Sync one audio track to another by 2 points

This is a feature request to sync one audio track to another, given 2 points on source file and 2 points on destination file.
That would automatically adjust the tempo speed + shift the track trimming or adding silence at the beginning.
This is helpful for example when adding additional audio tracks to a movie in a different language.

The way it has to be done now involved complex calculations, interpolation what the optimal speed/tempo would be based on a part of it. Plus you have to later on shift the track + possibly repeat the process several times.

Example: move orange points from B track to match green points from A track, leaving the timeline of track A untouched. Of course include left and right channels or desired channel.

Actually, no calculations are required in 2.4.2. Simply jot down the target length. Then when performing change speed or change tempo, simply enter the target length. Audacity does all of those heavy calculations for you. And, more accurately to boot!

I hope this helps. :smiley:

No, it doesn’t help at all. If you could provide an example please, for example (hh:mm:ss):
00:37:00 must be moved to 00:38:12
01:42:44 must be moved to 01:38:10

So it readjust the tempo/speed and shifts as well, so I just can export the wav to mp3/aac/etc and syncs perfeclty.

The target length is of the entire audio track, not of selection, which is what I want.

This is a rather lengthy example, but hopefully will illustrate clearly the technique. You will probably find quicker ways once you’ve got the hang of it.
Using the image in this post as an example: Sync one audio track to another by 2 points

  1. With the Time Shift Tool, drag the second to the right so that the first marked peak in track B lines up with the first marked peak in track A. Zoom in as necessary to align them precisely (I use “Ctrl + Mouse Wheel” for zooming, but whatever method you find easiest: Zooming Overview - Audacity Manual)
  2. Select from the first marked peak in track A to the second marked peak in track A
    (see: Selecting Audio - Audacity Manual). Again, use Zoom as necessary to make the selection as precise as possible.
  3. Set the Selection Toolbar (Selection Toolbar - Audacity Manual) to show “Start and Length of selection”.
  4. Set the Selection Toolbar to show “hh:mm:ss + milliseconds” or “hh:mm:ss + samples” (the latter is the most accurate).
  5. Make a note of the “Length” of the selection.
  6. Select from the first marked peak in track B to the second marked peak in track B.
  7. Open the “Change Tempo” or “Change Speed” (whichever suits your needs - see here if you are not sure what the difference is: Index of Effects, Generators, Analyzers and Tools - Audacity Manual)
  8. Enter the length that you noted in step 5 as the new length, and click “OK”.
  9. Check that the second marked peak in track B lines up with the second marked peak in track A.
  10. “Ctrl + Z” to Undo the effect.
  11. “Shift + K” to extend the selection to the end of the track (or “Select menu > Region > Cursor to track end”)
  12. “Ctrl + R” to repeat the last effect.