Audio-video lip sync issues? What causes them?

[morkys]

When watching a dvd and slowly the audio and video go out of sync, and your guest asks why the movie is starting to look like a bad kung fu edit, what is going on?

Is it at all possible that a scratched dvd can cause this to happen? I sometimes see this happening when I pause or go back and forth improperly, but tonight it happened twice, and each time I had to go back a scene << in order to re-sync the audio and video. I was watching a dvd for the first time on a "new to me" used Yamaha C750.

As mentioned above, I rarely ever saw it using my trusty old Panasonic CV51 dvd player. I swear I should look for another as a backup..

thanx in advance for any feedback,

[redwudz]

Two simple causes of sync error. The audio beginning is offset from the video start. This would cause the sync error to be the same throughout the video. Or the audio and video length are different. This would cause the sync error to gradually get worse during the video.

These can both be caused by errors or missing video or audio. To make it more complicated, you can have a combination of all of these.

Sync errors during playback can be caused by problems with the disc or problems with the player. I suspect the player has a que and tries to fill in missing data. Standalone players are good at this and can skip over a messed up area of a disc and still keep going. But if you FF or RW, the que can lose too much data. It should pick up and resync in a few seconds of regular play. ( This last is just my guess from what I've seen. Don't quote me on it. )

[morkys]

Thanx. Not sure what is happening. I played a DTS disc and the audio seemed fine. Now I am playing a disc using the dolby surround soundtrack, the same as what the dvd "the Client" had, and I suspect may be slowly going out of sync until the next chapter. At the start of a new chapter, it may be re-syncing, so-to-speak.

[morkys]

Played another disc yesterday and no problems. I guess I'll just see how it goes.