Why allow lip synch?

[oldsalt]

All over the forum I've seen references to the DVD problem of "lip synch".
I'm having quite a problem with it myself. What I can't understand is why the problem continues to exist. Many years ago I coded constantly (albeit in languages no longer in use) and it is my very strong intuitive feelings that the problem of lip synch should be vunerable on at least a couple of fronts. I'm suprised that both the video and audio portions of the code on the disk or in the mpg file don't have "synch bytes" that would be measured and compared in real time and a correction factor applied to the presentation of data on screen and speaker.
Failing that, a user-controlled utility could be of use without changes to file standards. Tapped intervels clicked on the mouse or on a specified key could represent the error interval (one click when you hear the "O" and the other when you see the "O") This may have to be repeated near the end of the file as synch problems seem to be progressive. Please shoot me down. The flames will insue as a great learning experience.

[ImaWeTodd]

Ya know, I've never seen a commercial DVD with lip sync problems. Maybe the commercial guys have such a program/standard, and it's us 'hobbyists' who are in the dark.

On another note, I'm having a terrible time fixing lip sync on an old Kung Fu movie I captured off a local channel last Sunday afternoon. None of the guides seem to help. Any suggestions would be appreciated.

[oldsalt]

I agree. My point is that is should be easy software to write. Even if MPEG standards are controlled by the power brokers so that the relatively simple concept of internal synch bytes are purposely suppressed, the second concept of a user fixit utility that would do the correction and then re-write a corrected high quality MPEG should a pretty straight forward job for many of the basement programmers out there.

[ktnwin]

I can share a few things about lip sync issue:
1) first video and audio are encoded separately (maybe with different softwares), depending on the encoding software, the two compressed streams (video and audio) could be in sync or not in sync
2) the original audio could be sampled at one frequency and converted to a different sampling frequency before compression, another source of sync. problem
3) I have seen some DVD, VCD playing fine on one player but have lip sync problem on another (trouble to read media ???)
4) capturing analog video lends itself to lip sync problem (due to software issue).
My four cents.