raze-gles/polymer/eduke32/source/midi.c

//-------------------------------------------------------------------------
/*
Copyright (C) 2016 EDuke32 developers and contributors

This file is part of EDuke32.

EDuke32 is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License version 2
as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/
//-------------------------------------------------------------------------

#include <stdlib.h>
#include <string.h>
#include "standard.h"
#include "music.h"
#include "_midi.h"
#include "midi.h"
#include "mpu401.h"
#include "compat.h"
#include "pragmas.h"

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

extern int32_t MUSIC_SoundDevice;

static const int32_t _MIDI_CommandLengths[ NUM_MIDI_CHANNELS ] =
{
    0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 1, 1, 2, 0
};

static track *_MIDI_TrackPtr = NULL;
static int32_t    _MIDI_TrackMemSize;
static int32_t    _MIDI_NumTracks;

static int32_t _MIDI_SongActive = FALSE;
static int32_t _MIDI_SongLoaded = FALSE;
static int32_t _MIDI_Loop = FALSE;

static int32_t  _MIDI_Division;
static int32_t  _MIDI_Tick    = 0;
static int32_t  _MIDI_Beat    = 1;
static int32_t  _MIDI_Measure = 1;
static uint32_t _MIDI_Time;
static int32_t  _MIDI_BeatsPerMeasure;
static int32_t  _MIDI_TicksPerBeat;
static int32_t  _MIDI_TimeBase;
static int32_t _MIDI_FPSecondsPerTick;
static uint32_t _MIDI_TotalTime;
static int32_t  _MIDI_TotalTicks;
static int32_t  _MIDI_TotalBeats;
static int32_t  _MIDI_TotalMeasures;

uint32_t _MIDI_PositionInTicks;
uint32_t _MIDI_GlobalPositionInTicks;

static int32_t  _MIDI_Context;

static int32_t _MIDI_ActiveTracks;
static int32_t _MIDI_TotalVolume = MIDI_MaxVolume;

static int32_t _MIDI_ChannelVolume[ NUM_MIDI_CHANNELS ];

static midifuncs *_MIDI_Funcs = NULL;

static int32_t Reset = FALSE;

int32_t MIDI_Tempo = 120;

char MIDI_PatchMap[ 128 ];


/**********************************************************************

   Memory locked functions:

**********************************************************************/


/*---------------------------------------------------------------------
   Function: _MIDI_ReadNumber

   Reads a variable length number from a MIDI track.
---------------------------------------------------------------------*/

static int32_t _MIDI_ReadNumber(void *from, size_t size)
{
    if (size > 4)
        size = 4;

    char *FromPtr = (char *)from;

    int32_t value = 0;

    do
    {
        value <<= 8;
        value += *FromPtr++;
    } while (size--);

    return value;
}


/*---------------------------------------------------------------------
   Function: _MIDI_ReadDelta

   Reads a variable length encoded delta delay time from the MIDI data.
---------------------------------------------------------------------*/

static int32_t _MIDI_ReadDelta(track *ptr)
{
    int32_t          value;

    GET_NEXT_EVENT(ptr, value);

    if (value & 0x80)
    {
        value &= 0x7f;

        char c;
        do
        {
            GET_NEXT_EVENT(ptr, c);
            value = (value << 7) + (c & 0x7f);
        }
        while (c & 0x80);
    }

    return value;
}


/*---------------------------------------------------------------------
   Function: _MIDI_ResetTracks

   Sets the track pointers to the beginning of the song.
---------------------------------------------------------------------*/

static void _MIDI_ResetTracks(void)
{
    _MIDI_Tick = 0;
    _MIDI_Beat = 1;
    _MIDI_Measure = 1;
    _MIDI_Time = 0;
    _MIDI_BeatsPerMeasure = 4;
    _MIDI_TicksPerBeat = _MIDI_Division;
    _MIDI_TimeBase = 4;

