How do I create a seamless loop of audio?

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How do I create a seamless loop of audio?

Permanent link to this post Posted by Smoo » Sun Jan 27, 2008 9:02 pm

Greetings!

I'm trying to loop a several-second sample of an instrument tone so that I can play indefinitely do simulate a note being played, for however long the user wants. I'm trying to create virtual musical instruments with Second Life. Problem is, I cannot get a sound to loop cleanly. No matter what I do, I end up with a click or popping noise.

I've crossfaded, tried reversing the sound on itself after it ends to create a seamless transition, I've tried other file formats and bitrates... no matter what I do I cannot achieve a smooth-sounding loop. It seems like this should be rather simple.

What am I doing wrong? Is there any sort of plugin that can find an identical point in the sound at which I can trim the sound and thereby achieve a smooth loop?

I hope someone can help me. This is driving me nuts!

Thanks in advance for any help.
Smoo
 
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Re: How do I create a seamless loop of audio?

Permanent link to this post Posted by kozikowski » Mon Jan 28, 2008 12:35 am

<<<I hope someone can help me.>>>

Certainly. No trouble at all.

Since all actual looping methods create some sort of disturbance at the loop point (sometimes changing with the humidity) the solution is to avoid looping. Create a musical piece of a half-hour or so with several copies of that one clip seamlessly edited one after the other. Play the piece, copy and paste that clip to the end creating two. Copy the two and paste to get four, etc. Export that as a final music file. Pick a length of final show that nobody is likely to exceed.

That's how the fronts of DVDs are done. Everybody always wants to know how to make a DVD intro loop cleanly. You don't. Just make the DVD intro fifteen minutes long even if you have to repeat a short one yourself several times before exporting one long file.

Koz
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Re: How do I create a seamless loop of audio?

Permanent link to this post Posted by Smoo » Mon Jan 28, 2008 11:44 am

Thanks for the reply.

I'm actually trying to loop a clip under ten seconds in length. I noticed that if I add a new stereo channel, paste the same track to that channel, align it to start when the first one ends, and cross-fade in and out, I can blend the two together. The problem is doing this in a looping format...

Any advice for creating a smooth loop in a very short file?

Thanks again!
Smoo
 
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Re: How do I create a seamless loop of audio?

Permanent link to this post Posted by steve » Mon Jan 28, 2008 12:13 pm

This works on Windows, and should be similar on a Mac.

Download and install Audacity 1.3.4 (install in a different directory to v.1.26)

Import the audio sample that you want to loop
Zoom in very close somewhere in the middle of the audio clip so that you can see the individual samples.
Place the cursor at a point where the waveform crosses the "0.0" line, left click and drag a little to the right.
Now zoom out to see the whole wave
Hold the shift key down and click on the right hand side of the wave form and drag to line up the selected region with the end of the track.
Click on "Edit->Split New"

Lets call the top (left hand side) audio "Sample A" and the lower (right hand side) track "Sample B"

Use the "Time shift tool" to move Sample B to the left and sample A to the right.
Edit them so that there is a click free join between the two (use a short cross fade or something similar).

Export the audio and you will have a sample that will loop seamlessly.

Note 1: Do not Export as MP3 as it is impossible to make them loop without a glitch. MP3's contain a short silent "lead in" before the sound starts.

Note 2: This loop will start playing from the middle. If you need it to start at what was the original beginning, repeat the whole process so that it starts in the correct place.
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Re: How do I create a seamless loop of audio?

Permanent link to this post Posted by kozikowski » Mon Jan 28, 2008 5:35 pm

As I understand the problem, it's creating a clip that somebody else can loop.

Client side looping has never worked reliably as far as I know. Good to know the technique in 1.3.4.

Koz
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Re: How do I create a seamless loop of audio?

Permanent link to this post Posted by Smoo » Mon Jan 28, 2008 9:39 pm

Stevethefiddle,

Thank you very much for your assistance. Your instructions were exactly what I needed!

I have a two-second musical note that, using your directions, I have looping perfectly. It's a bit tricky getting the fade to sound perfect, but I'm figuring it out. Not a problem.

I uploaded the sound to Second Life and it loops perfectly as I originally intended. I'll now be able to accomplish my aim.

Thank you again for your advice! :mrgreen:
Smoo
 
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