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@ -20,62 +20,55 @@
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C5? This uses numbers to indicate note duration, for example, C2
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denotes a C of twice the standard duration.
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For emphasis of first beat in bar, perhaps use ^ to indicate
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louder, for example, C^. Similarly, to make a note quieter it
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could have a v suffix. Alternatively, | bar markers could be
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inserted and perhaps time signatures.
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By default notes are quarter-notes. It is probably best to define
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speed in terms of quarter-notes (beats per minute) rather than bars
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per minute since this requires bars to be defined. Two bars in 4/4
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could be represented by C^DEDC^BAB whereas two bars in 3/4 could be
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represented by C^DEC^DE.
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By default notes are crotchets (quarter notes) and tempos are
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defined in beats per minute. If we assume 4/4 time, then each beat
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has a quarter-note duration.
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The note duration can be halved with a comma suffix, e.g., A,
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The note duration can be extended by a half with a dot suffix, e.g., A.
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The note duration can be doubled with a slash suffix, e.g., A/
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The note duration can be trebled with two slash suffixes, e.g., A//
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(this can be continued to lengthen the note).
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If there are lots of quavers (eighth notes), then the default note
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duration can be switched using *8. *4 returns to quarter note timing.
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Rests are specified with a space character. The timing modifiers ,
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. and / can be used.
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<ABC> is equivalent to ABCABC
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<ABC>3 is equivalent to ABCABCABC
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So how should we denote note duration? We need to distinguish
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between 2 identical quarter-notes (A A) played in succession and a
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half-note since this sounds different.
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We could use AA to indicate two A quarter-notes. Alternatively, we
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could use AA to indicate an A half-note. However, for a whole note
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we would need to indicate this with AAAA. With the latter scheme
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we could separate two indentical quarter notes with a comma, for
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example, A,A.
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Eighth notes and triplets? *8 switches to interpreting the notes
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as eighth notes. *4 switches back to quarter notes.
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Rests are easy. Each space represents one rest of quarter-note
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duration. Two spaces represent a half-note rest. Alternatively,
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we could represent this with " /".
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From a sequencing point of view it is simpler if every symbol
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represents a quarter-note rather than having variable length notes
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since this alters the sequencing timing. This favours the approach
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of using AA to denote a half-note.
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If I implement a simple attack/decay response then it would be
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easier to use A/ for a half-note since we would interpret the / as
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to keep playing the previous note without sounding it again.
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Alternatively, when each new note is sounded there could be a short
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delay.
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>num could indicate jump forward to label num while <num could
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represent jump back to label num. Although I prefer the notation
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<ABC>3 to represent playing the notes ABC in succession 3 times.
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This notation could be nested, for example, <ABC<DEF>2>3.
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Perhaps <ABC> denotes playing ABC indefinitely? No I prefer
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a simple repeat. Use ABC: for an infinite repeat.
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ABC: performs an infinite repeat of ABC
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<ABC]1DE]2FG> represents ABCDEABCFG where ]n denotes alternate
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endings.
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With 8 bits for the tempo (in bpm), the max tempo is 255 bpm.
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This corresponds to 4.25 beats per second. If the minimum time
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to release a note is 1 / 8 of a quarter note, then we need
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to poll at a rate of at least 4.25 * 8 = 34 times per second.
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A+ sounds an octave higher
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A- sounds an octave lower
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@120 sets the tempo to 120 beats per minute
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This could be made a lot more flexible but the orginal
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implementation had a tight memory constraint.
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implementation had a tight memory constraint. Possible extensions:
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* For emphasis perhaps use ^ to indicate louder, for example, C^.
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Similarly, to make a note quieter it could have a v suffix.
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* Use | for bar markers; these can be ignored.
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* Time signatures.
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* Nested loops, e.g., <AB<ABC>>
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* sixteenth notes? Perhaps A,,
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* Perhaps lower case for eighth notes.
