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If some clips are not synced during the automatic sync process, there are steps you can take to help them sync. If many clips are failing to synchronize, then use the suggestions listed below and make changes as needed.
Length of files. In general, PluralEyes 4 can automatically sync clips that include at least 5–10 seconds of good quality audio content. You may run into problems if you use audio clips that are short, like 3 seconds or less. Another possible issue is that audio clips which are short in length or have indistinct parts can make it difficult for the synchronization algorithm to find a match. This type of issue usually causes a small percentage of clips in a project to be unsynchronized. These can usually be corrected easily in your NLE editor. Check the files. Check whether the audio is of sufficient quality. PluralEyes 4 synchronizes clips by comparing their audio content only. PluralEyes cannot synchronize silent video, and does not use any clappers or timecode that might be present. You can try cleaning up the audio files in an external application, like Adobe Audition, and then reimporting them into PluralEyes.
First, check whether synchronization is actually possible. If there were periods of time in which only one device was recording, it is normal for the clips from that device to not automatically sync. Sometimes clips don’t sync because they are, in fact, not recordings of the same event, or they are recordings of different takes. It’s possible that you can sync the clips by hand, even approximately in your NLE editor by nudging the clips in the sequence into position.
Discontinuous clips are clips that are sequential but have some lost or dropped sound between them. This means the total time of the audio doesn't fully match up to the clips’ length. In order for PluralEyes to sync successfully, each clip must correspond to one continuous stretch of recording. That sound gap is going to confuse PluralEyes. However, PluralEyes 4 doesn't trim or edit your clips; it just syncs what is there. For details, see Preparing Files for the Sync. We normally don’t suggest editing your clips before using PluralEyes. However, in this case, you need to fix the problem by removing that sound gap. In your editing application, trim the discontinuous clips so all of the clips are continuous, and then add those clips back into PluralEyes 4. Then click the Synchronize button in the toolbar again.
If the sync of an audio clip to a video clip is good in the middle of the clip, but is a bit off at each end, then the most likely cause is that the audio recorder's recording speed was not perfectly accurate. This is called audio drift. PluralEyes 4 will detect this problem and fix it automatically by default. If you do not wish PluralEyes 4 to correct audio drift, you can go to the menu item Sync and uncheck the option Correct Audio Drift then restart the sync. When drift is detected in an audio clip, the sync is stopped. Drift correction is applied to all the audio clips on that track that need it and the sync is started from the beginning again. The drift correction process creates a new audio file for each original audio file. This new file is referenced when the project is exported.