a_musmid.c

//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
// Copyright(C) 2006 Ben Ryves 2006
// Copyright(C) 2023 Frenkel Smeijers
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// 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.
//
// mus2mid.c - Ben Ryves 2006 - http://benryves.com - benryves@benryves.com
// Use to convert a MUS file into a single track, type 0 MIDI file.

#include "id_heads.h"

#define NUM_CHANNELS 16

#define MIDI_PERCUSSION_CHAN 9
#define MUS_PERCUSSION_CHAN 15

// MUS event codes
typedef enum
{
    mus_releasekey = 0x00,
    mus_presskey = 0x10,
    mus_pitchwheel = 0x20,
    mus_systemevent = 0x30,
    mus_changecontroller = 0x40,
    mus_scoreend = 0x60
} musevent;

// MIDI event codes
typedef enum
{
    midi_releasekey = 0x80,
    midi_presskey = 0x90,
    midi_changecontroller = 0xB0,
    midi_changepatch = 0xC0,
    midi_pitchwheel = 0xE0
} midievent;

// Structure to hold MUS file header
typedef struct
{
    byte id[4];
    uint16_t scorelength;
    uint16_t scorestart;
    uint16_t primarychannels;
    uint16_t secondarychannels;
    uint16_t instrumentcount;
} musheader;

// Standard MIDI type 0 header + track header
static byte midiheader[] =
{
    'M', 'T', 'h', 'd',     // Main header
    0x00, 0x00, 0x00, 0x06, // Header size
    0x00, 0x00,             // MIDI type (0)
    0x00, 0x01,             // Number of tracks
    0x00, 0x46,             // Resolution
    'M', 'T', 'r', 'k',        // Start of track
    0x00, 0x00, 0x00, 0x00  // Placeholder for track length
};

// Cached channel velocities
static byte channelvelocities[] =
{
    127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127
};

// Timestamps between sequences of MUS events

static uint32_t queuedtime = 0;

// Counter for the length of the track

static uint32_t tracksize;

static const byte controller_map[] =
{
    0x00, 0x20, 0x01, 0x07, 0x0A, 0x0B, 0x5B, 0x5D,
    0x40, 0x43, 0x78, 0x7B, 0x7E, 0x7F, 0x79
};

static int32_t channel_map[NUM_CHANNELS];

// Write timestamp to a MIDI file.

static boolean WriteTime(uint32_t time, FILE *midioutput)
{
    uint32_t buffer = time & 0x7F;
    byte writeval;

    while ((time >>= 7) != 0)
    {
        buffer <<= 8;
        buffer |= ((time & 0x7F) | 0x80);
    }

    for (;;)
    {
        writeval = (byte)(buffer & 0xFF);

        if (fwrite(&writeval, 1, 1, midioutput) != 1)
        {
            return true;
        }

        ++tracksize;

        if ((buffer & 0x80) != 0)
        {
            buffer >>= 8;
        }
        else
        {
            queuedtime = 0;
            return false;
        }
    }
}


// Write the end of track marker
static boolean WriteEndTrack(FILE *midioutput)
{
    byte endtrack[] = {0xFF, 0x2F, 0x00};

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(endtrack, 1, 3, midioutput) != 3)
    {
        return true;
    }

    tracksize += 3;
    return false;
}

// Write a key press event
static boolean WritePressKey(byte channel, byte key,
                          byte velocity, FILE *midioutput)
{
    byte working = midi_presskey | channel;

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = key & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = velocity & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    tracksize += 3;

    return false;
}

// Write a key release event
static boolean WriteReleaseKey(byte channel, byte key,
                            FILE *midioutput)
{
    byte working = midi_releasekey | channel;

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = key & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = 0;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    tracksize += 3;

    return false;
}

// Write a pitch wheel/bend event
static boolean WritePitchWheel(byte channel, int16_t wheel,
                            FILE *midioutput)
{
    byte working = midi_pitchwheel | channel;

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = wheel & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = (wheel >> 7) & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    tracksize += 3;
    return false;
}

// Write a patch change event
static boolean WriteChangePatch(byte channel, byte patch,
                             FILE *midioutput)
{
    byte working = midi_changepatch | channel;

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = patch & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    tracksize += 2;

    return false;
}

// Write a valued controller change event

static boolean WriteChangeController_Valued(byte channel,
                                         byte control,
                                         byte value,
                                         FILE *midioutput)
{
    byte working = midi_changecontroller | channel;

    if (WriteTime(queuedtime, midioutput))
    {
        return true;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    working = control & 0x7F;

