Reader Anonymous Colleague is having a one-sided affair with iMovie. He writes:
The Radio Shack lapel microphone attached to my camcorder produces left-channel-only audio. Do you know how to turn that into a standard mono audio track that plays through both channels?
I have the same issue when I record my share of Macworld videos . The microphone you refer to is mono and, like yours, mine records to only one channel. Although you could piece together an adapter that places audio on both channels, you can also fix it in post. I do it this way:
After I’ve completed my iMovie project I export it by choosing Share -> iTunes, choosing the Medium size option, and clicking Publish. This creates a 640x360 (or 480, depending on the aspect ratio) .m4v file. Open that file in QuickTime Pro and choose File -> Export. In the Save Exported File As dialog box that appears choose Movie to MPEG-4 from the Export pop-up menu and then click the Options button.
In the resulting MPEG-4 Export Setting dialog box choose Pass Through from the Video Format pop-up menu in the Video tab. Doing this tells QuickTime to leave the original video track alone. Now click the Audio tab. In that tab choose Mono from the Channels pop-up menu and click OK. Click Save in the Save Exported File dialog box and the file will retain its original video yet now bear a mono sound track that plays on both channels.
Ah, but what if all the audio in your movie is stereo except what you’ve recorded to your camcorder and you’d like to retain the movie’s stereo soundtrack? If you follow the steps above, the entire soundtrack will be in mono. In this case, you need to convert the camcorder material before it leaves iMovie.
You can do this in iMovie by Control-clicking on a hunk of video you’ve pulled from your camcorder and choosing Reveal In Finder from the contextual menu. The clip will appear in the Finder. Open it in QuickTime Pro and press Command-J to see its properties. Select Sound Track and click the Audio Settings tab. In the Channel Assignment column choose Mono for both channels from the Assignment pop-up menu and save the movie. Import this saved copy into iMovie and use it rather than the original.