User manual

653
Synchronization
Clock sources (speed references)
Clock sources (speed references)
Once the position is established, the next essential factor for synchronization is the
playback speed. Once two devices start playing from the same position, they must run
at exactly the same speed in order to remain in sync. Therefore, a single speed
reference must be used and all devices in the system must follow that reference. With
digital audio, the speed is determined by the audio clock rate. With video, the speed
is determined by the video sync signal.
Audio clock
Audio clock signals run at the speed of the sample rate used by a digital audio device
and are transmitted in several ways:
Word clock
Word clock is a dedicated signal running at the current sample rate that is fed over
BNC coaxial cables between devices. It is the most reliable form of audio clock and is
relatively easy to connect and use.
AES/SPDIF Digital Audio
An audio clock source is embedded within AES and SPDIF digital audio signals. This
clock source can be used as a speed reference. Preferably, the signal itself does not
contain any actual audio (digital black), but any digital audio source can be used if
necessary.
ADAT Lightpipe
ADAT Lightpipe, the 8-channel digital audio protocol developed by Alesis, also
contains audio clock and can be used as a speed reference. It is transmitted via
optical cables between devices.
Ö Do not confuse the audio clock embedded in the Lightpipe protocol with ADAT Sync,
which has timecode and machine control running over a proprietary DIN plug
connection.
MIDI clock
MIDI clock is a signal that uses position and timing data based on musical bars and
beats to determine location and speed (tempo). It can perform the same function as a
positional reference and a speed reference for other MIDI devices. Cubase supports
sending MIDI clock to external devices but cannot slave to incoming MIDI clock.
The Project Synchronization Setup dialog
Cubase’s Project Synchronization Setup dialog provides a central place to configure
a complex synchronized system. In addition to settings for timecode sources and
machine control settings, project setup parameters are available along with basic
transport controls for testing the system.
To open the Project Synchronization Setup dialog, proceed as follows:
• On the Transport menu, select the “Project Synchronization Setup…” option.
• On the Transport panel, [Ctrl]/[Command]-click the Sync button.
!
MIDI clock cannot be used to synchronize digital audio. It is only used for MIDI
devices to play in musical sync with one another. Cubase does not support being a
MIDI clock slave.