Unlocking iMovie '09 & '11
There is a reason that documentaries will cut away from an interview and show photos or other footage while the interviewee's voice continues over top the alternative footage. (The alternative footage in this case is often called the B-roll.) This is a great film-making technique. Who wants to stare at the same person sitting still in a chair for five minutes, even if they are saying something really important? You see the same thing happening in newscasts. Most sports guys are not exactly handsome, and their ridiculously colored sport coats are even worse. It's much better that we can watch the footage of the high school football game while the sports guy dazzles us with his voice instead of his jacket.
iMovie HD was up to this task. Exporting the audio from a video track was as easy as selecting a menu item. A common misconception is that iMovie '08 removed this feature. It's still there, but like everything else in the new iMovie, it's different, and in this case even a little better.
Although this wasn't on my list for the week, there has been a lot of demand for a How To on this feature. Here is how you extract audio from a video clip.
A rose by any other name
Everyone who was used to extracting audio from a clip probably went to the iMovie '08 help documentation and searched for the term, "extract audio." It didn't turn up. And so, many reasonably assumed that it can no longer be done. But it can. Apple just decided not to call it "extracting audio". There are some who say they found a description of the feature in the help documentation, but I have had no such luck. (An incredibly helpful Apple Support Specialist hooked me up with an explanation of how it works.) Whatever Apple calls it now, I am still calling it "extract audio".
Double the fun
This feature requires a little bit of planning. That's because you can't easily extract the audio from a clip that you've already added to your project. Instead, you can only extract it from a clip in the Event Browser. The easiest way to manage this is to plan on dragging a clip into your project twice. Here is a sample walk-through of the process.
First I select a range of video in my Event Browser and drag it to my project. In my project window, it will look something like this:
The range I selected in the Event Browser should still have the yellow (but now appearing gray) line around it. Taking care not to lose that selection by clicking somewhere else, I drag the exact same clip to the project, but this time I am holding down the Command (Apple) and Shift keys. I drop it at the beginning of the corresponding clip in the project window, making sure to hold those two keys until after I let go of the mouse. Now, just the audio from the clip has been added, represented by a little green flag below the video clip.
There's always a catch
I could stop there and all of you would know everything about extracting audio. But, there are some oddities about working with extracted audio, or any audio for that matter, that I feel compelled to point out.
Some of you may find yourselves wanting to come back from your B-roll footage to the original video, just like you might do in a newscast by coming back to your newscaster. This means that you need to make sure that whatever middle footage you remove from your A-roll perfectly matches the length of the B-roll footage you insert. If you don't do this, your audio will be out of sync when you come back to your A-roll.
The easiest way to do this would be to split your audio so you can match the pieces of audio and video together. Unfortunately, you can't split an audio track in iMovie '08, only shorten and lengthen it. You could deal with this alternatively by only dragging from the Event Browser the audio that corresponds with the B-roll. It would look something like this: Drag in the A-roll footage; add your B-roll footage drop in the corresponding extracted audio; drag in more A-roll footage. This will work fine as long as you pay attention to select the proper ranges in the clips in your Event Browser. If you are having trouble selecting the clips with accuracy, go read the post I made about frame-precise edits.
How to make frame-precise edits
But what if you want insert B-roll footage while working inside the project window? Let me show you something to watch out for. If I select the range I want to delete, it looks like this:
Notice that I have a total of 15 seconds of video and 15 seconds of corresponding audio. I can also tell how much I have selected if I look at the bottom of my project:
This is telling me that I will need to come up with 2.2 seconds of B-roll to replace the clip I am deleting. When I actually hit the delete key, the selected video is deleted, and I am left with this:
Here is where an oddity (well, actually a bug) pops up. I should have about 13 seconds of video and 13 seconds of audio. The audio track--the little green flag--actually says I have 15 seconds of audio, even though the track is finishing at the same time as my 13 seconds of video. Maybe the 15 seconds will show up when I drop in the right amount of B-roll footage?
No! The audio clip really was only 13 seconds! It got shortened by a new "feature" that automatically cuts all audio to end with the last video clip. Adding enough footage after the fact doesn't restore the lost audio. I can fix this problem by just dragging out the end of my audio clip, but I can avoid it all together by taking another approach.
More Planning Ahead
Before I delete any of the A-roll footage, this time I will add in the B-roll footage I want at the end of the project.
This is actually a wise practice anyway, because usually if you go to a B-roll, there is something of a specific length that you want to show, so why not begin with adding it to your project? Notice that the extracted audio ends before my B-roll clip starts. (This B-roll is actually just a photo I added.)
Carrying on, I select a range of the A-roll for deletion that is the same length as my B-roll footage. I go ahead and delete it, and you will notice that the B-roll footage at the end preserved the length of my extracted audio.
I move my B-roll footage to the middle where my A-roll was deleted, and I get this:
The full 15 seconds of extracted audio was preserved. All that remains to to mute the audio on the A-roll video, so that you don't have two tracks playing the same audio. Just select the clip you want muted and open the Audio Adjustments window. The button looks like this:
And the window looks like this:
Reduce the volume for that clip to zero, just like I did in this window. Leaving this window open, select the other A-roll clips that need muting and do the same thing. Your final project window should look something like this:
Notice how my A-roll clips have a muted speaker icon on them. (That icon on my B-roll footage is actually telling me that it is a picture, not video. Pictures don't have audio, hence no speaker icon.)
Let's be precise about it
You may have now noticed a hitch in my description of the process. Even if you replace 2.2 seconds of A-roll with 2.2 seconds of B-roll, your audio sync could still be off by a tiny bit. This is because with video, there are anywhere from 2.5 to 3 frames of video (depending on your format) per tenth of a second. Even if you measured out 2.2 seconds of B-roll, you could still be 1 to 2 frames out of sync. How can you repair this accurately?
Again, an incredibly helpful person at Apple helped me out with this one. If you have a clip selected, choose "Trim..." from the Edit menu.
This shows the original source footage in the project window and gives you the opportunity to basically reselect the video you added to your project.
For the really cool trick, hover your mouse over the edge you want to extend or shorten and. while holding down the Shift key, use your left or right arrow key to bump the selection left or right by one frame. If you were just barely off on your sync before, one or two key strokes should be sufficient.
The same trim trick works for the extracted audio. If you want to make adjustments to that, select "Trim..." from the Edit menu again. You will see the source video in your project view again, but it will appear as a waveform. Reselect the range you need and click done. You should now have a well synced A to B to A sequence, with A-roll audio running throughout.
The best laid plans
So planning really is key to using extracted audio efficiently. In some ways I like the new way better, but this has more to do with the way iMovie edits by reference rather than making changes to the actual clips. In the old days, if you deleted your extracted audio, you had to make sure you were quick to undo your mistakes. That clip was all you had, absent reimporting the video you were using. This new way is much more forgiving. However, this forgiving nature is necessary, considering the clumsiness of the tools you have to use to edit audio. All in all, you can get the same results as before, so we can be grateful this functionality didn't really get the axe.