MIDI timecode

related topics
{system, computer, user}
{film, series, show}
{black, white, people}

MIDI time code (MTC), or MIDI time division, embeds the same timing information as standard SMPTE time code as a series of small 'quarter-frame' MIDI messages. There is no provision for the user bits in the standard MIDI time code messages, and SysEx messages are used to carry this information instead. The quarter-frame messages are transmitted in a sequence of eight messages, thus a complete timecode value is specified every two frames. If the MIDI data stream is running close to capacity, the MTC data may arrive a little behind schedule which has the effect of introducing a small amount of jitter. In order to avoid this it is ideal to use a completely separate MIDI port for MTC data. Larger full-frame messages, which encapsulate a frame worth of timecode in a single message, are used to locate to a time while timecode is not running.

Unlike standard SMPTE timecode, MIDI timecode's quarter-frame and full-frame messages carry a two-bit flag value that identifies the rate of the timecode, specifying it as either:

  • 24 frame/s (standard rate for film work)
  • 25 frame/s (standard rate for PAL video)
  • 30 frame/s (drop-frame timecode for NTSC video)
  • 30 frame/s (non-drop timecode for NTSC video)

MTC distinguishes between film speed and video speed only by the rate at which timecode advances, not by the information contained in the timecode messages; thus, 29.97 frame/s dropframe is represented as 30 frame/s dropframe at 0.1% pulldown.

MTC allows the synchronisation of a sequencer or DAW with other devices that can synchronise to MTC or for these devices to 'slave' to a tape machine that is striped with SMPTE. For this to happen a SMPTE to MTC converter needs to be employed. Please note that it is possible for a tape machine to synchronise to an MTC signal (if converted to SMPTE), if the tape machine is able to 'slave' to incoming timecode via motor control, which is a rare feature.

See also

External links

Full article ▸

related documents
Motorola 68010
Connectionless mode transmission
File archiver
JPEG Network Graphics
Carrier sense multiple access with collision avoidance
Render farm
Single-frequency signaling
Killer poke
EPOC (computing)
Tru64 UNIX
Intel 8088
Microsoft PowerPoint
Intel 8048
Carrier system
Modified AMI code
Mesa (programming language)
Sorcerer (operating system)
Signal processing
Cell relay
Helix (project)
Yet another Setup Tool
Au file format