Convert MP3 from Mono to Stereo Using Lame – How to Guide

lamemonomp3stereo

An application requires that the mp3 files it receives are encoded with 2 channels (stereo), but the original files have only 1 channel (mono).
We use Lame for conversion, but i fail to make it clone the mono channel and create a fake stereo.

lame.exe -m j mono.mp3 stereo.mp3

-m d or -m s doesn't seem to work either. Is it possible to do this with lame?

Best Answer

The answer to my own question is: No - it is not possible with lame

My work-around solution is to use the command-line tool sox and do the channel duplication prior to mp3-conversion:

sox mono.wav -c 2 stereo.wav

Then afterwards use lame:

lame -m j stereo.wav stereo.mp3

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Converting .wav (CCITT A-Law format) to .mp3 using LAME

You want to use SoX to convert the A-law input data to a more standard PCM data for LAME to process.

sox -A -c 1 -r 8000 input.8khz-mono-alaw.wav ouput.wav

Now output.wav should contain standard PCM WAV data. Run your LAME command on this (add whatever options you like):

lame output.wav output.mp3

Or, pipe the SoX output into LAME directly:

sox -A -c 1 -r 8000 input.8khz-mono-alaw.wav - | lame - output.mp3

Windows – How to force a stereo microphone to mono in software (W7)

I don't think Windows offers such a feature. You can solve this by using software that simulates virtual audio devices and cables. I use Voicemeeter (http://vb-audio.pagesperso-orange.fr/Voicemeeter/index.htm) and it works (same situation - external audio interface + XLR mic). There are some alternatives as well. Search for "windows virtual audio".

How to for Voicemeeter: In Voicemeeter assign the XLR stereo input to an input. Toggle 'mono' button. In programs like Skype use Voicemeeter Virtual Output as input device.

Best Answer

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Converting .wav (CCITT A-Law format) to .mp3 using LAME

Windows – How to force a stereo microphone to mono in software (W7)

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