>I've decided that I need a (relatively)
>inexpensive, compact, high-quality sound recorder for audio for my short
>films.
This reply is somewhat technical, but synchronized audio-for-video using separate
recorders does not "just happen"; some
basic principles (not always clearly understood) that have evolved from the early days
of sound movies are involved. I have
not tried to synchonize audio-for-video with MD, but I do have experience with ADAT
(Alesis digital multitrack). There are 2
problems to be solved when recording synchronized audio:
1) Getting the audio and video to play back at with the same speed relationship that
was present during recording
(maintaining synchronization). This problem sounds trivial, but its really not
simple. The separate crystals in the audio and
video recorders *will* cause the audio and video to drift apart much quicker than one
would think. Alesis solves this
problem by using the video signal as a timebase instead of the ADAT's crystal. Thus
the ADAT's record and playback
speed is locked to the video record/playback speed. This feature is not available in
any consumer MD units, but may be
available in "pro" MD units. (For sound movies, they solved this problem by running
the synchronous motors in the camera
and sound recorder from the same power source, and by using spocketted film and
sprocketted sound tape to ensure that
no "slip" occured.)
2) Getting the audio and video started at the same time (initial synchronization).
The ADAT solves this problem by
"chasing" SMPTE time code that was recorded on the video tape. Again, consumer MD
has no provision for "chasing". (In
movies, they used a "clapboard" to mark each take; the "clap" could be heard in the
sound, marking the precise spot and the
clapboards arms would touch at the precise frame of the picture.)
A while back we had the audio-for-video discussion and it was suggested that SMPTE
time code from the camera could be
recorded on the right track of the MD. The playback video deck would then
continuously "chase" the time code recovered
from the MD during playback. Realize that "chasing" is intended only to achieve
initial synchronization and should not be
relied upon to mantain sync. Since "chasing" by definition causes the audio and video
to "slip" until sync is achieved, it may
cause an occasional "burp" to regain sync if the audio and video sync is not locked
once initial sync has been achieved.
Another point that may cause problems is if MD audio is copied using a consumer
recorder. The sample-rate-converter in
the recorder is non-defeatable. That is, the copy, rather than being
sample-for-sample will be resampled since the play
deck and the record deck crystals *will* drift apart. If this happened, the copy
would no long be "locked" to the original
video, even if the original audio was. Again, pro MD may have a way of switching off
the sample-rate-converter so the
recording deck uses the recovered clock from the S/PDIF instead of it's own crystal.
Just some points to be aware of when cosindering audio-for-video...
-----------------------------------------------------------------
To stop getting this list send a message containing just the word
"unsubscribe" to [EMAIL PROTECTED]
