Variable tempo change?

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Variable tempo change?

Permanent link to this post Posted by JayH1119 » Sat Mar 04, 2017 10:50 pm

I've been mixing tracks of live recordings that come from different sources (e.g. soundboard, mic and portable setup 1, mic and portable setup 2, etc.) Most of the time, in order to synchronize the sound, it is sufficient to align the beginning of the tracks and then change the tempo of one so that the end of the tracks align. I have recently come across a reference sources that seems to change its tempo mid-track. I can align the beginning and end as already stated but the track being synchronized will speed past the reference and then come back in sync at the end. (I suspect this is due to ad-hoc mastering of the reference source on the fly...)

What I 'm envisioning is a tool that will allow me to mark a number of corresponding points at various times in the tracks being synchronized and have a tempo and/or pitch change performed automatically between all those marks.

Thanks in advance for any help.
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Re: Variable tempo change?

Permanent link to this post Posted by Gale Andrews » Sun Mar 05, 2017 2:21 pm

What version of Audacity do you have?

Does the pitch change with the tempo change? If so the most flexible tool is Time Tracks that works by using envelope points to mark the pitch/tempo change. Or in Audacity 2.1.2, Change Speed - also affecting both tempo and pitch - lets you set a speed change based on length.

If the pitch needs to be kept constant, you can use Sliding Time Scale / Pitch Shift in sections of audio and don't change the pitch, only the tempo. If initial and final tempo are set the same, then it gives a constant tempo change throughout.


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Re: Variable tempo change?

Permanent link to this post Posted by JayH1119 » Sun Mar 05, 2017 7:03 pm

I'm working in 2.1.2.

I have used the effects you mention but they only work by applying the same factor of change across the entire selection. I have been splitting the clips into 1 minute sections, aligning the beginning and using the Change Tempo tool to align the end of the section and it works adequately but very time consuming. I was hoping to be able to graphically represent multiple corresponding points between tracks across a single selection and have the tool change the temp individually between all of those marks.
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Re: Variable tempo change?

Permanent link to this post Posted by JayH1119 » Sun Mar 05, 2017 7:40 pm

The time track idea might work if I could apply it to just one track and see the change in the wave form real-time. Remember I have a reference track that I'm trying to synchronize a track with variable tempo changes to.
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Re: Variable tempo change?

Permanent link to this post Posted by Gale Andrews » Sun Mar 05, 2017 8:10 pm

JayH1119 wrote:I have used the effects you mention but they only work by applying the same factor of change across the entire selection.

Sliding Time Scale > Pitch Shift can set a different starting and ending tempo or pitch change.

JayH1119 wrote:The time track idea might work if I could apply it to just one track and see the change in the wave form real-time. Remember I have a reference track that I'm trying to synchronize a track with variable tempo changes to.

OK. If you don't want to hear the reference track being modified, you can mute that track.

To apply Time Track to one track only, click above Mute/Solo to select that track, then Tracks > Mix and Render. Remove Time Track to hear the result.


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Re: Variable tempo change?

Permanent link to this post Posted by JayH1119 » Sun Mar 05, 2017 9:19 pm

hmmm, I appreciate your help Gale but I think I'm not explaining the problem correctly.

I have a soundboard source and an audience source of the same live concert. Each song is its own track. I load the first song's soundboard track and line it up with the first songs audience track at the beginning of the song. I go to the end of the tracks, determine how far off the one is from the other and apply a Change Tempo so the end's line up. Now I have the beginnings aligned and the endings aligned but over the course of the song the tracks vary from one another by varying amounts. For example:

If I apply the same exact process described above to the first quarter of the tracks, it might take a .028% tempo change to get things lined up, but the next quarter of the tracks might take a -.049% tempo change to have things lined up, and the next quarter yet another, etc.

So, the pitch/tempo changes continually throughout the track. one setting at the start and one at the end won't do it.

The end result is the mixing of both tracks together. I need to hear the reference track unmodified along with the track I'm warping. The time track is really kinda weird too - It isn't granular enough, ever with a minimum of 99% and a maximum of 101%, to effect the changes in tempo I need. I can't seem to delete a point once its in place, no dialog to specify exact settings, only a visual approximation of values...
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Re: Variable tempo change?

Permanent link to this post Posted by Gale Andrews » Mon Mar 06, 2017 3:05 am

JayH1119 wrote:Change Tempo so the end's line up.

Change Tempo in 2.1.2 is unsuitable for aligning. That is why I did not mention it. Please see http://manual.audacityteam.org/man/change_tempo.html#Limitations. In the next version of Audacity, Change Tempo can work round that by selecting a new "high quality" option.

