User manual

651
Synchronization
Timecode (positional references)
Master and slave
Calling one device the “master” and another the “slave” can lead to a great deal of
confusion. The timecode relationship and the machine control relationship must be
differentiated in this regard.
In this document, the following terms are used:
- The “timecode master” is the device generating position information or timecode.
- The “timecode slave” is any device receiving the timecode and synchronizing or
“locking” to it.
- The “machine control master” is the device that issues transport commands to the
system.
- The “machine control slave” is the device receiving those commands and
responding to them.
For example, Cubase could be the machine control master, sending transport
commands to an external device which in turn sends timecode and audio clock
information back to Cubase. In that case, Cubase would also be the timecode slave at
the same time. So calling Cubase simply the master is misleading.
Ö In most scenarios, the machine control slave is also the timecode master. Once it
receives a play command, that device starts generating timecode for all the timecode
slaves to synchronize to.
Timecode (positional references)
The position of any device is most often described using timecode. Timecode
represents time using hours, minutes, seconds, and frames to provide a location for
each device. Each frame represents a visual film or video frame.
Timecode can be communicated in several ways:
- LTC (Longitudinal Timecode) is an analog signal that can be recorded on tape. It
should be used for positional information primarily. It can also be used for speed
and phase information as a last resort if no other clock source is available.
- VITC (Vertical Interval Timecode) is contained within a composite video signal. It is
recorded onto video tape and is physically tied to each video frame.
- MTC (MIDI Timecode) is identical to LTC except that it is a digital signal
transmitted via MIDI.
Timecode standards
Timecode has several standards. The subject of the various timecode formats can be
very confusing due to the use and misuse of the shorthand names for specific
timecode standards and frame rates. The reasons for this confusion are described in
detail below. The timecode format can be divided into two variables: frame count and
frame rate.
Frame count (frames per second)
The frame count of timecode defines the standard with which it is labeled. There are
four timecode standards:
• 24 fps Film (F)
This frame count is the traditional count for film. It is also used for HD video formats
and commonly referred to as “24
p”. However, with HD video, the actual frame rate
or speed of the video sync reference is slower, 23.976 frames per second, so
timecode does not reflect the actual realtime on the clock for 24p HD video.
• 25 fps PAL (P)
This is the broadcast video standard frame count for European (and other PAL
countries) television broadcast.