"B" roll

"B" roll is when you run different video over a sustained audio track from another cut. How do I put new video clips over a sustained audio track from a different video clip? Maybe another way of asking this is how do I extract the audio from one clip so that I can use it with different video clips? Do I set up different tracks for each video clip or do I put them all on the same track with the sustained audio I want to keep?

Sorry if this isn't clear. I don't know how else to ask this.

s.

I might be able to get you started on the solution. To extract the audio portion of a clip you can transcode it to an audio only format (I have done this by transcoding an mpeg4 to mp3). Then you can apply the mute audio effect on the clip upon which you wish to apply your "B" roll.

I think since version 0.7.4 you can separate the audio from the video. Then, if you put a video clip on an audio track, only the audio is used. There is no need to transcode or render to an audio clip.