JayH1119 wrote:Now I have the beginnings aligned and the endings aligned but over the course of the song the tracks vary from one another by varying amounts. For example:

If I apply the same exact process described above to the first quarter of the tracks, it might take a .028% tempo change to get things lined up, but the next quarter of the tracks might take a -.049% tempo change to have things lined up, and the next quarter yet another, etc.

So, the pitch/tempo changes continually throughout the track. one setting at the start and one at the end won't do it.

The end result is the mixing of both tracks together. I need to hear the reference track unmodified along with the track I'm warping.

The rule in Audacity is to select the tracks you want to apply an effect to. This applies to Mix and Render too. Unselected tracks won't be modified.

After rendering a time track, remove the Time Track, so that it does not affect the reference track.

JayH1119 wrote:The time track is really kinda weird too - It isn't granular enough, ever with a minimum of 99% and a maximum of 101%, to effect the changes in tempo I need.

Have you tried dragging the Time Track window down by its bottom edge so you can see the vertical scale (Choosing Linear Scale in the Time Track menu will probably be better). But it looks like the minimum change is by 0.1 % (just by observation).

JayH1119 wrote: I can't seem to delete a point once its in place

Drag the envelope point out of the Time Track in any direction.

Have you decided if you want to change pitch with tempo? If you do, then Change Speed is an accurate option because you can specify the length in the "New Length" box. The effect may not be sample accurate in all cases in 2.1.2, but it will be accurate to the nearest sample in the upcoming 2.1.3 release if you want to try an unfinished testing build of that.



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Re: Variable tempo change?

Permanent link to this post Posted by JayH1119 » Mon Mar 06, 2017 5:06 pm

Gale Andrews wrote:Change Tempo in 2.1.2 is unsuitable for aligning. That is why I did not mention it. Please see http://manual.audacityteam.org/man/change_tempo.html#Limitations. In the next version of Audacity, Change Tempo can work round that by selecting a new "high quality" option.


OK. I had tried it on a few previous projects and the results were quite acceptable, even over stretches of an hour to an hour and a half. As I am not trying to change pitch, I will take a look at Sliding Time Scale for those tracks with a linear delta.


The rule in Audacity is to select the tracks you want to apply an effect to. This applies to Mix and Render too. Unselected tracks won't be modified.

After rendering a time track, remove the Time Track, so that it does not affect the reference track.


I had seen the below under Time Tracks in the audacity manual and assumed that the default behavior of having an effect applied to only the highlighted audio was not the case.

Image


Have you tried dragging the Time Track window down by its bottom edge so you can see the vertical scale (Choosing Linear Scale in the Time Track menu will probably be better). But it looks like the minimum change is by 0.1 % (just by observation).


I had not tried that as my screen space is a little limited, especially as I like to have large fonts, etc for my older eyes :) As noted, 0.1% will not be granular enough but I'll take another look at it and see if I can get it to work.


Drag the envelope point out of the Time Track in any direction.

Have you decided if you want to change pitch with tempo? If you do, then Change Speed is an accurate option because you can specify the length in the "New Length" box. The effect may not be sample accurate in all cases in 2.1.2, but it will be accurate to the nearest sample in the upcoming 2.1.3 release if you want to try an unfinished testing build of that.


Thank you. Perhaps the high quality option of Change Tempo will be helpful.
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Re: Variable tempo change?

Permanent link to this post Posted by Gale Andrews » Tue Mar 07, 2017 2:34 pm

JayH1119 wrote:
Gale Andrews wrote:The rule in Audacity is to select the tracks you want to apply an effect to. This applies to Mix and Render too. Unselected tracks won't be modified.

After rendering a time track, remove the Time Track, so that it does not affect the reference track.


I had seen the below under Time Tracks in the audacity manual and assumed that the default behavior of having an effect applied to only the highlighted audio was not the case.
Image

Time Track does indeed apply to all tracks, hence when listening during playback you have to mute the tracks on which you don't want to hear the effect.

Time Track does apply to all tracks when exporting, unless you mute tracks you don't want to export, or only select certain tracks then use Export Selected Audio.

However as I understand it you wanted to see the result in the waveform, and only for particular tracks. In that case Mix and Render on selected tracks then remove the Time Track is the answer, and is not breaking any rules. Because Time Track does apply to all tracks, Render of selected tracks then remove the Time Track is also the only way to export a file with all tracks present but with Time Track only applied to some tracks.

JayH1119 wrote:Perhaps the high quality option of Change Tempo will be helpful.

If you want to try that testing build, it's here: https://www.fosshub.com/Audacity-devel.html/. Just be sure not to hand edit any AUP file you save. RC2 is not safe for doing that.


Gale
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Re: Variable tempo change?

Permanent link to this post Posted by JayH1119 » Thu Mar 09, 2017 11:30 pm

Thanks Gale. I have been able to effect the change I wanted using the time track, although I think my original suggestion for the interface would make it a LOT easier :D and quicker.

Your patience and help is appreciated
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