Synchronizing Sound and Video

When capturing or downloading video from the internet you may occasionally find inaccurate sound and video synchronization in captured movies.

Most Common Problems that Occur are:

  • The sound is offset by the same amount throughout the movie file.
  • When capturing a long movie, the sound and video synchronization can be good at the start of the video, but the further one goes, the more the sound and video synchronization becomes a problem. In this case the scale of the video and sound is different and is a known problem in Quicktime.

When Do Synchronization Problems Occur?

The problem of the gradual drift is most likely to occur when the pause/resume button in the capture window is not used for extended periods of capture. These buttons start a new video file each time they are used, so they can re-synchronize the video and sound. This is less common as the capture window breaks the files up in 5 second chunks. But, video might be acquired from other sources that exhibit the problem. Using the procedures below may not be very useful in this situation, since there are variable length sections of video and sound and synchronization in one area may lead to slight miss alignment in others. Fortunately, the contracting and expanding procedures work best for movies created when the pause/resume button are not used because any drift is constant across a single movie file.

In the main menu bar select Edit > Equalize track times. This can only be done after the movie capture. However, it is not as accurate as equalizing during capture if your movie is made from more than one file. You can choose to make the equalization permanent if your movie is attached to a timeline window. This procedure stretches or contracts the length of the sound track to equal the length of the video track. This feature is also useful for resetting the tracks when you have nudged, expanded, or contracted the sound track and lost a synchronization point altogether.

A. Synchronization of audio that is offset the same amount throughout a movie.

  • movie resource, so the change is permanent.
  • and resume play. If the video is attached to a timeline then SportsCode will try to update the
  • When you use these features the video and sound will pause, move in the direction specified
  • down the keys to repeat the nudge continuously.
  • (CONTROL+OPTION+COMMAND+R). This nudges the sound track one frame to the right. Hold
  • If the sound is slightly behind the video, select Edit > Nudge sound track right
  • down the keys to repeat the nudge continuously.
  • (CONTROL+OPTION+COMMAND+L). This nudges the sound track one frame to the left. Hold
  • If the sound is slightly ahead of the video, select Edit > Nudge sound track left
  • Zoom in the timeline, turn on movie looping and play the timeline movie.
  • Move the timeline cursor to a section in the movie, near the start of the movie that can be used to evaluate the synchronization.
  • Save timeline.

B. Synchronization of audio that is gradually drifting throughout a movie.

  • Move the timeline cursor to a point near the end of the movie.
  • Zoom in the timeline, turn on movie looping and play the timeline movie.
  • If the sound is slightly behind the video, select Edit > Contract sound track
  • (OPTION+COMMAND+L).
  • If the sound is slightly ahead the video, select Edit >Expand sound track (OPTION+COMMAND+R).
  • When you use these features the video and sound will pause, move in the direction specified and resume play. If the video is attached to a timeline then SportsCode will try to update the movie resource, so the change is permanent.
  • Save timeline.

Note: The anchor point for contracting and expanding the sound track is the beginning of the sound track at the start of the movie. Contracting and expanding acts on the whole length of sound track.

Reset the sound and video tracks by choosing Edit > Equalize track times.

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