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    // Quirk in vanilla DOOM? MUS controller values should be
    // 7-bit, not 8-bit.

    working = value;// & 0x7F;

    // Fix on said quirk to stop MIDI players from complaining that
    // the value is out of range:

    if (working & 0x80)
    {
        working = 0x7F;
    }

    if (fwrite(&working, 1, 1, midioutput) != 1)
    {
        return true;
    }

    tracksize += 3;

    return false;
}

// Write a valueless controller change event
static boolean WriteChangeController_Valueless(byte channel,
                                            byte control,
                                            FILE *midioutput)
{
    return WriteChangeController_Valued(channel, control, 0,
                                             midioutput);
}

// Allocate a free MIDI channel.

static int32_t AllocateMIDIChannel(void)
{
    int32_t result;
    int32_t max;
    int32_t i;

    // Find the current highest-allocated channel.

    max = -1;

    for (i=0; i<NUM_CHANNELS; ++i)
    {
        if (channel_map[i] > max)
        {
            max = channel_map[i];
        }
    }

    // max is now equal to the highest-allocated MIDI channel.  We can
    // now allocate the next available channel.  This also works if
    // no channels are currently allocated (max=-1)

    result = max + 1;

    // Don't allocate the MIDI percussion channel!

    if (result == MIDI_PERCUSSION_CHAN)
    {
        ++result;
    }

    return result;
}

// Given a MUS channel number, get the MIDI channel number to use
// in the outputted file.

static int32_t GetMIDIChannel(int32_t mus_channel, FILE *midioutput)
{
    // Find the MIDI channel to use for this MUS channel.
    // MUS channel 15 is the percusssion channel.

    if (mus_channel == MUS_PERCUSSION_CHAN)
    {
        return MIDI_PERCUSSION_CHAN;
    }
    else
    {
        // If a MIDI channel hasn't been allocated for this MUS channel
        // yet, allocate the next free MIDI channel.

        if (channel_map[mus_channel] == -1)
        {
            channel_map[mus_channel] = AllocateMIDIChannel();

            // First time using the channel, send an "all notes off"
            // event. This fixes "The D_DDTBLU disease" described here:
            // https://www.doomworld.com/vb/source-ports/66802-the
            WriteChangeController_Valueless(channel_map[mus_channel], 0x7b,
                                            midioutput);
        }

        return channel_map[mus_channel];
    }
}

static boolean ReadMusHeader(FILE *file, musheader *header)
{
    boolean result;

    result = fread(&header->id, sizeof(byte), 4, file) == 4
          && fread(&header->scorelength, sizeof(short), 1, file) == 1
          && fread(&header->scorestart, sizeof(short), 1, file) == 1
          && fread(&header->primarychannels, sizeof(short), 1, file) == 1
          && fread(&header->secondarychannels, sizeof(short), 1, file) == 1
          && fread(&header->instrumentcount, sizeof(short), 1, file) == 1;

    return result;
}


// Read a MUS file from a stream (musinput) and output a MIDI file to
// a stream (midioutput).
//
// Returns false on success or true on failure.

boolean mus2mid(FILE *musinput, FILE *midioutput, int32_t rate, boolean adlibhack)
{
    // Header for the MUS file
    musheader musfileheader;

    // Descriptor for the current MUS event
    byte eventdescriptor;
    int32_t channel; // Channel number
    musevent event;


    // Bunch of vars read from MUS lump
    byte key;
    byte controllernumber;
    byte controllervalue;

    // Buffer used for MIDI track size record
    byte tracksizebuffer[4];

    // Flag for when the score end marker is hit.
    int32_t hitscoreend = 0;

    // Temp working byte
    byte working;
    // Used in building up time delays
    uint32_t timedelay;

    // Initialise channel map to mark all channels as unused.

    for (channel=0; channel<NUM_CHANNELS; ++channel)
    {
        channel_map[channel] = -1;
    }

    // Grab the header

    if (!ReadMusHeader(musinput, &musfileheader))
    {
        return true;
    }

    // Seek to where the data is held
    if (fseek(musinput, (int32_t)musfileheader.scorestart,
              SEEK_SET) != 0)
    {
        return true;
    }

    // So, we can assume the MUS file is faintly legit. Let's start
    // writing MIDI data...

