Getting Audio Channels in Phase

[BONSTER]

Hi,
I have been uploading videos to both Facebook and Youtube for some years without problem. Three weeks ago the audio started to come through garbled when video is played on mobile devices (android or ios). If you play the video on these devices using headphones or on a computer then audio works fine as you are hearing in stereo. If playing through the device loudspeaker audio is mono and garbled.

From what I have read in different forums the left and right audio channels are out of phase and need to be resync'd and advice is you can do this by:
- delete L-channel audio
- copy/paste R-channel to L-channel
- re-render (ie generate new file)
- re-upload file to YouTube

I have spoken to the provider of the videos who swears black and blue nothing has changed from his end to put the audio out of phase so I am left with trying the above fix.
My question for the forum however is can you do this using VLC and if so what are the steps. I have searched around and googled a bit on the issue but cannot find a definitive answer.

Thanks in advance,
Bonster

[Lotesdelere]

AFAIK VLC can't do that.
But you can use some dedicated audio tools like SoX or Audacity.

However, you don't need to delete one channel, just invert it.
And it is very strange that such a thing is happening. There is obviously an hardware and/or wiring problem somewhere.

[BONSTER]

Thanks for responding, look like I need to find a new video editing tool that can deal with the audio.