How To Separate One Channel Audio To 2 Channels?

Question

Sometimes I stumble upon audio tracks and recently YouTube video clip where only one of 2 channels is heard. Is it possible to separate that 1 channel into 2 channels i.e left and right?

In case there is only left channel recorded, which makes natural splitting not feasible, can right channel be artificially generated or just mirrored from 1 channel making them both mono channels?

Solution

I'm assuming you have a stereo audio file where one channel is muted (no sound) and the other is not muted (has sound). Therefore you can only hear sound out of one speaker when played. You would like to duplicate the channel with sound so that you get sound out of both speakers.

can right channel be artificially generated

No. You can not make audio from nothing. If all you have is the left channel, where the original file has differing left and right channels, you can not generate the original right channel, and vice versa.

or just mirrored from 1 channel making them both mono channels

Yes. You can duplicate the channel that has sound, or convert to mono.^[1] This works best in cases where:

• There is little or no difference between the original left and right channels

Or:

• The original file only had one mono channel and at some point, an empty channel was introduced.

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Converting to mono

Just about any multi track/multi channel sound editor should be able to do this. I'll provide instructions for Audacity, because it's free. I'm using an old copy of Audacity 1.3.13, which is a beta version, but just about any version should have these options.

1. Load/open the audio file. You should see one channel with sound and one without (straight line).

   
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2. Click on the track name (drop down menu) and click Split Stereo to Mono. You could also just Split Stereo Track, but that would have the extra step of selecting Mono on the same menu of the track with sound (notice the greyed out options).

   
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3. Delete the track without sound using the little x to the left of the track name/drop down menu.

4. Export your file as your favourite audio format using the File > Export option. You may need to install additional codecs to export as some formats.

The reason we split and delete rather than just using built in convert to mono options is the built in convert to mono averages the two channels. When one channel has no sound, you end up with half the amplitude/volume on the final mono track.

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Duplicating the track and keeping it stereo

You could also copy the mono track, assign one as Left Channel and one as Right Channel using the name/drop down menu, select both and use the same menu to Make Stereo Track. This would give you a stereo track where the two channels are duplicates of each other.

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^[1]I recommend just using mono, since you will get the same sound out of both speakers with either method but mono can provide higher sound quality and/or lower file size with some lossy compression methods (such as MP3 discrete stereo, see the end of this page; joint stereo should be more or less the same quality of mono, since there is no difference between tracks).

Comments

[jakub.g]

related: superuser.com/q/351249/97570