This article outlines the most common causes of dropped frames and loss of audio sync when using Final Cut Pro, and explains how to fix them.

Many audio sync issues stem from dropped frames on capture or output. Nearly all dropped frames are due either to incorrectly configured hardware or incorrect preference settings. The leading causes of dropped frames are:

• There is not enough memory (RAM) allocated to Final Cut Pro. Final Cut Pro should ideally have 80 MB to 150 MB of RAM allocated to it. Refer to article 58630: " Final Cut Pro: Allocating Memory. "
• AppleTalk is turned on. It should be turned off.
• Virtual Memory is turned on. It should be turned off.
• Zooming in on the Canvas. You should not see scroll bars on the Canvas. Its size should be set to "Fit to Window" or smaller.
• The computer monitor is set to a low refresh rate. The resolution in the Monitors control panel should be set to 75 Hz or higher, see article 25117: " Final Cut Pro: 60 Hz Monitor Refresh Rate Interferes With Playback "
• The Canvas and Viewer windows are overlapping. They should not.
• There are too many Real Time audio tracks selected in the General Preferences.
• Incorrect version of the ATI Extensions are installed.
• The Canvas is set to a size other than 100 percent or 50 percent when used with a Targa board. The Targa plays back smoothly only at these sizes.
• On a PowerBook computer, processor cycling is on. Turn off processor cycling in the Advanced Settings pane of the Energy Saver control panel.
• Using unqualified hard drives. See below.
• The capture drive is fragmented. See below.
• Using the Mirror to Desktop option with a slow computer. See below.
• The Autosync Compensator is not turned on in the General Preferences. See below.
• There are too many sequences open at the same time. See below.
• Playing back sequences with numerous short edits. See below.
• You have switched your sequence settings on a Digital Voodoo D1 Desktop video card from 8-bit to 10-bit (or vice-versa) without quitting and reopening Final Cut Pro.
• You have TCP/IP set to DHCP when no DHCP server is available. Either set TCP/IP to Manual (with the appropriate IP address) or turn it off using the TCP/IP control panel.

The most common source of difficulties relating to audio sync is dropped frames during video capture.

If you try to capture video to an unqualified storage device (see article 58636: " Final Cut Pro: What Kind of Hard Drive Should I Buy? ") the resulting frames that are dropped interfere with audio sync. This loss of sync appears to increase over time (drift), and does not disappear when stopping and starting the affected video clip. In particular, this issue may happen if you attempt to capture M-JPEG video clips using the internal hard disk that came with your computer. The solution in this case is to recapture all affected video clips using a qualified storage device. This device should be selected in the scratch disks preferences tab prior to reinitiating video capture. Click Set, and select a storage volume to capture to.

Figure 1 Scratch disk preferences tab

To avoid this issue in the future, leave the Report or Abort On Dropped Frames option in the preferences General tab enabled so as to be alerted to potential issues as they occur.

Figure 2 Abort and report dropped frames option in the capture preferences tab

A less likely source of dropped frames on capture or playback may be overly fragmented hard disks. See article 17933: " Macintosh; How Often Should I Defragment My Hard Drive? " It is preferable to capture to storage volumes specifically reserved for video, and avoid filling them up with numerous files unrelated to the project at hand. Still, in the event of a long project where some clips are captured, others are deleted, then more are captured, and so on, even the cleanest storage volume may become overly fragmented. You may diagnose this situation with the use of a utility such as Norton Speed Disk or Alsoft DiskExpress Pro. Should it be seriously fragmented to the point of impeding performance, you have these options:

1. Quit Final Cut Pro, back up your project file, and delete all the clips from the affected volumes (delete only media that can be recaptured. Do not delete graphics, audio, or project files.) Upon reopening your Final Cut Pro project, you will find that all your video clips are now off-line. Simply recapture them, and your performance should be improved.

2. Copy all the files from the fragmented volume to a blank volume with enough space. The act of copying files defragments them on the volume to which they are copied. Afterwards, simply delete the files from the original, fragmented volume, and you are ready to capture more clips to it.

Note: if trying the second option you may avoid having to relink the clips by doing the following:

• Quit Final Cut Pro before you begin.
• Do not change the filenames.
• Keep the files in the same folder.
• Rename the new storage volume with the same name as the volume from which you copied the clips (renaming the prior volume first, of course). See page 214 of the Final Cut Pro 2 manual for more information on how to relink media should this be necessary.

3. A more time-intensive solution is to back up your project file, then use disk defragmenting software such as Norton Speed Disk or Alsoft DiskExpress Pro to defragment your volume.

If the individual clips all have good audio sync yet sync is still being lost, the issue is probably dropped frames on output. There are several preference settings inside of Final Cut Pro that could affect this.

Having too many Real-Time Audio Mixing tracks specified in the General Preferences panel can cause dropped frames if the computer speed is not fast enough to handle them. You may specify a smaller number of tracks to overcome this.

Figure 3 The Real-time Audio Mixing field

When using imported DV video clips, (usually long ones) the audio sync may drift over time if Sync Adjust Movies is not turned on. This is a feature that is designed to ensure sync in long, unbroken clips captured from certain cameras, specifically certain Canon cameras.

Note: Timecode breaks or dead video recorded in a clip while the Sync Adjust Movies is turned on results in the Sync Adjust Movies becoming disabled for that clip.

Figure 4 Sync Adjust Movies

With slower computers, disabling the Mirror to Desktop option in the External Video tab of the Audio/Vidoe Settings window may also solve the issue. Mirroring to the desktop is a processor-intensive task, and disabling this feature frees up more of the computer's resources to performing video output correctly.

Figure 5 The Mirror on Desktop options in the General Preferences Tab

Another potential cause of issues during output involves having too many sequences open simultaneously in the Timeline window. Especially in the case of complex edits, having more than one sequence open at the same time can affect playback performance. To eliminate this, close all sequences except the one you want to output to video.

If still faced with sync issues or dropped frames, a final solution could be to render out the entire video sequence to a single file, using the Export>Final Cut Pro Movie command, shown below.

Figure 6 Final Cut Pro Movie Menu

Projects with a large number of short edits can sometimes overwhelm a storage device's ability to jump from one clip to another, resulting in dropped frames. Writing out one single file eliminates this situation. When rendering out using the Final Cut Pro Movie command, disable the Recompress All Frames feature to save on unnecessary rendering time.

Figure 7 The export Final Cut Pro Movie dialog, with Recompress All Frames disabled

Another solution, particularly in the case of long sequences, would be to split up a single long sequence into multiple short sequences, outputting them to tape one at a time. See pages 399 and 1123 of the Final Cut Pro 2 manual for more information..

Lost Sync Despite No Dropped Frames

Occasionally, after going through all these possible solutions, there may be sync issues that do not result from dropped frames at all. Instead, such losses of sync manifest themselves as seemingly insoluble issues. In these cases, you are advised to quit Final Cut Pro, move the Final Cut Pro preferences files (in the Preferences Folder) into the Trash, and empty it. Refer to article 31197: " Final Cut Pro: How to Delete the Preferences File ". Upon opening Final Cut Pro, these issues should disappear, although you may have to recapture clips that were previously imported.

Note: This article provides information about non-Apple products. Apple Computer, Inc. is not responsible for its content and mention of this product should not be interpreted as a recommendation by Apple. Please contact the vendors for additional information.