    _MIDI_PositionInTicks = 0;
    //_MIDI_GlobalPositionInTicks = 0;
    _MIDI_ActiveTracks    = 0;
    _MIDI_Context         = 0;

    track *ptr = _MIDI_TrackPtr;

    for (int i = 0; i < _MIDI_NumTracks; i++)
    {
        ptr->pos                    = ptr->start;
        ptr->delay                  = _MIDI_ReadDelta(ptr);
        ptr->active                 = ptr->EMIDI_IncludeTrack;
        ptr->RunningStatus          = 0;
        ptr->currentcontext         = 0;
        ptr->context[ 0 ].loopstart = ptr->start;
        ptr->context[ 0 ].loopcount = 0;

        if (ptr->active)
            _MIDI_ActiveTracks++;

        ptr++;
    }
}


/*---------------------------------------------------------------------
   Function: _MIDI_AdvanceTick

   Increment tick counters.
---------------------------------------------------------------------*/

static void _MIDI_AdvanceTick(void)
{
    _MIDI_PositionInTicks++;
    _MIDI_Time += _MIDI_FPSecondsPerTick;

    while (++_MIDI_Tick > _MIDI_TicksPerBeat)
    {
        _MIDI_Tick -= _MIDI_TicksPerBeat;
        _MIDI_Beat++;
    }

    while (_MIDI_Beat > _MIDI_BeatsPerMeasure)
    {
        _MIDI_Beat -= _MIDI_BeatsPerMeasure;
        _MIDI_Measure++;
    }
}


/*---------------------------------------------------------------------
   Function: _MIDI_SysEx

   Interpret SysEx Event.
---------------------------------------------------------------------*/

static void _MIDI_SysEx(track *Track)
{
    int32_t const length = _MIDI_ReadDelta(Track);
    Track->pos += length;
}


/*---------------------------------------------------------------------
   Function: _MIDI_MetaEvent

   Interpret Meta Event.
---------------------------------------------------------------------*/

static void _MIDI_MetaEvent(track *Track)
{
    int32_t   command;
    int32_t   length;

    GET_NEXT_EVENT(Track, command);
    GET_NEXT_EVENT(Track, length);

    switch (command)
    {
    case MIDI_END_OF_TRACK :
        Track->active = FALSE;

        _MIDI_ActiveTracks--;
        break;

    case MIDI_TEMPO_CHANGE :
        MIDI_SetTempo(
            tabledivide32_noinline(60000000L, _MIDI_ReadNumber(Track->pos, 3)));
        break;

    case MIDI_TIME_SIGNATURE :
    {
        if ((_MIDI_Tick > 0) || (_MIDI_Beat > 1))
            _MIDI_Measure++;

        _MIDI_Tick = 0;
        _MIDI_Beat = 1;

        _MIDI_BeatsPerMeasure = (int32_t) *Track->pos;
        int32_t denominator = (int32_t) *(Track->pos + 1);
        _MIDI_TimeBase = 1;

        while (denominator > 0)
        {
            _MIDI_TimeBase += _MIDI_TimeBase;
            denominator--;
        }
        _MIDI_TicksPerBeat = tabledivide32_noinline(_MIDI_Division * 4, _MIDI_TimeBase);
        break;
    }
    }

    Track->pos += length;
}


/*---------------------------------------------------------------------
   Function: _MIDI_InterpretControllerInfo

   Interprets the MIDI controller info.
---------------------------------------------------------------------*/

static int32_t _MIDI_InterpretControllerInfo(track *Track, int32_t TimeSet, int32_t channel, int32_t c1, int32_t c2)
{
    track *trackptr;
    int32_t tracknum;
    int32_t loopcount;

    switch (c1)
    {
    case MIDI_MONO_MODE_ON :
        Track->pos++;
        break;

    case MIDI_VOLUME :
        if (!Track->EMIDI_VolumeChange)
            _MIDI_SetChannelVolume(channel, c2);
        break;

    case EMIDI_INCLUDE_TRACK :
    case EMIDI_EXCLUDE_TRACK :
        break;

    case EMIDI_PROGRAM_CHANGE :
        if (Track->EMIDI_ProgramChange)
            _MIDI_Funcs->ProgramChange(channel, MIDI_PatchMap[ c2 & 0x7f ]);
        break;

    case EMIDI_VOLUME_CHANGE :
        if (Track->EMIDI_VolumeChange)
            _MIDI_SetChannelVolume(channel, c2);
        break;

    case EMIDI_CONTEXT_START :
        break;

    case EMIDI_CONTEXT_END :
        if ((Track->currentcontext == _MIDI_Context) || (_MIDI_Context < 0) ||
            (Track->context[_MIDI_Context].pos == NULL))
            break;

