Audio in video problem

[didikai]

I have a video file where I only get audio from the left channel. I am not bothered about getting stereo audio and will be happy with mono.

I have Adobe Audition, but have not mastered it yet. After playing blindly with it I did manage to make a mono audio track to play on both channels and get it back into the video. The audio was in sync but part of it was missing.
Could someone give me step by step to fix this.
Many thanks

[redwudz]

I'm not clear on why part of it would be missing. Did you select the whole audio stream when you cloned it to the other channel?

I have only tried Audition a couple of times. I normally use the freeware Audacity. With it I create a new blank track, then select (All) of the old track, copy, then paste to the new blank track and save.