Note_Off is displayed as Note_On

[sharmilamani]

Hi,
How to identify the start time and duration of note played from mid file ?
as i went through the mido read me time in message refers to wait time from previous event. is this the start time of the note ? also i don't see a "note_off message".

Below is a midi file printed using mido. In this file, the key c4 is pressed and released 10 times.
Kindly help in understanding

1. start of each key press in seconds ?
2. time duration / end of each key press ?
3. time gap between two key press ( start of second key - end of first key)

MidiFile(type=1, ticks_per_beat=24, tracks=[
MidiTrack([
MetaMessage('set_tempo', tempo=500000, time=0),
MetaMessage('time_signature', numerator=4, denominator=4, clocks_per_click=24, notated_32nd_notes_per_beat=8, time=0),
MetaMessage('key_signature', key='C', time=0),
MetaMessage('end_of_track', time=0)]),
MidiTrack([
Message('program_change', channel=0, program=4, time=0),
Message('note_on', channel=0, note=60, velocity=46, time=54),
Message('note_on', channel=0, note=60, velocity=0, time=30),
Message('note_on', channel=0, note=60, velocity=40, time=30),
Message('note_on', channel=0, note=60, velocity=0, time=36),
Message('note_on', channel=0, note=60, velocity=33, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=36),
Message('note_on', channel=0, note=60, velocity=38, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=36),
Message('note_on', channel=0, note=60, velocity=34, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=42),
Message('note_on', channel=0, note=60, velocity=40, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=36),
Message('note_on', channel=0, note=60, velocity=45, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=42),
Message('note_on', channel=0, note=60, velocity=48, time=48),
Message('note_on', channel=0, note=60, velocity=0, time=42),
Message('note_on', channel=0, note=60, velocity=51, time=36),
Message('note_on', channel=0, note=60, velocity=0, time=42),
Message('note_on', channel=0, note=60, velocity=28, time=24),
Message('note_on', channel=0, note=60, velocity=0, time=42),
MetaMessage('end_of_track', time=0)])

[jnguyen1098]

According to the MIDI 1.0 specification, page 73, a MIDI note-on event (9n) with a velocity of 0 is considered a note-off. In your example, every note_on event is immediately followed with another note_on but with a velocity=0, thereby functioning as the note_off(s) you look for.

The advantage of this is that, assuming an uninterrupted stream of note-on and note-off events, a space-conscious implementation may take advantage of the running status. Your file likely employed such encoding methods.

I haven't looked at the mido codebase, so my answer is mostly related to MIDI as a whole, not this project in particular, which appears to be completely in-spec.

Edit: related discussions:

• note_on and note_off both parsed as note_on #130
• Note_off registering as note_on #158
• https://www.kvraudio.com/forum/viewtopic.php?t=291892

[rdoursenaud]

@jnguyen1098 perfectly explained the reason. It is not a bug but an intrinsic design of the MIDI protocol.