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*/
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enum {MMELODY_SCALE_SIZE = 12};
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@ -89,22 +82,31 @@ mmelody_ticker_set (mmelody_t mmelody)
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/* Notes per four minutes. */
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speed = mmelody->speed * mmelody->note_fraction;
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mmelody->beat_duration = mmelody->poll_rate * 60 * 4 / speed;
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/* This is the duration of an eighth-note.
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With note_fraction = 4, speed = 50, and poll_rate of 200 this
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gives a result of 120. */
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mmelody->note_ticks = mmelody->poll_rate * 60 * 2 / speed;
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}
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static void
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mmelody_note_on (mmelody_t mmelody, mmelody_note_t note, uint8_t duration)
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{
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/* The duration is in terms of eighth notes. */
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mmelody->play_callback (mmelody->play_callback_data, note,
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mmelody->volume);
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mmelody->note = note;
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/* Determine ticks between sounding notes. */
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mmelody->ticks2 = (mmelody->beat_duration + 8) / 16;
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/* Determine ticks between sounding notes (this needs to be a
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minimum of 1). */
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mmelody->ticks2 = mmelody->note_ticks / 16;
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if (!mmelody->ticks2)
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mmelody->ticks2 = 1;
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/* Determine ticks before turning the note off. */
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mmelody->ticks1 = mmelody->beat_duration * duration - mmelody->ticks2;
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mmelody->ticks1 = mmelody->note_ticks * duration - mmelody->ticks2;
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}
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@ -148,7 +150,7 @@ mmelody_scan (mmelody_t mmelody, const char *str)
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char modifier;
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bool have_hash;
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bool have_num;
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mmelody_note_t note;
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mmelody_note_t note = 0;
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uint8_t duration = 1;
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/* Play rest at end of melody. */
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@ -218,17 +220,6 @@ mmelody_scan (mmelody_t mmelody, const char *str)
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str++;
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continue;
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/* Play rest. */
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case ' ':
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while (*str == '/')
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{
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duration++;
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str++;
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}
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mmelody_note_on (mmelody, 0, duration);
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return str;
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break;
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case '*':
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if (num)
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mmelody_note_fraction_set (mmelody, num);
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@ -263,11 +254,31 @@ mmelody_scan (mmelody_t mmelody, const char *str)
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/* Convert note to MIDI note number. */
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note += (mmelody->octave + 1) * MMELODY_SCALE_SIZE;
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/* Fall through. */
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case ' ':
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while (*str == '/')
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{
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duration++;
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str++;
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}
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if (*str == '.')
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{
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/* Dotted quarter note. */
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duration += duration * 2;
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str++;
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}
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else if (*str == ',')
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{
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/* Eighth note. */
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str++;
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/* What about dotted eighth notes? */
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}
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else
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{
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/* Quarter note. */
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duration *= 2;
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}
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mmelody_note_on (mmelody, note, duration);
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return str;
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@ -303,7 +314,12 @@ mmelody_play (mmelody_t mmelody, const char *str)
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void
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mmelody_speed_set (mmelody_t mmelody, mmelody_speed_t speed)
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{
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/* The duration of a beat varies with the time signature:
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/* With 8 bits for the tempo (in bpm), the max tempo is 255 bpm.
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This corresponds to 4.25 beats per second. If the minimum time
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to release a note is 1 / 8 of a quarter note, then we need to
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poll at a rate of at least 4.25 * 8 = 34 times per second.
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The duration of a beat varies with the time signature:
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2/2 : minum (half note)
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4/4 : crotchet (quarter note)
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6/8, 9/8, 12/8 : dotted crotchet (one and a half quarter notes)
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@ -365,11 +381,11 @@ mmelody_init (mmelody_obj_t *mmelody,
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mmelody->play_callback = play_callback;
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mmelody->play_callback_data = play_callback_data;
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mmelody->volume = 100;
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mmelody->note_fraction = 1;
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mmelody->note = 0;
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mmelody->ticks1 = 0;
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mmelody->ticks2 = 0;
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mmelody_speed_set (mmelody, MMELODY_SPEED_DEFAULT);
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mmelody_note_fraction_set (mmelody, 4);
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return mmelody;
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}
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Michael Hayes
14 years ago