would also determine a clear End reference point (where the clip is only as long as it ending on that position). On B I would have warp on and clear out all the markers. Have only one warp marker at the Start reference point. Have the ‘end’ of B be the exact same spot as the A clip… as in, the same ‘ideal’ position… they might not line up exactly, but the beginnings should be perfect.

Next use the shortcut to ‘stretch’ an audio clip on clip B to pull the ‘end’ using your mouse pointer until the end matches up with the ideal end point on clip A in Arrangement view. At this point the beginning and end should then be the same content and be lined up on arrangement.

I forget the stretch shortcut. It is holding a key and dragging one of the corners I think.

After this, you can THEN put a warp marker at the end of clip B to kinda keep it there… if there is drifting inside the 2 hour span of the clips, find a spot where they drift the Furthest from each other and add a warp marker to clip B … then drag that marker so that it stretches and aligns with clip A.

Sorry if this sounds so abstract. It’s kinda my attempt to understand and give you ideas of a possible solution. Good luck!

Thank you. Yes, so the difference in length is a result of one clip's origin being in 44.1 kHz and the other's in 48 kHz. A simple resampling of one clip to the format of the other would've done the trick, but the 44.1 kHz clip had already been mixed and re-exported as 48 kHz, effectively "baking in" the length.
I've tried fixing this via ffmpeg, unsuccessfully.

This may all sound overly convoluted, it was a rare case where there was no easy fix.
The easy fix would have been to warp the entire clip (shift-click-drag the edge of the clip), BUT that always warped the file inconsistently, regardless of warp-mode, or grid setting. That's the part that caused me to come on here to see if anyone knows WHY it's not able to create a clean, mathematically consistent expansion/contraction, or otherwise what I might be missing.

I finally got a close-enough fix by creating warp markers at the first & last hard transients of the clip, and then dragging (warping) them to line up with their counterparts on the other clip. In that case, it did warp the audio been the two markers evenly.
Would love to understand the exact machinations of the warp engine under the hood.

Part of the reason why I asked about tempo changes is that, if there are no tempo changes, then you should be able to warp clip A also, and set that as a ‘Leader’ type clip that forces Live’s Arrangement tempo to match it bar for bar. Then you could match clip B to it bar for bar instead of sort of warping arbitrarily just to match the duration of the clip.

The reason this can be favorable is that some warp modes do use the quantization of beat divisions to warp a clip.

The warp modes are described in the manual. The Complex modes basically do time stretching in a more deep processing kind of way. Many of the warp modes just chop a clip into tiny bits in a variety of ways. There is also a vinyl/repitch mode that simply stretches/compresses by speeding up or slowing down the clip which results in pitch change (probably not ideal unless your pitch was affected by your different rates).

All the warp markers do is indicate to Live what the tempo of a section of audio is ‘supposed’ to be from the point of the marker all the way up to the next marker. For tight steady tempos, you can have one marker set that can indicate the tempo for 100 bars straight. For a clip that has a human feel or even one that fully changes tempo over time, you have to add more and more markers….

… the thing is, these markers are meant to force the clip to fit into the Global tempo. So if a marker indicates a tempo change fast to slow and then fast and it IS warped correctly, then on the arrangement the clip will change with No change in tempo (might sound a little funny as it’s stretched or compressed in time) , no change in tempo UNLESS the arrangement itself has the tempo changes indicated on the timeline.

In your particular case though, warping clip A might actually do more damage because then you’re potentially changing the tempo of clip A and then trying to compensate through clip B. Can be done but could be time consuming with probably a worse result. Keeping clip A clean (unwarped) is good, unfortunately won’t necessarily fit the arrangement timeline, but you’re only trying to match a Clip to a Clip, not matching them to Ableton Live’s Arrangement for deep production. Warping usually will result in some kind of artifacts. The various modes are there to decide a method that could make them least obvious (or more obvious if you’re feeling experimental).