mirror of
https://github.com/cookiengineer/audacity
synced 2025-05-04 17:49:45 +02:00
125 lines
3.2 KiB
C
125 lines
3.2 KiB
C
/* tempomap.c -- used by midifile reader to record and lookup time maps */
|
|
/*
|
|
* This module is designed to provide tempo change list insert and
|
|
* lookup facilities. The exact interpretation of beat and tempo are
|
|
* defined in one function, elapsed_time, which takes a tempo and a
|
|
* number of beats, and returns time.
|
|
*/
|
|
|
|
#include "cext.h"
|
|
#include "midifns.h"
|
|
#include "timebase.h"
|
|
#include "moxc.h"
|
|
#include "seq.h"
|
|
#include "tempomap.h"
|
|
|
|
static time_type elapsed_time();
|
|
|
|
/* tempomap_create -- create a tempomap */
|
|
/**/
|
|
tempomap_type tempomap_create()
|
|
{
|
|
tempochange_type tempochange = tempochange_alloc();
|
|
tempomap_type tempomap = tempomap_alloc();
|
|
tempomap->hint = tempomap->entries = tempochange;
|
|
tempochange->beat = 0L;
|
|
/* default tempo is 120 (= 50000microsec/beat) and 24 divisions/quarter */
|
|
/* this may be overridden by a tempomap_insert */
|
|
tempochange->tempo = 500000L / 24;
|
|
tempochange->rtime = 0L;
|
|
tempochange->next = NULL;
|
|
return tempomap;
|
|
}
|
|
|
|
|
|
/* tempomap_free -- deallocate storage for tempo map */
|
|
/**/
|
|
void tempomap_free(tm)
|
|
tempomap_type tm;
|
|
{
|
|
while (tm->entries) {
|
|
tempochange_type tc = tm->entries;
|
|
tm->entries = tc->next;
|
|
tempochange_free(tc);
|
|
}
|
|
memfree(tm, sizeof(tempomap_node));
|
|
}
|
|
|
|
|
|
/* tempomap_insert -- insert a tempo change into the map */
|
|
/**/
|
|
void tempomap_insert(tempomap, beat, tempo)
|
|
tempomap_type tempomap;
|
|
long beat; /* beat division number */
|
|
long tempo; /* microseconds per beat division */
|
|
{
|
|
tempochange_type tempochange = tempochange_alloc();
|
|
register tempochange_type prev;
|
|
register tempochange_type next;
|
|
|
|
tempochange->tempo = tempo;
|
|
tempochange->beat = beat;
|
|
|
|
if ((!(tempomap->hint->next)) ||
|
|
(tempomap->hint->beat > beat))
|
|
tempomap->hint = tempomap->entries;
|
|
|
|
/* find the insert point */
|
|
for (prev = tempomap->hint;
|
|
(next = prev->next) && (next->beat <= beat);
|
|
prev = next);
|
|
|
|
/* make the insert */
|
|
tempochange->next = next;
|
|
prev->next = tempochange;
|
|
tempomap->hint = prev;
|
|
|
|
/* update the real time of each change */
|
|
for (tempochange = prev;
|
|
tempochange->next;
|
|
tempochange = tempochange->next) {
|
|
tempochange->next->rtime =
|
|
tempochange->rtime +
|
|
elapsed_time(tempochange->tempo,
|
|
tempochange->next->beat - tempochange->beat);
|
|
}
|
|
}
|
|
|
|
|
|
/* tempomap_lookup -- convert beat to 4us time */
|
|
/*
|
|
* The returned time is real time in units of 4us.
|
|
*/
|
|
time_type tempomap_lookup(tempomap, beat)
|
|
tempomap_type tempomap;
|
|
long beat;
|
|
{
|
|
register tempochange_type prev;
|
|
register tempochange_type next;
|
|
|
|
if ((!(tempomap->hint->next)) ||
|
|
(tempomap->hint->beat > beat))
|
|
tempomap->hint = tempomap->entries;
|
|
|
|
/* find the last inflection point */
|
|
for (prev = tempomap->hint;
|
|
(next = prev->next) && (next->beat <= beat);
|
|
prev = next);
|
|
|
|
/* interpolate */
|
|
return prev->rtime +
|
|
elapsed_time(prev->tempo, beat - prev->beat);
|
|
}
|
|
|
|
|
|
/* elapsed_time -- compute the real elapsed time at a given tempo */
|
|
/*
|
|
* the time returned is in units of 4us.
|
|
*/
|
|
static time_type elapsed_time(tempo, beat)
|
|
long tempo;
|
|
long beat;
|
|
{
|
|
return (time_type)((tempo * beat) >> 2);
|
|
}
|