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Fix: Original music playback rate was slightly too fast

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Found a new tempo value experimentally. The new value gives a timing error of less than 0.01 second per minute.
This commit is contained in:
Niels Martin Hansen 2022-01-25 21:18:17 +01:00
parent 81adc38176
commit 41c40f130b
1 changed files with 5 additions and 4 deletions
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9
src/music/midifile.cpp
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@ -525,8 +525,8 @@ struct MpsMachine {
Channel channels[16]; ///< playback status for each MIDI channel
std::vector<uint32> segments; ///< pointers into songdata to repeatable data segments
int16 tempo_ticks; ///< ticker that increments when playing a frame, decrements before playing a frame
int16 current_tempo; ///< threshold for actually playing a frame
int16 initial_tempo; ///< starting tempo of song
int16 current_tempo; ///< threshold for actually playing a frame
int16 initial_tempo; ///< starting tempo of song
bool shouldplayflag; ///< not-end-of-song flag
static const int TEMPO_RATE;
@ -787,10 +787,11 @@ struct MpsMachine {
bool PlayInto()
{
/* Tempo seems to be handled as TEMPO_RATE = 148 ticks per second.
* Use this as the tickdiv, and define the tempo to be one second (1M microseconds) per tickdiv.
* Use this as the tickdiv, and define the tempo to be somewhat less than one second (1M microseconds) per quarter note.
* This value was found experimentally to give a very close approximation of the correct playback speed.
* MIDI software loading exported files will show a bogus tempo, but playback will be correct. */
this->target.tickdiv = TEMPO_RATE;
this->target.tempos.push_back(MidiFile::TempoChange(0, 1000000));
this->target.tempos.push_back(MidiFile::TempoChange(0, 980500));
/* Initialize playback simulation */
this->RestartSong();