MIDI timecode

MIDI time code (MTC) 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.

Unlike standard SMPTE timecode, the eight-message MIDI timecode sequence carries a two-bit flag value that identifies the rate of the timecode, specifiying it as either:

• 24 frame/s (standard rate for film work)
• 25 frame/s (standard rate for PAL video)
• 30/1.001 frame/s (Drop-Frame timecode for color NTSC video)
• 30 frame/s (monochrome NTSC video)

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

• Linear timecode
• Vertical interval timecode
• Burnt-in timecode
• CTL timecode
• AES-EBU embedded timecode
• Rewritable consumer timecode

External links

• MIDI Time Code information