        Track->currentcontext = _MIDI_Context;
        Track->context[ 0 ].loopstart = Track->context[ _MIDI_Context ].loopstart;
        Track->context[ 0 ].loopcount = Track->context[ _MIDI_Context ].loopcount;
        Track->pos           = Track->context[ _MIDI_Context ].pos;
        Track->RunningStatus = Track->context[ _MIDI_Context ].RunningStatus;

        if (TimeSet)
            break;

        _MIDI_Time             = Track->context[ _MIDI_Context ].time;
        _MIDI_FPSecondsPerTick = Track->context[ _MIDI_Context ].FPSecondsPerTick;
        _MIDI_Tick             = Track->context[ _MIDI_Context ].tick;
        _MIDI_Beat             = Track->context[ _MIDI_Context ].beat;
        _MIDI_Measure          = Track->context[ _MIDI_Context ].measure;
        _MIDI_BeatsPerMeasure  = Track->context[ _MIDI_Context ].BeatsPerMeasure;
        _MIDI_TicksPerBeat     = Track->context[ _MIDI_Context ].TicksPerBeat;
        _MIDI_TimeBase         = Track->context[ _MIDI_Context ].TimeBase;
        TimeSet = TRUE;
        break;

    case EMIDI_LOOP_START :
    case EMIDI_SONG_LOOP_START :
        loopcount = c2 ? c2 : EMIDI_INFINITE;

        if (c1 == EMIDI_SONG_LOOP_START)
        {
            trackptr = _MIDI_TrackPtr;
            tracknum = _MIDI_NumTracks;
        }
        else
        {
            trackptr = Track;
            tracknum = 1;
        }

        while (tracknum > 0)
        {
            trackptr->context[ 0 ].loopcount        = loopcount;
            trackptr->context[ 0 ].pos              = trackptr->pos;
            trackptr->context[ 0 ].loopstart        = trackptr->pos;
            trackptr->context[ 0 ].RunningStatus    = trackptr->RunningStatus;
            trackptr->context[ 0 ].active           = trackptr->active;
            trackptr->context[ 0 ].delay            = trackptr->delay;
            trackptr->context[ 0 ].time             = _MIDI_Time;
            trackptr->context[ 0 ].FPSecondsPerTick = _MIDI_FPSecondsPerTick;
            trackptr->context[ 0 ].tick             = _MIDI_Tick;
            trackptr->context[ 0 ].beat             = _MIDI_Beat;
            trackptr->context[ 0 ].measure          = _MIDI_Measure;
            trackptr->context[ 0 ].BeatsPerMeasure  = _MIDI_BeatsPerMeasure;
            trackptr->context[ 0 ].TicksPerBeat     = _MIDI_TicksPerBeat;
            trackptr->context[ 0 ].TimeBase         = _MIDI_TimeBase;
            trackptr++;
            tracknum--;
        }
        break;

    case EMIDI_LOOP_END :
    case EMIDI_SONG_LOOP_END :
        if ((c2 != EMIDI_END_LOOP_VALUE) || (Track->context[0].loopstart == NULL) || (Track->context[0].loopcount == 0))
            break;

        if (c1 == EMIDI_SONG_LOOP_END)
        {
            trackptr = _MIDI_TrackPtr;
            tracknum = _MIDI_NumTracks;
            _MIDI_ActiveTracks = 0;
        }
        else
        {
            trackptr = Track;
            tracknum = 1;
            _MIDI_ActiveTracks--;
        }

        while (tracknum > 0)
        {
            if (trackptr->context[ 0 ].loopcount != EMIDI_INFINITE)
                trackptr->context[ 0 ].loopcount--;

