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96 lines
2.2 KiB
Ruby
Executable file
96 lines
2.2 KiB
Ruby
Executable file
#!/usr/bin/env ruby
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#
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# Script to investigate priorities of different MIDI instruments,
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# so that the factor used to determine priority can be identified.
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#
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# We go through each pair of MIDI instruments, ie. (0, 1), (1, 2), ...
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# etc. We then set channel 1 and 2 to use each of the instruments.
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# Then we play enough notes (9) to fill every OPL voice, so that the
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# allocated voices linked list looks like this:
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#
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# (start)-> 1-2-1-1-1-1-1-1-1
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#
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# Once all voices are filled, try to play a note on channel 2. If
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# channel 2 is a higher priority than channel 1, the first voice
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# in the list (using channel 1) will be discarded for the new voice,
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# but if channel 1 is a higher priority, the existing channel 2
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# voice will be discarded to keep the channel 1 voice.
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#
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# From this we can work out how the priority of different instruments
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# compares, and compare this to the instrument data to see if something
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# fits.
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def note_on(delay, channel, note, volume)
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# note on
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putc delay
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putc 0x90 + channel
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putc note
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putc volume
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end
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def note_off(delay, channel, note)
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# note on
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putc delay
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putc 0x80 + channel
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putc note
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putc 0x00
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end
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def program_change(delay, channel, instrument)
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putc delay
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putc 0xc0 + channel
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putc instrument
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end
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def end_of_track
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putc 0x00
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putc 0xff
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putc 0x2f
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putc 0x00
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end
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# Turn off the note in e1m1-cropped.mid
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note_off(0, 2, 40)
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# Go through each pair in turn.
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for i in 0..32
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# Set the instruments for the two channels.
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program_change(0x1, 1, i)
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program_change(0x1, 2, i + 1)
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# Play some notes.
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note_on(0xf, 1, 0x40, 0x40)
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note_on(0xf, 1, 0x41, 0x40)
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note_on(0xf, 1, 0x42, 0x40)
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note_on(0xf, 1, 0x43, 0x40)
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note_on(0xf, 1, 0x44, 0x40)
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note_on(0xf, 1, 0x45, 0x40)
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note_on(0xf, 1, 0x46, 0x40)
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note_on(0xf, 2, 0x47, 0x40)
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note_on(0xf, 1, 0x48, 0x40)
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# The overflow note:
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note_on(0xf, 2, 0x49, 0x40)
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# Turn off all the notes:
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note_off(0xf, 1, 0x40)
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note_off(0xf, 1, 0x41)
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note_off(0xf, 1, 0x42)
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note_off(0xf, 1, 0x43)
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note_off(0xf, 1, 0x44)
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note_off(0xf, 1, 0x45)
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note_off(0xf, 1, 0x46)
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note_off(0xf, 2, 0x47)
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note_off(0xf, 1, 0x48)
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note_off(0xf, 2, 0x49)
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end
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end_of_track
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