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Generalise the timing

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Michael Hayes 14 years ago
parent be813dcb55
commit 5c0c1fba18
2 changed files with 62 additions and 38 deletions
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92
extra/mmelody.c
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@ -68,45 +68,76 @@
* sixteenth notes? Perhaps A,,
* Perhaps lower case for eighth notes.
* Perhaps lower case for eighth notes?
* Triplets and other irrational tuplets? A triplet quarter note
has 2 / 3 the duration of a quarter note while a triplet eighth note
has 2 / 3 the duration of of an eighth note. This can be achieved
using *6 or *12.
*/
enum {MMELODY_SCALE_SIZE = 12};
/* Assume each beat is a quarter note. */
enum {MMELODY_BEAT_FRACTION = 4};
/* Scale factor for fraction of a symbol timing. */
enum {MMELODY_DURATION_FRACTION = 4};
/* How long to release note before sounding the next one. */
#define MMELODY_RELEASE_MS 50
static void
mmelody_ticker_set (mmelody_t mmelody)
{
uint16_t speed;
/* The duration of a beat varies with the time signature:
2/2 : minum (half note)
4/4 : crotchet (quarter note)
6/8, 9/8, 12/8 : dotted crotchet (one and a half quarter notes)
Currently, there is no time signature support so we assume 4/4.
This means a beat is a quarter note and a bar is four quarter
notes.
ticks_per_beat = poll_rate * 60 / speed
symbols_per_beat = symbol_fraction / MMELODY_BEAT_FRACTION
ticks_per_symbol = ticks_per_beat / symbols_per_beat
ticks_per_unit = ticks_per_symbol / MMELODY_DURATION_FRACTION
/* Notes per four minutes. */
speed = mmelody->speed * mmelody->note_fraction;
ticks_per_note = ticks_per_beat * MMELODY_BEAT_FRACTION
= ticks_per_unit * symbol_fraction
* MMELODY_DURATION_FRACTION
/* This is the duration of an eighth-note.
The duration is specified as the actual duration scaled by
MMELODY_DURATION_FRACTION so that it can specify half periods.
With note_fraction = 4, speed = 50, and poll_rate of 200 this
gives a result of 120. */
mmelody->note_ticks = mmelody->poll_rate * 60 * 2 / speed;
With symbol_fraction = 4, speed = 50, and poll_rate of 200 this
gives a result of 60. */
mmelody->unit_ticks = (mmelody->poll_rate * 60
* MMELODY_BEAT_FRACTION)
/ (mmelody->speed * mmelody->symbol_fraction
* MMELODY_DURATION_FRACTION);
}
static void
mmelody_note_on (mmelody_t mmelody, mmelody_note_t note, uint8_t duration)
{
/* The duration is in terms of eighth notes. */
/* The duration is in terms of the half the duration of a symbol. */
mmelody->play_callback (mmelody->play_callback_data, note,
mmelody->volume);
mmelody->note = note;
/* Determine ticks between sounding notes (this needs to be a
minimum of 1). */
mmelody->ticks2 = mmelody->note_ticks / 16;
if (!mmelody->ticks2)
mmelody->ticks2 = 1;
minimum of 1). If we assume a release period of 50 ms,
this will give a count of 10 ticks at 200 Hz sampling. */
mmelody->ticks2 = mmelody->release_ticks;
/* Determine ticks before turning the note off. */
mmelody->ticks1 = mmelody->note_ticks * duration - mmelody->ticks2;
mmelody->ticks1 = mmelody->unit_ticks * duration - mmelody->ticks2;
}
@ -122,9 +153,9 @@ mmelody_note_off (mmelody_t mmelody)
/* Specify the default note length in fractions of a measure (bar).
A value of 4 is the default which makes each note a quarter note. */
static void
mmelody_note_fraction_set (mmelody_t mmelody, uint8_t note_fraction)
mmelody_symbol_fraction_set (mmelody_t mmelody, uint8_t symbol_fraction)
{
mmelody->note_fraction = note_fraction;
mmelody->symbol_fraction = symbol_fraction;
mmelody_ticker_set (mmelody);
}
@ -222,7 +253,7 @@ mmelody_scan (mmelody_t mmelody, const char *str)
case '*':
if (num)
mmelody_note_fraction_set (mmelody, num);
mmelody_symbol_fraction_set (mmelody, num);
continue;
case '@':
@ -262,22 +293,20 @@ mmelody_scan (mmelody_t mmelody, const char *str)
duration++;
str++;
}
duration = duration * MMELODY_DURATION_FRACTION;
if (*str == '.')
{
/* Dotted quarter note. */
duration += duration * 2;
duration += duration / 2;
str++;
}
else if (*str == ',')
{
/* Eighth note. */
str++;
/* What about dotted eighth notes? */
}
else
{
/* Quarter note. */
duration *= 2;
duration = duration / 2;
}
mmelody_note_on (mmelody, note, duration);
@ -301,7 +330,7 @@ mmelody_play (mmelody_t mmelody, const char *str)
mmelody->loop_count = 0;
mmelody->octave = MMELODY_OCTAVE_DEFAULT;
/* Default to quarter notes. */
mmelody_note_fraction_set (mmelody, 4);
mmelody_symbol_fraction_set (mmelody, 4);
/* Stop what is currently sounding. */
mmelody_note_off (mmelody);
@ -317,16 +346,8 @@ mmelody_speed_set (mmelody_t mmelody, mmelody_speed_t speed)
/* With 8 bits for the tempo (in bpm), the max tempo is 255 bpm.
This corresponds to 4.25 beats per second. If the minimum time
to release a note is 1 / 8 of a quarter note, then we need to
poll at a rate of at least 4.25 * 8 = 34 times per second.
poll at a rate of at least 4.25 * 8 = 34 times per second. */
The duration of a beat varies with the time signature:
2/2 : minum (half note)
4/4 : crotchet (quarter note)
6/8, 9/8, 12/8 : dotted crotchet (one and a half quarter notes)
Currently, there is no time signature support so we assume 4/4.
This means a beat is quarter note and a bar is four quarter notes.
*/
mmelody->speed = speed;
mmelody_ticker_set (mmelody);
}
@ -384,8 +405,9 @@ mmelody_init (mmelody_obj_t *mmelody,
mmelody->note = 0;
mmelody->ticks1 = 0;
mmelody->ticks2 = 0;
mmelody->release_ticks = (poll_rate * MMELODY_RELEASE_MS) / 1000;
mmelody_speed_set (mmelody, MMELODY_SPEED_DEFAULT);
mmelody_note_fraction_set (mmelody, 4);
mmelody_symbol_fraction_set (mmelody, 4);
return mmelody;
}

8
extra/mmelody.h
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@ -22,15 +22,17 @@ typedef struct
{
uint16_t ticks1;
uint8_t ticks2;
/* Duration of an eighth note. */
uint8_t note_ticks;
uint8_t unit_ticks;
uint8_t release_ticks;
/* Pointer to current position in string. */
const char *cur;
/* Pointer to start of string. */
const char *start;
const char *loop_start;
int8_t loop_count;
uint8_t note_fraction;
/* Fraction of a whole note, e.g., 4 for quarter note. */
uint8_t symbol_fraction;
/* Last note emitted. */
uint8_t note;
/* Tempo in beats per minute. */
mmelody_speed_t speed;

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