User`s guide

Chapter 23: Synchronization Concepts 337
Pull Down the Audio Source
Some professional DAT machines will let
you Pull Down the sample rate to 44.056
kHz, then you can record this audio into
Pro Tools using a D-A-D (digital-to-analog-
to-digital) process. Then your audio will be
at the correct speed for the remainder of
the project, since the final destination is
video, and no Pull Down or Pull Up is nec-
essary.
Pull Up Pro Tools While Recording
If you cannot Pull Down your source, you
can accomplish the same thing by Pulling
Up Pro Tools, and setting your SMPTE
frame format to 30 FPS, before recording in
the production sound. First select 30 FPS as
the frame format in the Session Setup Win-
dow. Then select Pull Up in the Session
Setup window (and on your synchronizer if
it isn’t a USD or SSD) before you record in
the production audio. In this case, while
the production audio is running at 44.1 or
48 kHz, Pro Tools is running (and record-
ing) at a rate of 44.144 or 48.048 kHz. After
all the production audio has been recorded
into Pro Tools, deselect Pull Up in the Ses-
sion Setup window and on your hardware
synchronizer if it is not a USD or SSD. After
you deselect Pull Up, the recorded audio
will play back 0.1% slower, synchronized
with the video, while achieving a true play-
back sample rate of 44.1 or 48 kHz. Note
that this process is designed for a final des-
tination of video; to bring this audio back
up to film speed you would have to Pull Up
Pro Tools and record to a destination that
is not Pulled Up.
Note on Sample Rate Conversion
In many cases, you have to perform a sam-
ple rate conversion at some point, either
digitally, or by recording in audio using an
analog stage (D-A-D). The only situation
where sample rate conversion never has to
be performed is when you are working with
film speed audio and your final destination
format is film. Then you can simply Pull
Down Pro Tools while you work with the
video, then deselect Pull Down to set the
audio back to film speed.
Using Digital Input
Do not set Pro Tools channels 1 and 2 to
Digital Input format while working with
Pull Up or Pull Down. This will override
any clock reference information, such as
the Reference Video information from a
USD.