Specifications

Pro Tools Reference Guide 548
Final Audio Destination: Video
If you are working with video that was trans-
ferred from film, your audio source is at film
speed, and the final layback destination is NTSC
video (or television), and you would like to pro-
vide a digital transfer to your clients, you will
need to alter the above recipe slightly. Keep in
mind that when you are working in Pull Down
mode, your active sample rate is 44.056 kHz (if
the audio was recorded at 44.1 kHz) or
47.952 kHz (if the audio was recorded at
48 kHz).
Pull Down the Audio Source
Some professional DAT machines will let you
pull down the sample rate to 44.056 kHz (and
47.952 kHz). You can record this audio into
Pro Tools using a D-A-D (digital-to-analog-to-
digital) process, or Digidesign’s 192 I/O Sample
Rate Conversion option. 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 necessary.
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 window. Then select an Audio
Rate Pull Up option in the Session Setup win-
dow (and on your synchronizer if it isn’t a SYNC
I/O) before you record in the production audio.
In this case, while the production audio is run-
ning at 44.1 or 48 kHz, Pro Tools is running
(and recording) at a rate of 44.144 or 48.048
kHz. After all the production audio has been re-
corded into Pro Tools, reset the Audio Rate Pull
to none in the Session Setup window, and on
your hardware synchronizer if it is not a
SYNC I/O. After you deselect Pull Up, the re-
corded audio will play back 0.1% slower, syn-
chronized with the video, while achieving a true
playback sample rate of 44.1 or 48 kHz. Note
that this process is designed for a final destina-
tion 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 sample
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 au-
dio back to film speed.
On the 192 I/O and 192 Digital I/O, the inputs
on the Digital I/O card feature real-time sample
rate conversion.
Using Digital Input
If you are working with Pull Up or Pull Down,
do not “resolve” to any digital inputs that are
used as audio sources in Pro Tools. This would
override the use of the SYNC I/O as the clock ref-
erence. Any equipment providing digital audio
sources to Pro Tools should be synchronized ex-
ternally.
You will also need to select the Audio Rate
Pull Up/Down option in the Session Setup
window.