Synchronize Flv Audio & Video

Computer video files, unlike traditional film, store the audio and video components separately, which can lead to synchronization problems.

FLV files are video files that can be played using the Adobe Flash browser plug-in. Because Flash is ubiquitous, FLV is the principal format for videos on popular websites like YouTube, MySpace and Google Video. If you download an FLV video from one of these websites, you may encounter audio/video synchronization problems when you play the file back locally. To see the video correctly, you can either use playback software with audio synchronization features, or permanently repair the synchronization using editing software.



1. Download and install the VLC media player (see Resources).

2. Launch VLC from your Start menu or the desktop.

3. Choose the “Open File…” command from the “Media” menu. In the dialog that appears, find and select the FLV file with synchronization problems, then click “Open.” The video will begin playing.

4. Press the “J” and “K” keys to shift the audio track backward or forward in time, respectively, relative to the video track in 50 millisecond increments. The shifts will be affected on the fly, with a text overlay appearing to indicate the current audio delay value as a positive or negative number.

5. Fine tune the synchronization by selecting “Track Synchronization” from the “Tools” menu. In the “Adjustments and Effects” window that appears, input a more precise value to the “Advance of audio over video:” field. These adjustments also take effect immediately. You can now view the video with correct audio/video synchronization, adjusting as necessary for further errors as playback continues.

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Media Player Classic Home Cinema

6. Download and install Media Player Classic Home Cinema (see Resources).

7. Launch Media Player Classic Home Cinema from your Start menu or the desktop.

8. Click the “File” menu, then choose the “Quick Open File…” command. In the dialog that appears, find and select the FLV file and click “Open.” The video starts playing. Watch the video briefly to determine whether the audio track is playing back ahead of (before) or behind (after) the video track.

9. Choose the “Options…” item from the “View” menu or press the “O” key to open the “Options” window. Click the “Audio Switcher” item in the “Internal Filters” group in the list on the left side of the window. The “Audio Switcher” controls are revealed in the right pane.

10. Enable the “Audio time shift” checkbox, and input a millisecond value into the corresponding field. If the audio is playing before the video, use a positive value, and if the audio is playing after the video, use a negative value. Click “Apply,” watch the video a bit more to see the effect of your adjustment, then change the value again, repeating the process until the synchronization is correct. You can apply adjustments as necessary while you watch if new problems emerge.


11. Download and install Avidemux (see Resources).

12. Launch Avidemux from your Start menu or the desktop.

13. Click the blue folder icon in the top left corner of the Avidemux window, or choose “Open…” from the “File” menu, then find and select the FLV file and click “Open.” One or more dialog boxes about codec options may appear, depending on the type of FLV file you’re working with. Simply click the “Yes” or “OK” button on each, and the video will appear in the middle of the window. You can play it back using the blue buttons near the bottom of the window.

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14. Enable the “Shift:” checkbox, then enter a positive or negative millisecond value into the corresponding field to shift the audio forward or backward in time, respectively. The simplest way to determine the correct value is to use one of the two playback programs described in the first two sections.

15. Choose “FLV” from the “Format” drop-down menu, then click the disk icon at the top of the window or press “Ctrl-S” to save your file. Select a name and location for your file, then click “Save.” A dialog appears to show the progress of the file’s creation, and a message appears when the process is complete. You can now play the FLV file you saved with its adjusted synchronization.