When synch'ing sound and picture, there are two things that must be
considered:
1) The sound recorder and the picture must run "at the same speed" to
maintain synch. This, the most basic requirement, was often handled in
movies by recording sound on sprocketted magnetic film using a synchronous
AC motor in the drive system that was excited from the same source as the
camera's drive motor. Now servo controlled drive systems are used in the
recorders, and they are syncronized to a master timing source.
2) The sound and picture must not be "offset" from each other. This was
originally accomplised by the clapboard, which placed a precise marker on
both the picture (when the two parts made contact) and the sound (when the
"clap" was heard) allowing the sound and picture to be started
simultaneously at a common event on the separate mediums. Now timecode is
used, and the "slave" machines chase the master to acquire lock.
Consumer MD recorders have no provision for locking the record or play
sample rate to an external source (video or film). So they only way things
can work is to record timecode on one track of the MD from a timing source
to which the camera is locked. The on playback, the MD would have to be
the timing master, with the picture playback locked to the time code
recovered from the MD.
This is not really a good solution, that is, having the MD be the timecode
master during playback. It would work in a pinch, but it would be much
better if the video frame rate of the camera and the sample rate of the
sound recorder had been locked in the first place.
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