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You are here: MacNN Forums > Enthusiast Zone > Art & Graphic Design > How to fix the problem of “sound is out of sync with the video”

How to fix the problem of “sound is out of sync with the video”
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May 28, 2006, 10:45 PM
The symptom: Your converted video begins with the sound and picture in sync. But over the course of the video, the audio and video slowly drift out of sync. The longer the file, the more out of sync the video and audio will be towards the end.

This is a very common problem and is usually the result of converting an MPEG4-based AVI file to a Mac-friendly video format.

There’s little I hate more than watching a video where the sound doesn’t match up with the mouths of the characters (especially when I’ve spent hours downloading or converting said AVI files). I’m here to offer a dirty, trial-and-error fix for this annoying predicament, but you’ll need QuickTime Pro and a little patience to do it.
You can download some useful software form here

Putting the Sound in Sync

Open your out-of-sync iPod video in QuickTime. Select Window: Show Movie Info and remember the FPS (frames per second) number. Close the info window.

Move the play head toward the end of the video and press play. Estimate how out of sync the audio is towards the end of the movie. Is it a second? Is it less than a second? If the words and audio are only slightly out of sync, you’re probably looking at less than half a second.

Now, select Edit: Select All. Your timeline is now completely selected. There are two handles on your timeline, one at the start of your movie and one at the end. Select the one at the end (it should turn black) and drag it all the way to the right to ensure that it is at the very end of the timeline.

We’re going to chop off a tiny part at the end of our movie in order to re-sync the audio with the video.

Use your left arrow key and count the taps it takes until the counter on the left goes down to the previous second. Each tap of the left arrow key rewinds one frame of video. How many taps did it take? Was it close to the FPS number? If it was, that means we just rewound nearly a full second of video. Tap the left arrow key until you’ve rewound the video to your estimate. Don’t worry; you don’t need to be exact. Just remember the number of taps you made and maybe write it down somewhere. Unless your audio is horribly out of sync, you’re probably not going to want to rewind more than 5 or 6 frames to begin with.

Okay, now select Edit: Copy, then Edit: Select All, then Edit: Add to selection & scale. Now, select Window: Show Movie Properties. You should see two video tracks and two sound tracks. Video Track 1 and Sound Track 1 are the original tracks. The second tracks are the slightly shortened tracks. Now, we’re going to mix-and-match using the check boxes to find out if we got closer to matching the audio and video.

When you begin, all four tracks will be selected.

Move the playhead to a point later in the movie and press play. Mix and match tracks labeled ‘1′ with tracks labeled ‘2′ selecting only one Video Track and one Sound Track at a time.

Mix and match the tracks to find the sweet spot.

Play Video Track 1 with Sound Track 2 and then try playing Video Track 2 with Sound Track 1. One of these options should be much better than the other. If you hit the sweet spot and the audio and video are matched up, delete the unselected tracks and select File: Save and make sure you select self contained movie. Your new QuickTime movie’s audio is now synced and it’s all ready for your iPod.

if the audio and video match up, delete the unselected tracks.

If one of the selections is only somewhat better than the original, close the file without saving it. When you reopen your original file, repeat the steps above, but you’ll tap the left arrow key a few more times than you did previously. A good rule of thumb is to progressively add five more frames than you entered previously.

Again select all, copy, add to selection and mix-and-match the tracks to see if you’ve come any closer.

If neither pairing is better than the way the original video was, you overshot the number of frames to trim. Repeat the process, but lower the number of frames that you tap with the left arrow key.

Above is a method to fix the sync problem. If you have any other iPod problems, you can refer here for more help. iPod Software Discussion Group ::
I wish it is useful to you; enjoy your favorite videos on iPod anytime and anywhere. :wavey:
( Last edited by ivan_best; Sep 28, 2006 at 05:23 AM. )
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May 29, 2006, 09:55 AM
Once upon a time I wrote an app specifically so you wouldn't have to do all that. Plus it's open source if you want to add to it in any way.

Sync Hole

Since then, someone went to RealBasic for a similar app. I don't know the mechanics of how it works, but I imagine it's the same mechanism, since it has similar limitations.

Movie Sync

Also, I honestly haven't had to use either of these for several years because 99.9% of downloads play correctly and in sync when I have the divx.com and insaneness.com components installed, and since DiVA keeps my own DVD rips in sync.
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