Change Tempo Visually Using Waveform

[Gale Andrews]

Split from http://forum.audacityteam.org/viewtopic.php?t=92188

Side note: It would be nice if we could match tempos of multiple tracks by matching the first beats of two different songs, then simply use the mouse to drag the end of the track in or out until the last beat matches.

Yes that would be nice, but is difficult to do. It's a fairly common feature request, though for some reason I don't see it listed on our feature request page.

What's there is:

• More region/clip dragging functionality:
  
  • Time Stretching: (7 votes) mouse tools for both pitch-variable and pitch-constant time stretching. Adobe Audition has this and it's vital for the production of sample-based music.

And I am sitting on these requests which I have not added yet:

• Drag track boundaries to change tempo without pitch change (9 votes):
  Pointing/dragging, change the speed of certain part of the sound track. It is a bit like
  Effect>Change Tempo, but instead of of selecting a section of sound track
  and go Effect>Change Tempo... with such feature/tool, I can then drag
  certain point of track forward/backward so that certain part of the track
  speed up/slow down and have my dragged point to sync with a precise time
  mark. This is a really useful feature/tool to have if I want to sync >multiple
  parallel tracks and they have slightly different tempo.
• Elastic Audio quantisation - drag clip boundaries to match beats (3 votes)

Is the drag to quantise regarded as the same as drag to change tempo?


Gale

[steve]

Is the drag to quantise regarded as the same as drag to change tempo?

I'd think not. Tempo quantization has the additional requirement of snapping to beats.

[Fluidstream]

This is something I brought up in a recent post to the Windows forum. It's about adjusting the tempo of music. It usually takes me 15-20 attempts to get exactly the right percentage down to the thousands of a percent using Tempo Change. Rather than using trial and error to match beats with Tempo Change, it seems much simpler, from a user standpoint, to be able to match the first beats of two songs, then go to the end of the shorter song, then click and drag the longer song to compress or stretch it as needed to match the beats visually. That could get the beat-matching done in one step rather than 15-20 trial-and-error steps. I've been told that's difficult to program, but it was suggested that I add the request here anyway.

Thank you for such an amazing program which I've had for a long time, but I'm only now beginning to really delve into with things more complex than just recording, normalizing and whatnot.

[Gale Andrews]

I made a note then that you want to vote for "Elastic Audio quantisation".

Gale

[Robert J. H.]

This is something I brought up in a recent post to the Windows forum. It's about adjusting the tempo of music. It usually takes me 15-20 attempts to get exactly the right percentage down to the thousands of a percent using Tempo Change. Rather than using trial and error to match beats with Tempo Change, it seems much simpler, from a user standpoint, to be able to match the first beats of two songs, then go to the end of the shorter song, then click and drag the longer song to compress or stretch it as needed to match the beats visually. That could get the beat-matching done in one step rather than 15-20 trial-and-error steps. I've been told that's difficult to program, but it was suggested that I add the request here anyway.

Thank you for such an amazing program which I've had for a long time, but I'm only now beginning to really delve into with things more complex than just recording, normalizing and whatnot.

Why do you have to try a dozen times?
- align the first beat
- You know the length of a track that you want to sync with.
- Enter this length in the change tempo effect.

Ensure that you have the same amount of measures/beats, otherwise, it will be a two-pass task.
Robert

[Fluidstream]

Split from http://forum.audacityteam.org/viewtopic.php?t=92188

Side note: It would be nice if we could match tempos of multiple tracks by matching the first beats of two different songs, then simply use the mouse to drag the end of the track in or out until the last beat matches.

Yes that would be nice, but is difficult to do. It's a fairly common feature request, though for some reason I don't see it listed on our feature request page.

• Elastic Audio quantisation - drag clip boundaries to match beats (3 votes)

Is the drag to quantise regarded as the same as drag to change tempo?

Hmmm, I don't know. I'm not exactly sure what "quantise" means, but based on the descriptions that were posted, it seems like the same thing to me. If the beats are clearly visible in two different tracks, dragging the beats of one to match the other is all I'm looking for, though it could also be based on selections as well. I just ran into an issue today in which a song starts with some beats, then all the percussion disappears for a time, then the beats pick up again on a downbeat, which throws the last 3/4 of a song out of sync. It's not a big problem on this project because I'm slicing up four different remixes of one song and rearranging everything into one song that'll probably be 30 minutes long. Being able to select that non-percussive area, then shrink or expand it visually would be helpful, though I know it could be done with the sliding time scale with some trial and error. The visual method would just save anywhere from five to 30 minutes of work because it could be done in mere seconds.

I hope I didn't mess up the quoting attributions when I snipped.

I might also add that I've noticed the Sliding Time Scale feature does a massively better job of changing the tempo than just "Change Tempo", meaning the resulting quality is so much better. So if a visual method of tempo change makes it into Audacity, I'd be hurting the project if I didn't strongly recommend an "apply" button to finalize the tempo change with the Sliding Time Scale method of changing the tempo. I've already been told in the Windows forum that a more complex algorithm is used in Sliding Time Scale and the difference in quality is very positively noticeable. I can even see the difference visually when I zoom in.

[steve]

I'm not exactly sure what "quantise" means

In its general sense it means taking something that is continuously variable, and restricting it to discrete values.
Specific examples are:

• Taking an analog (or high bit-depth) signal, and "quantizing" the sample values to a restricted set of values.
• Taking a piece of music where the beats may or may not be aligned exactly with strict tempo, and stretching the audio so that the beats in the music match up with precise beat positions.

To expand a little on the second example, a fairly typical way that this is implemented is that the timeline is marked in bars and beats, and when audio is stretched, it snaps to positions where beats in the music match up with beats on the timeline. (There is often an amount of allowed "sloppiness" so that the "quantizing" is not too rigid). In more advanced (complex) implementations, one audio track may be stretched so that beats line up with a "tempo map" in which a changing tempo may be defined, or the snapping could be to adjust the beats of one audio track to match up with the beats of another audio track (essentially this is extracting a "tempo map" from the beats of one audio track, then "quantizing" the beats of the other audio track to the tempo map).

In its simplest form, you could define the tempo, which would show beats in a "timeline", then you can take an audio clip and drag to stretch, and the end that you are moving will snap to beat positions in the timeline.

[Gale Andrews]

I might also add that I've noticed the Sliding Time Scale feature does a massively better job of changing the tempo than just "Change Tempo", meaning the resulting quality is so much better. So if a visual method of tempo change makes it into Audacity, I'd be hurting the project if I didn't strongly recommend an "apply" button to finalize the tempo change with the Sliding Time Scale method of changing the tempo.

So would we have to decide whether the visual method used the SBSMS algorithm like Time Scale or the Soundtouch algorithm like Change Tempo, or would it do something else?

If Time Scale had length boxes like Change Tempo then as Robert said, you wouldn't need trial and error as now. But I think Time Scale needs a graph for those who are making "sliding" changes.


Gale