            trackptr->pos           = trackptr->context[ 0 ].loopstart;
            trackptr->RunningStatus = trackptr->context[ 0 ].RunningStatus;
            trackptr->delay         = trackptr->context[ 0 ].delay;
            trackptr->active        = trackptr->context[ 0 ].active;

            if (trackptr->active)
                _MIDI_ActiveTracks++;

            if (!TimeSet)
            {
                _MIDI_Time             = trackptr->context[ 0 ].time;
                _MIDI_FPSecondsPerTick = trackptr->context[ 0 ].FPSecondsPerTick;
                _MIDI_Tick             = trackptr->context[ 0 ].tick;
                _MIDI_Beat             = trackptr->context[ 0 ].beat;
                _MIDI_Measure          = trackptr->context[ 0 ].measure;
                _MIDI_BeatsPerMeasure  = trackptr->context[ 0 ].BeatsPerMeasure;
                _MIDI_TicksPerBeat     = trackptr->context[ 0 ].TicksPerBeat;
                _MIDI_TimeBase         = trackptr->context[ 0 ].TimeBase;
                TimeSet = TRUE;
            }

            trackptr++;
            tracknum--;
        }
        break;

    default :
        if (_MIDI_Funcs->ControlChange)
            _MIDI_Funcs->ControlChange(channel, c1, c2);
    }

    return TimeSet;
}


/*---------------------------------------------------------------------
   Function: _MIDI_ServiceRoutine

   Task that interperates the MIDI data.
---------------------------------------------------------------------*/

static int32_t _MIDI_ServiceRoutine(void)
{
    if (_MIDI_SongActive)
    {
        int32_t TimeSet = FALSE;
        track   *Track = _MIDI_TrackPtr;
        int32_t tracknum = 0;

        while (tracknum < _MIDI_NumTracks)
        {
            while ((Track->active) && (Track->delay == 0))
            {
                int32_t event;

                GET_NEXT_EVENT(Track, event);

                if (GET_MIDI_COMMAND(event) == MIDI_SPECIAL)
                {
                    switch (event)
                    {
                    case MIDI_SYSEX :
                    case MIDI_SYSEX_CONTINUE :
                        _MIDI_SysEx(Track);
                        break;

                    case MIDI_META_EVENT :
                        _MIDI_MetaEvent(Track);
                        break;
                    }

                    if (Track->active)
                        Track->delay = _MIDI_ReadDelta(Track);

                    continue;
                }

                if (event & MIDI_RUNNING_STATUS)
                {
                    Track->RunningStatus = event;
                }
                else
                {
                    event = Track->RunningStatus;
                    Track->pos--;
                }

                int32_t channel = GET_MIDI_CHANNEL(event);
                int32_t command = GET_MIDI_COMMAND(event);

                int32_t c1 = 0;
                int32_t c2 = 0;

                if (_MIDI_CommandLengths[ command ] > 0)
                {
                    GET_NEXT_EVENT(Track, c1);

                    if (_MIDI_CommandLengths[ command ] > 1)
                        GET_NEXT_EVENT(Track, c2);
                }

                switch (command)
                {
                case MIDI_NOTE_OFF :
                    if (_MIDI_Funcs->NoteOff)
                        _MIDI_Funcs->NoteOff(channel, c1, c2);
                    break;

                case MIDI_NOTE_ON :
                    if (_MIDI_Funcs->NoteOn)
                        _MIDI_Funcs->NoteOn(channel, c1, c2);
                    break;

                case MIDI_POLY_AFTER_TCH :
                    if (_MIDI_Funcs->PolyAftertouch)
                        _MIDI_Funcs->PolyAftertouch(channel, c1, c2);
                    break;

                case MIDI_CONTROL_CHANGE :
                    TimeSet = _MIDI_InterpretControllerInfo(Track, TimeSet, channel, c1, c2);
                    break;

                case MIDI_PROGRAM_CHANGE :
                    if ((_MIDI_Funcs->ProgramChange) && (!Track->EMIDI_ProgramChange))
                        _MIDI_Funcs->ProgramChange(channel, MIDI_PatchMap[ c1 & 0x7f ]);
                    break;

