MIDI-Perl-0.8/MIDI/Score.pod

=head1 NAME

MIDI::Score - MIDI scores

=head1 SYNOPSIS

  # it's a long story; see below

=head1 DESCRIPTION

This module provides functions to do with with MIDI scores.
It is used as the basis for all the functions in MIDI::Simple.
(Incidentally, MIDI::Opus's draw() method also uses some of the
functions in here.)

Whereas the events in a MIDI event structure are items whose timing
is expressed in delta-times, the timing of items in a score is
expressed as an absolute number of ticks from the track's start time.
Moreover, pairs of 'note_on' and 'note_off' events in an event structure
are abstracted into a single 'note' item in a score structure.

'note' takes the following form:

 ('note_on', I<start_time>, I<duration>, I<channel>, I<note>, I<velocity>)

The problem that score structures are meant to solve is that 1)
people definitely don't think in delta-times -- they think in absolute
times or in structures based on that (like 'time from start of measure');
2) people think in notes, not note_on and note_off events.

So, given this event structure:

 ['text_event', 0, 'www.ely.anglican.org/parishes/camgsm/chimes.html'],
 ['text_event', 0, 'Lord through this hour/ be Thou our guide'],
 ['text_event', 0, 'so, by Thy power/ no foot shall slide'],
 ['patch_change', 0, 1, 8],
 ['note_on', 0, 1, 25, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 29, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 27, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 20, 96],
 ['note_off', 192, 0, 1, 0],
 ['note_on', 0, 1, 25, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 27, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 29, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 25, 96],
 ['note_off', 192, 0, 1, 0],
 ['note_on', 0, 1, 29, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 25, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 27, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 20, 96],
 ['note_off', 192, 0, 1, 0],
 ['note_on', 0, 1, 20, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 27, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 29, 96],
 ['note_off', 96, 0, 1, 0],
 ['note_on', 0, 1, 25, 96],
 ['note_off', 192, 0, 1, 0],

here is the corresponding score sctructure:

 ['text_event', 0, 'www.ely.anglican.org/parishes/camgsm/chimes.html'],
 ['text_event', 0, 'Lord through this hour/ be Thou our guide'],
 ['text_event', 0, 'so, by Thy power/ no foot shall slide'],
 ['patch_change', 0, 1, 8],
 ['note', 0, 96, 1, 25, 96],
 ['note', 96, 96, 1, 29, 96],
 ['note', 192, 96, 1, 27, 96],
 ['note', 288, 192, 1, 20, 96],
 ['note', 480, 96, 1, 25, 96],
 ['note', 576, 96, 1, 27, 96],
 ['note', 672, 96, 1, 29, 96],
 ['note', 768, 192, 1, 25, 96],
 ['note', 960, 96, 1, 29, 96],
 ['note', 1056, 96, 1, 25, 96],
 ['note', 1152, 96, 1, 27, 96],
 ['note', 1248, 192, 1, 20, 96],
 ['note', 1440, 96, 1, 20, 96],
 ['note', 1536, 96, 1, 27, 96],
 ['note', 1632, 96, 1, 29, 96],
 ['note', 1728, 192, 1, 25, 96]

Note also that scores aren't crucially ordered.  So this:

 ['note', 768, 192, 1, 25, 96],
 ['note', 960, 96, 1, 29, 96],
 ['note', 1056, 96, 1, 25, 96],

means the same thing as:

 ['note', 960, 96, 1, 29, 96],
 ['note', 768, 192, 1, 25, 96],
 ['note', 1056, 96, 1, 25, 96],

The only exception to this is in the case of things like:

 ['patch_change', 200,     2, 15],
 ['note',         200, 96, 2, 25, 96],

where two (or more) score items happen I<at the same time> and where one
affects the meaning of the other.

=head1 WHAT CAN BE IN A SCORE

Besides the new score structure item C<note> (covered above),
the possible contents of a score structure can be summarized thus:
Whatever can appear in an event structure can appear in a score
structure, save that its second parameter denotes not a
delta-time in ticks, but instead denotes the absolute number of ticks
from the start of the track.

To avoid the long periphrase "items in a score structure", I will
occasionally refer to items in a score structure as "notes", whether or
not they are actually C<note> commands.  This leaves "event" to
unambiguously denote items in an event structure.

