Editing MIDI timecode (section)

{{Short description|SMPTE timecode as MIDI messages}}
{{More citations needed|date=November 2024}}
{{Use British English|date=December 2024}}

'''MIDI time code''' ('''MTC''') embeds the same timing information as standard [[SMPTE timecode]] 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 [[:en:SysEx#System Exclusive messages|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. <ref>{{Cite web |title=SMPTE & MTC (MIDI Time Code) |url=https://www.soundonsound.com/techniques/smpte-mtc-midi-time-code |access-date=2024-11-29 |website=www.soundonsound.com}}</ref>

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 [[Frame rate|film work]]) 
* 25 frame/s (standard rate for [[PAL]] video)
* 29.97 frame/s (drop-frame timecode for [[NTSC]] video)
* 30 frame/s (non-drop timecode for NTSC video) <ref>{{Cite web |title=MIDI Time Code and MIDI Clock Explained |url=https://www.dummies.com/article/technology/software/music-recording-software/general-music-recording-software/midi-time-code-and-midi-clock-explained-179973/ |access-date=2024-11-29 |website=dummies |language=en}}</ref>

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. <ref>{{Cite web |last=Schütte |first=Benjamin |last2=Bachmann |first2=Cristina |title=Timecode Standards |url=https://archive.steinberg.help/nuendo/v10/en/cubase_nuendo/topics/synchronization/synchronization_timecode_standards_c.html |access-date=2024-11-29 |website=archive.steinberg.help |language=en-US}}</ref>

MTC allows the synchronisation of a [[MIDI sequencer|sequencer]] or [[Digital audio workstation|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. 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.