                case MIDI_AFTER_TOUCH :
                    if (_MIDI_Funcs->ChannelAftertouch)
                        _MIDI_Funcs->ChannelAftertouch(channel, c1);
                    break;

                case MIDI_PITCH_BEND :
                    if (_MIDI_Funcs->PitchBend)
                        _MIDI_Funcs->PitchBend(channel, c1, c2);
                    break;

                default :
                    break;
                }

                Track->delay = _MIDI_ReadDelta(Track);
            }

            Track->delay--;
            Track++;
            tracknum++;

            if (_MIDI_ActiveTracks == 0)
            {
                _MIDI_ResetTracks();
                if (_MIDI_Loop)
                {
                    tracknum = 0;
                    Track = _MIDI_TrackPtr;
                }
                else
                {
                    _MIDI_SongActive = FALSE;
                    break;
                }
            }
        }

        _MIDI_AdvanceTick();
        _MIDI_GlobalPositionInTicks++;
    }
    return 0;
}

static int32_t _MIDI_SendControlChange(int32_t channel, int32_t c1, int32_t c2)
{
    if (_MIDI_Funcs == NULL || _MIDI_Funcs->ControlChange == NULL)
        return MIDI_Error;

    _MIDI_Funcs->ControlChange(channel, c1, c2);

    return MIDI_Ok;
}

int32_t MIDI_AllNotesOff(void)
{
    for (int32_t channel = 0; channel < NUM_MIDI_CHANNELS; channel++)
    {
        _MIDI_SendControlChange(channel, 0x40, 0);
        _MIDI_SendControlChange(channel, MIDI_ALL_NOTES_OFF, 0);
        _MIDI_SendControlChange(channel, 0x78, 0);
    }

    return MIDI_Ok;
}

static void _MIDI_SetChannelVolume(int32_t channel, int32_t volume)
{
    _MIDI_ChannelVolume[ channel ] = volume;

    if (_MIDI_Funcs == NULL || _MIDI_Funcs->ControlChange == NULL)
        return;

    _MIDI_Funcs->ControlChange(channel, MIDI_VOLUME, volume);
}

static void _MIDI_SendChannelVolumes(void)
{
    for (int32_t channel = 0; channel < NUM_MIDI_CHANNELS; channel++)
        _MIDI_SetChannelVolume(channel, _MIDI_ChannelVolume[ channel ]);
}

int32_t MIDI_Reset(void)
{
    MIDI_AllNotesOff();

    for (int32_t channel = 0; channel < NUM_MIDI_CHANNELS; channel++)
    {
        _MIDI_SendControlChange(channel, MIDI_RESET_ALL_CONTROLLERS, 0);
        _MIDI_SendControlChange(channel, MIDI_RPN_MSB, MIDI_PITCHBEND_MSB);
        _MIDI_SendControlChange(channel, MIDI_RPN_LSB, MIDI_PITCHBEND_LSB);
        _MIDI_SendControlChange(channel, MIDI_DATAENTRY_MSB, 2); /* Pitch Bend Sensitivity MSB */
        _MIDI_SendControlChange(channel, MIDI_DATAENTRY_LSB, 0); /* Pitch Bend Sensitivity LSB */
        _MIDI_ChannelVolume[ channel ] = GENMIDI_DefaultVolume;
    }

    _MIDI_SendChannelVolumes();

    Reset = TRUE;

    return MIDI_Ok;
}


/*---------------------------------------------------------------------
   Function: MIDI_SetVolume

   Sets the total volume of the music.
---------------------------------------------------------------------*/

int32_t MIDI_SetVolume(int32_t volume)
{
    if (_MIDI_Funcs == NULL)
        return MIDI_NullMidiModule;

    volume = clamp(volume, 0, MIDI_MaxVolume);

    _MIDI_TotalVolume = volume;