These, below, are all the items that can appear in a score.
This is basically just a repetition of the table in
L<MIDI::Event>, with starttime substituting for dtime --
so refer to L<MIDI::Event> for an explanation of what the data types
(like "velocity" or "pitch_wheel").
As far as order, the first items are generally the most important:

=over

=item ('note', I<starttime>, I<duration>, I<channel>, I<note>, I<velocity>)

=item ('key_after_touch', I<starttime>, I<channel>, I<note>, I<velocity>)

=item ('control_change', I<starttime>, I<channel>, I<controller(0-127)>, I<value(0-127)>)

=item ('patch_change', I<starttime>, I<channel>, I<patch>)

=item ('channel_after_touch', I<starttime>, I<channel>, I<velocity>)

=item ('pitch_wheel_change', I<starttime>, I<channel>, I<pitch_wheel>)

=item ('set_sequence_number', I<starttime>, I<sequence>)

=item ('text_event', I<starttime>, I<text>)

=item ('copyright_text_event', I<starttime>, I<text>)

=item ('track_name', I<starttime>, I<text>)

=item ('instrument_name', I<starttime>, I<text>)

=item ('lyric', I<starttime>, I<text>)

=item ('marker', I<starttime>, I<text>)

=item ('cue_point', I<starttime>, I<text>)

=item ('text_event_08', I<starttime>, I<text>)

=item ('text_event_09', I<starttime>, I<text>)

=item ('text_event_0a', I<starttime>, I<text>)

=item ('text_event_0b', I<starttime>, I<text>)

=item ('text_event_0c', I<starttime>, I<text>)

=item ('text_event_0d', I<starttime>, I<text>)

=item ('text_event_0e', I<starttime>, I<text>)

=item ('text_event_0f', I<starttime>, I<text>)

=item ('end_track', I<starttime>)

=item ('set_tempo', I<starttime>, I<tempo>)

=item ('smpte_offset', I<starttime>, I<hr>, I<mn>, I<se>, I<fr>, I<ff>)

=item ('time_signature', I<starttime>, I<nn>, I<dd>, I<cc>, I<bb>)

=item ('key_signature', I<starttime>, I<sf>, I<mi>)

=item ('sequencer_specific', I<starttime>, I<raw>)

=item ('raw_meta_event', I<starttime>, I<command>(0-255), I<raw>)

=item ('sysex_f0', I<starttime>, I<raw>)

=item ('sysex_f7', I<starttime>, I<raw>)

=item ('song_position', I<starttime>)

=item ('song_select', I<starttime>, I<song_number>)

=item ('tune_request', I<starttime>)

=item ('raw_data', I<starttime>, I<raw>)

=back


=head1 FUNCTIONS

This module provides these functions:

=over

=item $score2_r = MIDI::Score::copy_structure($score_r)

This takes a I<reference> to a score structure, and returns a
I<reference> to a copy of it. Example usage:

          @new_score = @{ MIDI::Score::copy_structure( \@old_score ) };

=item $events_r = MIDI::Score::score_r_to_events_r( $score_r )

=item ($events_r, $ticks) = MIDI::Score::score_r_to_events_r( $score_r )

This takes a I<reference> to a score structure, and converts it to an
event structure, which it returns a I<reference> to.  In list context,
also returns a second value, a count of the number of ticks that
structure takes to play (i.e., the end-time of the temporally last
item).

=item $score2_r = MIDI::Score::sort_score_r( $score_r)

This takes a I<reference> to a score structure, and returns a
I<reference> to a sorted (by time) copy of it. Example usage:

          @sorted_score = @{ MIDI::Score::sort_score_r( \@old_score ) };

=item $score_r = MIDI::Score::events_r_to_score_r( $events_r )

=item ($score_r, $ticks) = MIDI::Score::events_r_to_score_r( $events_r )

This takes a I<reference> to an event structure, converts it to a
score structure, which it returns a I<reference> to.  If called in
list context, also returns a count of the number of ticks that
structure takes to play (i.e., the end-time of the temporally last
item).

=item $ticks = MIDI::Score::score_r_time( $score_r )

This takes a I<reference> to a score structure, and returns
a count of the number of ticks that structure takes to play
(i.e., the end-time of the temporally last item).

=item MIDI::Score::dump_score( $score_r )

This dumps (via C<print>) a text representation of the contents of
the event structure you pass a reference to.

=back

=head1 COPYRIGHT 

Copyright (c) 1998-2002 Sean M. Burke. All rights reserved.

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=head1 AUTHOR

Sean M. Burke C<sburke@cpan.org>
