Subtitle: A better way to replace your camcorder’s audio signal with HQ audio recorded separately

Software needed: Logic Pro 9, MPEG Streamclip (freeware) – optional

We’ve all been there. Having our concerts recorded with a video camera while, on most occasions, recording audio separately with a portable device such as Zoom H4n due to awful sound quality most consumer video cameras possess. Alternatively, you may have recorded music in a recording studio and have done some video footage along the way, wanting to combine the two afterwards.

So how do we go about the process of replacing the camcorders’s audio signal with the HQ, separately recorded, audio?

Until recently, I was doing this using several steps and utilizing apps from Logic Pro 9, Soundtrack Pro, iMovie and MPEG Streamclip, explained in this article. Although this approach does the job just as well, it’s somewhat impractical as it takes ages for iMovie to encode and import/export videos while also occupying a large amount of space on your hard drive.

A few days ago, however, I discovered a much faster technique for this task thanks to Logic Pro 9‘s replace audio to video function. This process is very simple and takes seconds to complete, just follow this step-by-step guide:

1. Open the audio file in Logic 9 and make sure it sounds good – add any necessary EQ, compression, reverb, fades etc.

2. Go to File > Open movie and select the video file of your choice. Now, go to File > Import Audio from Movie . This will import the camcorder’s audio for easier synchronization.

3. Zoom in both audio tracks and align the good audio to match the camcorder’s audio perfectly (see the image below). If you’ve done the job well enough, you should be able to hear two audio signals simultaneously with no delay between them. Make sure to MUTE the camcorder’s audio at this point.

4. Go to File > Export Audio to Movie. When a window pops up, remember to deselect the audio file from the menu so that you’ll only hear the good audio signal in the exported movie.

That’s it! Logic will now bounce the audio track and create a new video file. If you need to trim the video or export several smaller video files for YouTube, I recommend using MPEG Streamclip (freeware). For some tips on using MPEG Streamclip, read my Synchronizing audio/video article part 1. Digging deeper into this app, you’ll find it’s even possible to copy two or more different clips of a movie, join them and export them as a single video file, all in one step – just select In and Out for the chosen clip, select Edit > Trim and then Edit > Copy. At this point just click Edit > Undo and paste the clip wherever you want to.

The settings I usually set when exporting video for YouTube are the following: File type (Export to MPEG-4): .mp4, compression: h264, quality: 100%, limit data range: 5000 Kbps.

If you find this tutorial too complicated, don’t have access to Logic Pro 9 or are a Windows user, I’d recommend checking DualEyes – an application for both OSX and Windows that retails for $149 and does the whole process of replacing audio of a video file automatically for you, even several files at once.

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