    _MIDI_SendChannelVolumes();

    return MIDI_Ok;
}

void MIDI_ContinueSong(void)
{
    if (_MIDI_SongLoaded)
    {
        _MIDI_SongActive = TRUE;
        MPU_Unpause();
    }
}

void MIDI_PauseSong(void)
{
    if (_MIDI_SongLoaded)
    {
        _MIDI_SongActive = FALSE;
        MIDI_AllNotesOff();
        MPU_Pause();
    }
}

/*---------------------------------------------------------------------
   Function: MIDI_SetMidiFuncs

   Selects the routines that send the MIDI data to the music device.
---------------------------------------------------------------------*/

void MIDI_SetMidiFuncs(midifuncs *funcs) { _MIDI_Funcs = funcs; }

void MIDI_StopSong(void)
{
    if (_MIDI_SongLoaded)
    {
        _MIDI_SongActive = FALSE;
        _MIDI_SongLoaded = FALSE;

        MIDI_Reset();
        _MIDI_ResetTracks();

        DO_FREE_AND_NULL(_MIDI_TrackPtr);

        _MIDI_NumTracks    = 0;
        _MIDI_TrackMemSize = 0;

        _MIDI_TotalTime     = 0;
        _MIDI_TotalTicks    = 0;
        _MIDI_TotalBeats    = 0;
        _MIDI_TotalMeasures = 0;

        MPU_Reset();
    }
}

int32_t MIDI_PlaySong(char *song, int32_t loopflag)
{
    if (_MIDI_SongLoaded)
        MIDI_StopSong();

    MPU_Init(MUSIC_SoundDevice);

    _MIDI_Loop = loopflag;

    if (_MIDI_Funcs == NULL)
        return MIDI_NullMidiModule;

    if (B_UNBUF32(song) != MIDI_HEADER_SIGNATURE)
        return MIDI_InvalidMidiFile;

    song += sizeof(int32_t);

    int headersize      = _MIDI_ReadNumber(song, sizeof(int32_t));
    song += sizeof(int32_t);
    int format          = _MIDI_ReadNumber(song, sizeof(int16_t));
    _MIDI_NumTracks = _MIDI_ReadNumber(song + sizeof(int16_t), sizeof(int16_t));
    _MIDI_Division  = _MIDI_ReadNumber(song + sizeof(int16_t) + sizeof(int16_t), sizeof(int16_t));

    // If a SMPTE time division is given, just set to 96 so no errors occur
    if (_MIDI_Division < 0)
        _MIDI_Division = 96;

    if (format > MAX_FORMAT)
        return MIDI_UnknownMidiFormat;

    char *ptr = song + headersize;

    if (_MIDI_NumTracks == 0)
        return MIDI_NoTracks;

    _MIDI_TrackMemSize = _MIDI_NumTracks  * sizeof(track);
    _MIDI_TrackPtr = (track *)Xmalloc(_MIDI_TrackMemSize);

    track *CurrentTrack = _MIDI_TrackPtr;
    int numtracks    = _MIDI_NumTracks-1;

    do
    {
        if (B_UNBUF32(ptr) != MIDI_TRACK_SIGNATURE)
        {
            DO_FREE_AND_NULL(_MIDI_TrackPtr);
            _MIDI_TrackMemSize = 0;

            return MIDI_InvalidTrack;
        }

        int tracklength = _MIDI_ReadNumber(ptr + sizeof(int32_t), sizeof(int32_t));
        ptr += sizeof(int32_t) + sizeof(int32_t);
        CurrentTrack->start = ptr;
        ptr += tracklength;
        CurrentTrack++;
    }
    while (numtracks--);

    _MIDI_InitEMIDI();
    _MIDI_ResetTracks();

    if (!Reset)
        MIDI_Reset();

    Reset = FALSE;

    MIDI_SetDivision(_MIDI_Division);

    _MIDI_SongLoaded = TRUE;
    _MIDI_SongActive = TRUE;

    while (_MPU_BuffersWaiting < 4) _MIDI_ServiceRoutine();

