MIDI file parsing homework

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Revision as of 04:36, 21 January 2016 by Craig (Talk | contribs) (Assignment)

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1 Assignment

  1. Find a MIDI file on the web. Tip: include filetype:midi when searching for MIDI files in Google searches.
  2. Save the MIDI file to your desktop and open it (usually double-clicking to open with the default MIDI playing program on your computer).
  3. If it plays correctly, drag and drop the MIDI file from your desktop onto the binasc online webpage.
  4. Parse the resulting display of the MIDI file's hexadecimal bytes by hand. Make note of the number of tracks in the file; whether it is type-0 or type-1 (or type-2), and how many ticks per quarter note (or SMPTE frames/subframes) are used for basic timing in the file.
  5. Parse at least 25 time/message pairs in one of the tracks of the MIDI File. Note that type-1 files only stores meta messages such as tempo changes in the first track. If your file is a type-1 file, try parsing a few of these meta messages, and then switch to another track with notes.
  6. Give the basic meaning of MIDI messages (such as this is a note-on messages for pitch A4, or this is a tempo meta message).
  7. Decoding VLVs for delta timings is optional.
  8. Extra Credit: Write your own Standard MIDI File parser which will do this homework for you.
  9. Email MIDI file and your parsing to you know whos.

2 Example

Here is the simple example done in class using File:Twinkle.mid. Converting bytes into a list of hexadecimal numbers with binasc online:

4d 54 68 64 00 00 00 06 00 00 00 01 00 80 4d 54 72 6b 00 00 00 8c 00 ff 58  
04 04 02 30 08 00 ff 59 02 00 00 00 90 3c 28 81 00 90 3c 00 00 90 3c 1e 81 
00 90 3c 00 00 90 43 2d 81 00 90 43 00 00 90 43 32 81 00 90 43 00 00 90 45 
2d 81 00 90 45 00 00 90 45 32 81 00 90 45 00 00 90 43 23 82 00 90 43 00 00 
90 41 32 81 00 90 41 00 00 90 41 2d 81 00 90 41 00 00 90 40 32 40 90 40 00 
40 90 40 28 40 90 40 00 40 90 3e 2d 40 90 3e 00 40 90 3e 32 40 90 3e 00 40 
90 3c 1e 82 00 90 3c 00 00 ff 2f 00

Example parsing to be done by hand (don't worry about unpacking VLV timestamps), or write your own extra-credit MIDI file parser:

4d 54 68 64 MIDI header chunk marker ("MThd")

00 00 00 06      Bytes to follow in header chunk (6)
00 00            file format: Type-0 (0 == single track format)
00 01            number of tracks (1)
00 80            ticks per quarter note (128)

First (and only track):

4d 54 72 6b       MIDI track chunk marker ("MTrk")
00 00 00 8c       Bytes to follow in track chunk (140 bytes)


VLV     MIDI message
============================================
0       ff 58 '4 4 2 30 8       Meta-message for tempo
0       ff 59 '2 0 0            Meta-message for time signature
0       90 '60 '40              Note on, C4
128     90 '60   0               Note off, C4
0       90 '60 '30              etc.
128     90 '60   0
0       90 '67 '45
128     90 '67   0
0       90 '67 '50
128     90 '67   0 
0       90 '69 '45
128     90 '69   0
0       90 '69 '50
128     90 '69   0
0       90 '67 '35
256     90 '67   0
0       90 '65 '50
128     90 '65   0
0       90 '65 '45
128     90 '65   0
0       90 '64 '50
64      90 '64   0
64      90 '64 '40
64      90 '64   0
64      90 '62 '45
64      90 '62   0
64      90 '62 '50
64      90 '62   0
64      90 '60 '30
256     90 '60   0
0       ff 2f 0                Meta-message for end-of-track