Lip-sync (video/audio synchronization) can be a problem when burning-in MOV and MP4 input files that were shot by smart phones and similar devices.
In most cases you should find that the burnt-in output files should play back OK on your computer, but if you need to import them into video editing or processing software that is configured to use a fixed frame rate (e.g. DVD authoring software), you may find that the audio slowly slips out of sync with the video.
Why does this happen?
Well, some smart phones tend to shoot at frame-rates that do not exactly match the standard PAL and NTSC frame rates. Sometimes the frame rate may be fairly close to the standard rates, but even a small mismatch may cause problems in some third-party software. Also, the frame rate of some devices may even vary to a greater or lesser degree while it is recording, so the file has no fixed frame rate! These issues can cause problems when importing them into software that needs to export its final video files in one of the standard frame rates - for example DVD Authoring software where the official DVD standards require strictly fixed frame rates of 25 or 29.97 frames per second.
In such cases the third-party software will have to do some sort of frame rate conversion, and some software products will do this more successfully than others. For example, the software could omit frames if the fixed frame rate video stream was getting too far behind the audio stream, or duplicate an occasional frame if the video was getting too far ahead of the audio - in either case this would be visible as a very slight jerk in the video but at least both streams should stay in sync. Those software products that don't quite manage to do the frame rate conversion well enough will typically produce video where the audio slowly drifts out of sync with the video. This can be very frustrating and as each software product behaves differently there is no single solution to this - and unfortunately some software may simply be unable to produce correctly sync'ed video at all.
If you are experiencing sync problems with files produced by other software, first check whether the files produced by DVMP Pro are OK by playing them in Windows Media Player or VLC. If they are not in sync then try again with another software player (for example if Windows Media Player plays them out of sync then try playing the file in VLC). If at least one software player can play the file in-sync, then you can be sure that the file itself is OK and the problem lies with the software that you are importing it into.
Assuming the problem lies with the other software, try using different output file types in DVMP Pro. Using the AVI output type (with say the Lagarith AVI Video Compressor) can sometimes be successful. It depends entirely on how the other software transcodes and remultiplexes the file type to its final output video file.
Also, be aware that some software has difficulty importing or playing AVI files that contain audio in AC-3 format, so if your camcorder records its audio in AC-3 format then try ticking the Convert audio to PCM in output AVI file option in Tools > Burn-in > Output before you do a burn-in. You can find out more about this issue in the AVI Output Type section of the Options - Burn-in Output topic.
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