    MPU_BeginPlayback();

    return MIDI_Ok;
}

void MIDI_SetTempo(int32_t tempo)
{
    MIDI_Tempo = tempo;
    _MIDI_FPSecondsPerTick = tabledivide32_noinline(1 << TIME_PRECISION, ((tempo * _MIDI_Division) / 60));
    MPU_SetTempo(tempo);
}

void MIDI_SetDivision(int32_t division)
{
    MPU_SetDivision(division);
}

static void _MIDI_InitEMIDI(void)
{
    int32_t const type = EMIDI_GeneralMIDI;

    _MIDI_ResetTracks();

    _MIDI_TotalTime     = 0;
    _MIDI_TotalTicks    = 0;
    _MIDI_TotalBeats    = 0;
    _MIDI_TotalMeasures = 0;

    track *Track = _MIDI_TrackPtr;
    int32_t tracknum = 0;
    while ((tracknum < _MIDI_NumTracks) && (Track != NULL))
    {
        _MIDI_Tick = 0;
        _MIDI_Beat = 1;
        _MIDI_Measure = 1;
        _MIDI_Time = 0;
        _MIDI_BeatsPerMeasure = 4;
        _MIDI_TicksPerBeat = _MIDI_Division;
        _MIDI_TimeBase = 4;

        _MIDI_PositionInTicks = 0;
        _MIDI_ActiveTracks    = 0;
        _MIDI_Context         = -1;

        Track->RunningStatus = 0;
        Track->active        = TRUE;

        Track->EMIDI_ProgramChange = FALSE;
        Track->EMIDI_VolumeChange  = FALSE;
        Track->EMIDI_IncludeTrack  = TRUE;

        memset(Track->context, 0, sizeof(Track->context));

        while (Track->delay > 0)
        {
            _MIDI_AdvanceTick();
            Track->delay--;
        }

        int IncludeFound = FALSE;
        while (Track->active)
        {
            int32_t event;

            GET_NEXT_EVENT(Track, event);

            if (GET_MIDI_COMMAND(event) == MIDI_SPECIAL)
            {
                switch (event)
                {
                case MIDI_SYSEX :
                case MIDI_SYSEX_CONTINUE :
                    _MIDI_SysEx(Track);
                    break;

                case MIDI_META_EVENT :
                    _MIDI_MetaEvent(Track);
                    break;
                }

                if (Track->active)
                {
                    Track->delay = _MIDI_ReadDelta(Track);
                    while (Track->delay > 0)
                    {
                        _MIDI_AdvanceTick();
                        Track->delay--;
                    }
                }

                continue;
            }

            if (event & MIDI_RUNNING_STATUS)
                Track->RunningStatus = event;
            else
            {
                event = Track->RunningStatus;
                Track->pos--;
            }

            int32_t const command = GET_MIDI_COMMAND(event);
            int32_t length = _MIDI_CommandLengths[ command ];

            if (command == MIDI_CONTROL_CHANGE)
            {
                if (*Track->pos == MIDI_MONO_MODE_ON)
                    length++;

                int32_t    c1, c2;

                GET_NEXT_EVENT(Track, c1);
                GET_NEXT_EVENT(Track, c2);

                length -= 2;

                switch (c1)
                {
                case EMIDI_LOOP_START :
                case EMIDI_SONG_LOOP_START :
                    Track->context[ 0 ].loopcount        = c2 ? c2 : EMIDI_INFINITE;
                    Track->context[ 0 ].pos              = Track->pos;
                    Track->context[ 0 ].loopstart        = Track->pos;
                    Track->context[ 0 ].RunningStatus    = Track->RunningStatus;
                    Track->context[ 0 ].time             = _MIDI_Time;
                    Track->context[ 0 ].FPSecondsPerTick = _MIDI_FPSecondsPerTick;
                    Track->context[ 0 ].tick             = _MIDI_Tick;
                    Track->context[ 0 ].beat             = _MIDI_Beat;
                    Track->context[ 0 ].measure          = _MIDI_Measure;
                    Track->context[ 0 ].BeatsPerMeasure  = _MIDI_BeatsPerMeasure;
                    Track->context[ 0 ].TicksPerBeat     = _MIDI_TicksPerBeat;
                    Track->context[ 0 ].TimeBase         = _MIDI_TimeBase;
                    break;

