User`s guide

Pro Tools Reference Guide364
Stripe SMPTE Before You Record
All tapes in your setup (both audio and
video) must be striped with SMPTE Time
Code before any audio is recorded onto
them or to Pro Tools. If tapes aren’t striped,
your system may seem to work, but syn-
chronization will never properly occur. The
machines and Pro Tools will drift farther
and farther apart the longer they run.
The same problem occurs when audio is re-
corded into Pro Tools without a resolved
SMPTE source (if it was recorded before the
current session, for example.) The audio
cannot be accurately synchronized with an
analog tape recorder or video tape deck,
since the Pro Tools audio was not recorded
referenced to the SMPTE Time Code from
the analog tape deck or video tape deck.
Resolve All Components of Your
System
When striping time code, make sure that
the time code generator and the video
record deck are resolved to the same crystal
reference. For example, when striping
29.97 Drop Frame time code onto a VTR,
both the SMPTE generator and the VTR
should be resolved to the same “black
burst” or house sync generator. During
playback, the master deck should be re-
solved to “black burst” or house sync.
This convention provides compatibility for
your tape between the record and playback
passes, and when it’s played back in other
facilities on different equipment. This also
means that when playing back a tape
striped with time code, the playback deck
should be resolved to the same sync rate as
the record deck was resolved to at the time
of the striping. When you stripe an audio
transport with time code, it should be
“free-running” and unresolved, but should
be resolved with a house sync-referenced
synchronizer during playback.
Know the True Frame Rate on Your
Work Tape
If you get your video tapes from a produc-
tion company instead of recording them
yourself, be absolutely sure that they indi-
cate the SMPTE frame rate used on the tape
correctly.
The Digidesign SSD and USD (and some
third-party products) can be used to deter-
mine frame rate. See “Determining SMPTE
Frame Rate” on page 343.
29.97 FPS Non-Drop Rate Can Pose
Problems
29.97 FPS Non-Drop is a slightly slower
version of 30 FPS Non-Drop time code.
When used with color video, each video
frame now matches up with each SMPTE
frame without having to use a drop-frame
coding. This makes any frame number
mathematics much simpler, since no frame
numbers are dropped.
Unfortunately, some hardware and soft-
ware devices do not recognize 29.97 Non-
Drop as a separate frame rate. For example,
any standard SMPTE-to MTC-converter
does not explicitly recognize it. The user
must tell the convertor to expect 30 FPS
Non-Drop instead. In fact, many devices
that read SMPTE work acceptably by read-
ing 29.97 Non-Drop if they are set to ex-
pect 30 FPS Non-Drop.