    midiheader[13] = rate / 2;
    fwrite(midiheader, 1, sizeof(midiheader), midioutput);
    tracksize = 0;

    // Now, process the MUS file:
    while (!hitscoreend)
    {
        // Handle a block of events:

        while (!hitscoreend)
        {
            // Fetch channel number and event code:

            if (fread(&eventdescriptor, 1, 1, musinput) != 1)
            {
                return true;
            }

            channel = GetMIDIChannel(eventdescriptor & 0x0F, midioutput);
            event = eventdescriptor & 0x70;

            switch (event)
            {
                case mus_releasekey:
                    if (fread(&key, 1, 1, musinput) != 1)
                    {
                        return true;
                    }

                    if (WriteReleaseKey(channel, key, midioutput))
                    {
                        return true;
                    }

                    break;

                case mus_presskey:
                    if (fread(&key, 1, 1, musinput) != 1)
                    {
                        return true;
                    }

                    if (key & 0x80)
                    {
                        if (fread(&channelvelocities[channel], 1, 1, musinput) != 1)
                        {
                            return true;
                        }

                        channelvelocities[channel] &= 0x7F;
                    }

                    if (WritePressKey(channel, key,
                                      channelvelocities[channel], midioutput))
                    {
                        return true;
                    }

                    break;

                case mus_pitchwheel:
                    if (fread(&key, 1, 1, musinput) != 1)
                    {
                        break;
                    }
                    if (WritePitchWheel(channel, (int16_t)(key * 64), midioutput))
                    {
                        return true;
                    }

                    break;

                case mus_systemevent:
                    if (fread(&controllernumber, 1, 1, musinput) != 1)
                    {
                        return true;
                    }
                    if (controllernumber < 10 || controllernumber > 14)
                    {
                        return true;
                    }

                    if (controllernumber == 14 && adlibhack)
                    {
                        // All notes off
                        if (WriteChangeController_Valueless(channel,
                                                            0x78,
                                                            midioutput))
                        {
                            return true;
                        }
                        // Reset pitch
                        if (WritePitchWheel(channel, (int16_t)(128 * 64), midioutput))
                        {
                            return true;
                        }
                        // Reset pan
                        if (WriteChangeController_Valued(channel,
                                                         0x0a,
                                                         64,
                                                         midioutput))
                        {
                            return true;
                        }
                        break;
                    }

                    if (WriteChangeController_Valueless(channel,
                                                        controller_map[controllernumber],
                                                        midioutput))
                    {
                        return true;
                    }

                    break;

                case mus_changecontroller:
                    if (fread(&controllernumber, 1, 1, musinput) != 1)
                    {
                        return true;
                    }

                    if (fread(&controllervalue, 1, 1, musinput) != 1)
                    {
                        return true;
                    }

                    if (controllernumber == 0)
                    {
                        if (WriteChangePatch(channel, controllervalue,
                                             midioutput))
                        {
                            return true;
                        }
                    }
                    else
                    {
                        if (controllernumber < 1 || controllernumber > 9)
                        {
                            return true;
                        }

                        if (WriteChangeController_Valued(channel,
                                                         controller_map[controllernumber],
                                                         controllervalue,
                                                         midioutput))
                        {
                            return true;
                        }
                    }

                    break;

                case mus_scoreend:
                    hitscoreend = 1;
                    break;

                default:
                    return true;
                    break;
            }

            if (eventdescriptor & 0x80)
            {
                break;
            }
        }
        // Now we need to read the time code:
        if (!hitscoreend)
        {
            timedelay = 0;
            for (;;)
            {
                if (fread(&working, 1, 1, musinput) != 1)
                {
                    return true;
                }

                timedelay = timedelay * 128 + (working & 0x7F);
                if ((working & 0x80) == 0)
                {
                    break;
                }
            }
            queuedtime += timedelay;
        }
    }

    // End of track
    if (WriteEndTrack(midioutput))
    {
        return true;
    }

    // Write the track size into the stream
    if (fseek(midioutput, 18, SEEK_SET))
    {
        return true;
    }

    tracksizebuffer[0] = (tracksize >> 24) & 0xff;
    tracksizebuffer[1] = (tracksize >> 16) & 0xff;
    tracksizebuffer[2] = (tracksize >> 8) & 0xff;
    tracksizebuffer[3] = tracksize & 0xff;

    if (fwrite(tracksizebuffer, 1, 4, midioutput) != 4)
    {
        return true;
    }

    return false;
}