                case EMIDI_LOOP_END :
                case EMIDI_SONG_LOOP_END :
                    if (c2 == EMIDI_END_LOOP_VALUE)
                    {
                        Track->context[ 0 ].loopstart = NULL;
                        Track->context[ 0 ].loopcount = 0;
                    }
                    break;

                case EMIDI_INCLUDE_TRACK :
                    if (EMIDI_AffectsCurrentCard(c2, type))
                    {
                        //printf( "Include track %d on card %d\n", tracknum, c2 );
                        IncludeFound = TRUE;
                        Track->EMIDI_IncludeTrack = TRUE;
                    }
                    else if (!IncludeFound)
                    {
                        //printf( "Track excluded %d on card %d\n", tracknum, c2 );
                        IncludeFound = TRUE;
                        Track->EMIDI_IncludeTrack = FALSE;
                    }
                    break;

                case EMIDI_EXCLUDE_TRACK :
                    if (EMIDI_AffectsCurrentCard(c2, type))
                    {
                        //printf( "Exclude track %d on card %d\n", tracknum, c2 );
                        Track->EMIDI_IncludeTrack = FALSE;
                    }
                    break;

                case EMIDI_PROGRAM_CHANGE :
                    if (!Track->EMIDI_ProgramChange)
                        //printf( "Program change on track %d\n", tracknum );
                        Track->EMIDI_ProgramChange = TRUE;
                    break;

                case EMIDI_VOLUME_CHANGE :
                    if (!Track->EMIDI_VolumeChange)
                        //printf( "Volume change on track %d\n", tracknum );
                        Track->EMIDI_VolumeChange = TRUE;
                    break;

                case EMIDI_CONTEXT_START :
                    if ((c2 > 0) && (c2 < EMIDI_NUM_CONTEXTS))
                    {
                        Track->context[ c2 ].pos              = Track->pos;
                        Track->context[ c2 ].loopstart        = Track->context[ 0 ].loopstart;
                        Track->context[ c2 ].loopcount        = Track->context[ 0 ].loopcount;
                        Track->context[ c2 ].RunningStatus    = Track->RunningStatus;
                        Track->context[ c2 ].time             = _MIDI_Time;
                        Track->context[ c2 ].FPSecondsPerTick = _MIDI_FPSecondsPerTick;
                        Track->context[ c2 ].tick             = _MIDI_Tick;
                        Track->context[ c2 ].beat             = _MIDI_Beat;
                        Track->context[ c2 ].measure          = _MIDI_Measure;
                        Track->context[ c2 ].BeatsPerMeasure  = _MIDI_BeatsPerMeasure;
                        Track->context[ c2 ].TicksPerBeat     = _MIDI_TicksPerBeat;
                        Track->context[ c2 ].TimeBase         = _MIDI_TimeBase;
                    }
                    break;

                case EMIDI_CONTEXT_END :
                    break;
                }
            }

            Track->pos += length;
            Track->delay = _MIDI_ReadDelta(Track);

            while (Track->delay > 0)
            {
                _MIDI_AdvanceTick();
                Track->delay--;
            }
        }

        _MIDI_TotalTime = max(_MIDI_TotalTime, _MIDI_Time);

        if (RELATIVE_BEAT(_MIDI_Measure, _MIDI_Beat, _MIDI_Tick) >
            RELATIVE_BEAT(_MIDI_TotalMeasures, _MIDI_TotalBeats, _MIDI_TotalTicks))
        {
            _MIDI_TotalTicks    = _MIDI_Tick;
            _MIDI_TotalBeats    = _MIDI_Beat;
            _MIDI_TotalMeasures = _MIDI_Measure;
        }

        Track++;
        tracknum++;
    }

    _MIDI_ResetTracks();
}


void MIDI_UpdateMusic(void)
{
    if (!_MIDI_SongLoaded || !_MIDI_SongActive) return;
    while (_MPU_BuffersWaiting < 4) _MIDI_ServiceRoutine();
}