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| author | Simon Howard | 2014-10-14 22:59:42 -0400 |
|---|---|---|
| committer | Simon Howard | 2014-10-14 22:59:42 -0400 |
| commit | c7e82b3866134277e73f9a9d2b0f67da3fa403d0 (patch) | |
| tree | 512f4f70bdc3516abc5ed0f4d7c1402353c25a24 /src | |
| parent | 77d7e984d19f52215bf22df95358ef41dda1e430 (diff) | |
| download | chocolate-doom-c7e82b3866134277e73f9a9d2b0f67da3fa403d0.tar.gz chocolate-doom-c7e82b3866134277e73f9a9d2b0f67da3fa403d0.tar.bz2 chocolate-doom-c7e82b3866134277e73f9a9d2b0f67da3fa403d0.zip | |
Fix OPL MIDI tempo calculations.
It turns out that the way that tempo has been calculated in OPL playback
has been broken for a long time. The mysterious "fudge factor" that I
had to apply to tempo calculations is actually completely unnecessary:
the byte-swapping in the MIDI_GetFileTimeDivision() function was being
done wrong, so the time division being used by the OPL MIDI code was
completely wrong. Presumably the multiply by 260 was close enough to an
8-bit bitshift that it worked okayish, but large enough time division
values would overflow a single byte and screw up.
This fixes long-running OPL playback problems in a number of WADs, most
notably Alien Vendetta. This *really* fixes #352.
Diffstat (limited to 'src')
| -rw-r--r-- | src/i_oplmusic.c | 6 | ||||
| -rw-r--r-- | src/midifile.c | 6 |
2 files changed, 4 insertions, 8 deletions
diff --git a/src/i_oplmusic.c b/src/i_oplmusic.c index bcc8fe68..a1e90506 100644 --- a/src/i_oplmusic.c +++ b/src/i_oplmusic.c @@ -46,9 +46,6 @@ #define PERCUSSION_LOG_LEN 16 -// TODO: Figure out why this is needed. -#define TEMPO_FUDGE_FACTOR 260 - typedef struct { byte tremolo; @@ -1198,8 +1195,7 @@ static void ScheduleTrack(opl_track_data_t *track) // Get the number of microseconds until the next event. nticks = MIDI_GetDeltaTime(track->iter); - us = ((uint64_t) nticks * us_per_beat * TEMPO_FUDGE_FACTOR) - / ticks_per_beat; + us = ((uint64_t) nticks * us_per_beat) / ticks_per_beat; // Set a timer to be invoked when the next event is // ready to play. diff --git a/src/midifile.c b/src/midifile.c index 94ec4441..92ffd803 100644 --- a/src/midifile.c +++ b/src/midifile.c @@ -699,14 +699,14 @@ int MIDI_GetNextEvent(midi_track_iter_t *iter, midi_event_t **event) unsigned int MIDI_GetFileTimeDivision(midi_file_t *file) { - short result = SHORT(file->header.time_division); + short result = SDL_SwapBE16(file->header.time_division); // Negative time division indicates SMPTE time and must be handled // differently. if (result < 0) { - // TODO: Figure this out. - return 96; + return (signed int)(-(result/256)) + * (signed int)(result & 0xFF); } else { |