Frank Kurth's Matlab-MIDI Tools
On this page our group provides - free of charge and free of warranty - for use of the research community, a small toolbox of utilities for handling standard MIDI files (SMFs) under Matlab. The toolbox requires Matlab version 5 or higher (tested on Matlab 5, Matlab 6 (Rev. 13)).
Our motivation for importing MIDI files into the Matlab environment was primarily to access the MIDI notes. Hence, the primary data structure (midi) only containes the note events. Additional information such as system exclusive messages are also read from the MIDI files, but only stored in a special structure (ext) as a binary string and not processed further.
The following files are contained in the toolbox:
- midird3.m takes two arguments, the first being the name of the MIDI file. If the second, optional, parameter is given, which is as well expected to be a string, an additional text file is output containing a textual representation of the MIDI file. (E.g., [midi,info,ext,ms_per_quarter,ms_per_tick] = midird3('demo.mid','demo.txt'); produces, for the input MIDI file demo.mid, an output text file called demo.txt, as well as the matlab structures midi, info and ext which contain the midi data extracted from demo.mid.) The numbers ms_per_quarter and ms_per_tick return the time in milliseconds per quarter note and per MIDI tick, respectively (if this information is contained in the MIDI-file - otherwise, both nombers are set to zero).
- midiwr.m takes four parameters, a file name for the destination MIDI file and the structures midi, info and ext (see above). E.g., midiwr('demo2.mid',midi2,info2,ext2); creates, for the input structures midi2,info2,ext2, a standard MIDI file called demo2.mid corresponding to the input structures. In particular, [midi,info,ext] = midird3('demo.mid'); midiwr('demo.mid',midi,info,ext); should reproduce the original MIDI file demo.mid.
- midiTimeCurve.m is a modification of midiwr.m, with syntax
newtime=midiTimeCurve(fname,midi,info,ext,timecrv);
An output MIDI file fname is created from the midi structures midi, info, and ext, where the time axis i s modified according to the vector timecrv. As an example, timecrv=[1 2] creates a new MIDI file starting at the same tempo as specified in the midi structures and ending with 2x the tempo. In another example, using timecrv=[1 2 1 0.5 1], the time-line contained in the midi structures is plit into four parts of equal length: during the first part the tempo decreases from 1x to 2x the original speed, in the second part it increases back to 1x speed, then down to 0.5x speed, and finally back to 1x speed. The value newtime returns the new time curve (may be used for visualization purposes, e.g., using plot(newtime)).
Example: The file BM01A-ModifiedTimeCurve.mid has been generated from the file BM01A.mid using the commands
[midi,info,ext] = midird3('BM01A.mid');
newtime=midiTimeCurve('BM01A-ModifiedTimeCurve.mid',midi,info,ext,[1 2 1 0.5 1]);
- pianoroll.m creates a (very simple!) piano roll plot of the input data (typically given as the midi data structure obtained from midird3, see above).
- MergeTracks.m merges multiple tracks contained in the struct array midi into one single track while preserving time consistency (mind that MIDI events are time-stamped using delta ticks, i.e., a relative time representation.
- midi2note.m is an auxiliary function required by pianoroll.m
- demo.mid and demo.txt are simple demo files - the command [midi,info,ext] = midird3('demo.mid','demo.txt'); should reproduce the file demo.txt when applied (to the simple MIDI file demo.mid).
Download toolbox as ZIP archive. (New version: May, 11th 2004)
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