Roland VS-2000 Owner's Manual page 292

23—MIDI and Synchronization
What Do We Mean By "Timing Reference?"
A timing reference is a kind of message continuously transmitted from master to slave
to keep the devices synchronized. The VS-2000 works with two types of timing
references when synchronizing its hard disk recorder with another device.
SMPTE/MTC
The film and video industries use a steady stream of timing data called "SMPTE time
code" to keep devices tightly synchronized with each other as they play. A form of
SMPTE called "MIDI Time Code," or "MTC" can be transmitted and received through
MIDI cables along with other MIDI data. Both SMPTE and MTC provide very accurate
synchronization. The time code area of the VS-2000's current time location display
(Page 130) shows MTC/SMPTE hours, minutes, seconds frames and subframes.
The VS-2000 can be synchronized to any device that generates MTC. Most sequencers
support MTC, for example—not as many support SMPTE. The VS-2000 itself generates
MTC.
MIDI Beat Clock
MIDI beat clock—or "MIDI Clock" for short—is a pulse embedded in a stream of MIDI
data that can be used for synchronizing MIDI devices. MIDI clock synchronization isn't
as accurate as MTC-based synchronization. It does have one important use, however.
MIDI clock, along with MIDI Song Position Pointer ("SPP") messages, passes along
tempo and time signature information that can be used by the VS-2000 in the creation
of sync tracks and tempo maps, which we'll discuss in a moment.
The VS-2000 can record received MIDI clock information as a sync track that lets it act
as a master to slave devices that understand MIDI clocks and Song Position Pointer.
While the VS-2000 can generate MIDI clocks to slave devices that use this form of sync,
the VS-2000 itself can't be synchronized to MIDI clocks, since it's not an accurate
enough form of synchronization for the VS-2000's precise operations.
Song Position Pointer
About MTC Frame Rates
When you use MTC for synchronizing the VS-2000 with an external device, make sure
that the two devices are set to operate at the same MTC/SMTPE speed, or "frame rate."
The "frame" refers to how many frames of film or video occur in each second.
MTC/SMPTE can run at a few different frame rates, depending on the devices being
synchronized and the materials they're producing. It can run at:
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30 fps ('frames per second")—This speed is used by most MIDI sequencers and audio
devices. Black and white video also runs at this speed.
29.97N ("non-drop") fps—This is the speed at which United States' NTSC format
color video runs in non-time-critical situations, such as offline production work.
29.97D ("drop") fps—This is the speed at which United States' NTSC format live
color video runs during broadcasts and other time-critical situations.
25 fps—This is the speed at which European SECAM or PAL film, video and audio
equipment operates.
24 fps—Film, cell animation and certain audio devices run at this speed.
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