Synchronisation Effects/Change Tempo

[Darcon64]

Windows 7; 64bit; Audacity Version 2.0.5 .exe.


Two music sources (about 180 seconds long):

#1 from a video in which the sound quality captured by the Canon EOS 6D is of poorish quality. Because the video was recorded at a disco, the DJ has altered the BPM from what was originally present to a higher number. The DJ does not know the (altered) BPM. The soundtrack is imported into Audacity and exported as an MP3 into a file to enable MixMeister determine its BPM (say 97.80)

#2 from a CD (the same song and version) imported into Audacity and exported to a file to enable MixMeister determine the BPM (say 94.80).

Using the Effects/Change Tempo facility, I do the conversion in the BPM window from 94.80 to 97.80; export the file as MP3 and determine the BPM with MixMeister. It's not quite 97.80. So, by experimenting by changing the 97.80 figure to various numbers around it, I finally get a BPM match to within 2 decimal places.

I now import that file below the the video version (#1 above) and near the beginning of the tracks, align them. For the first (say) 30 seconds, the tracks are in synch but then they drift out of synch.

It may be that MixMeister is not very accurate because at times, I get spurious results.

Is there a way to use the seconds/length facility (instead of the BPM facility). So, for example, if, using audio #2, I determine the distance ( in seconds) between to datum points and do the same for audio #1, how would that work?

Any other ideas appreciated.

[kozikowski]

Was he actually on 1200 Vinyl turntables? When the DJ pushes the speed control on those things, they drop crystal control. There is an internal setting where you adjust the free-run speed so it more or less matches the crystal control in the middle of the slider. Anywhere but the middle click, the rotation speed is sloppy and completely up to the DJ's hand and that muff he has jammed in his ear. That's probably why he can't tell you what the numbers were. That and he wasn't looking. If he was on fake 1200s, I wouldn't be surprised if the control was still analog and converted into control data sometime later, giving you the same effect.

That's the long way of saying it's probably going to wander no matter what you do and the best you can do is identify segments and correct them individually.

Why did you pick Effect > Change Tempo? Vinyl turntables change actual speed. Everything changes. And since they have to make some provision to mix and match turntables, I bet the "fake" 1200s do, too.

Koz

[steve]

The next version of Audacity (due for release in the next week or two) has an improved "Change Speed" effect that allows you to enter the length that you want to stretch to (and is very accurate).

[kozikowski]

(and is very accurate).

Does it do it on a ramp and can you control points in the middle if you have to? It's dynamic. These people are judging the floor and figuring out how fast they can match beats and segues so as not to be noticed.

You know the DJ is having a bad day when you hear the "finger on the record" effect.

I offer to get them something strong from the bar when that happens.

Koz

[steve]

You know the DJ is having a bad day when you hear the "finger on the record" effect.

When that happens you tell your sidekick to look after the show for a minute while you attend to a call of nature.
I think the American term is "passing the buck".

[kozikowski]

I've never seen an assistant DJ.

Here, take this violin for a minute. I have to go to the loo. The orchestra is at the andante, just there.

Koz