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AGOS: Proper implementation of the Simon 1 demo aka Accolade MIDI par…
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…ser.

This is based on the Elvira 1 demo.
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Johannes Schickel committed Aug 21, 2011
1 parent 7173dbf commit f705a9b
Showing 1 changed file with 97 additions and 110 deletions.
207 changes: 97 additions & 110 deletions engines/agos/midiparser_s1d.cpp
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Expand Up @@ -31,166 +31,151 @@ namespace AGOS {

/**
* Simon 1 Demo version of MidiParser.
*
* This parser is the result of eyeballing the one MUS file that's included
* with simon1demo. So there might be some things missing. I've tried to notate
* question-mark areas where they occur.
*/
class MidiParser_S1D : public MidiParser {
protected:
private:
byte *_data;
bool _no_delta;

struct Loop {
uint16 timer;
byte *start, *end;
} _loops[16];

uint32 readVLQ2(byte *&data);
void chainEvent(EventInfo &info);
protected:
void parseNextEvent(EventInfo &info);
void resetTracking();
uint32 readVLQ2(byte * &data);

public:
MidiParser_S1D() : _data(0), _no_delta(false) {}

bool loadMusic(byte *data, uint32 size);
};

uint32 MidiParser_S1D::readVLQ2(byte *&data) {
uint32 delta = 0;

// The VLQs for simon1demo seem to be
// in Little Endian format.
uint32 MidiParser_S1D::readVLQ2(byte * &data) {
byte str;
uint32 value = 0;
int i;

for (i = 0; i < 4; ++i) {
str = data[0];
++data;
value |= (str & 0x7F) << (i * 7);
if (!(str & 0x80))
break;
// LE format VLQ, which is 2 bytes long at max.
delta = *data++;
if (delta & 0x80) {
delta &= 0x7F;
delta |= *data++ << 7;
}
return value;

return delta;
}

void MidiParser_S1D::chainEvent(EventInfo &info) {
// When we chain an event, we add up the old delta.
uint32 delta = info.delta;
parseNextEvent(info);
info.delta += delta;
}

void MidiParser_S1D::parseNextEvent(EventInfo &info) {
info.start = _position._play_pos;
info.length = 0;
info.delta = _no_delta ? 0 : readVLQ2(_position._play_pos);

_no_delta = false;
info.event = *(_position._play_pos++);
if (info.command() < 0x8) {

info.event = *_position._play_pos++;
if (!(info.event & 0x80)) {
_no_delta = true;
info.event += 0x80;
info.event |= 0x80;
}

switch (info.command()) {
case 0x8:
info.basic.param1 = *(_position._play_pos++);
info.basic.param2 = 0;
info.length = 0;
break;

case 0x9:
info.basic.param1 = *(_position._play_pos++);
info.basic.param2 = *(_position._play_pos++); // I'm ASSUMING this byte is velocity!
info.length = 0;
break;

case 0xA:
case 0xB:
// I'm not sure what these are meant to do, or what the
// parameter is. Elvira 1 needs them, though, and who am I to
// argue with her?
info.basic.param1 = *(_position._play_pos++);
info.basic.param2 = 0;
break;

case 0xC:
info.basic.param1 = *(_position._play_pos++);
info.basic.param2 = 0;
++_position._play_pos; // I have NO IDEA what the second byte is for.
break;

case 0xD:
// Triggered by MOD0/MOD1/MOD2/MOD3/MOD4/MOD6/MOD7/MOD8/MOD9 in Elvira 2
// Triggered by MOD0/MOD2/MOD3/MOD5/MOD6/MOD7/MOD8/MOD9/MOD10/MOD12/MOD14/MOD15/MOD20 in Waxworks
break;

case 0xE:
// Triggered by MOD9 in Elvira 1
// Triggered by MOD3/MOD5 in Elvira 2
// Triggered by MOD3/MOD7/MOD8/MOD13 in Waxworks
break;

case 0xF:
switch (info.event & 0x0F) {
case 0x0:
// Trigged by MOD2/MOD6/MOD15 in Waxworks
// Pure guesswork
info.ext.type = *(_position._play_pos++);
info.length = readVLQ(_position._play_pos);
info.ext.data = _position._play_pos;
break;

case 0x3: // Not sure, Song Select?
// Trigged by MOD1/MOD7/MOD10 in Elvira 1
info.basic.param1 = *(_position._play_pos++);
if (info.event == 0xFC) {
// This means End of Track.
// Rewrite in SMF (MIDI transmission) form.
info.event = 0xFF;
info.ext.type = 0x2F;
} else {
switch (info.command()) {
case 0x8: // note off
info.basic.param1 = *_position._play_pos++;
info.basic.param2 = 0;
break;

case 0x4:
// Trigged by MOD8 in Elvira 1
break;

case 0x7:
// Trigged by MOD6 in Elvira 2
// Trigged by MOD5 in Waxworks
case 0x9: // note on
info.basic.param1 = *_position._play_pos++;
info.basic.param2 = *_position._play_pos++;
break;

case 0x8: // Not sure, ?
// Trigged by MOD19 in Waxworks
info.basic.param1 = info.basic.param2 = 0;
case 0xA: { // loop control
// In case the stop mode(?) is set to 0x80 this will stop the
// track over here.

const int16 loopIterations = int8(*_position._play_pos++);
if (!loopIterations) {
_loops[info.channel()].start = _position._play_pos;
} else {
if (!_loops[info.channel()].timer) {
if (_loops[info.channel()].start) {
_loops[info.channel()].timer = uint16(loopIterations);
_loops[info.channel()].end = _position._play_pos;

// Go to the start of the loop
_position._play_pos = _loops[info.channel()].start;
}
} else {
if (_loops[info.channel()].timer)
_position._play_pos = _loops[info.channel()].start;
--_loops[info.channel()].timer;
}
}

// We need to read the next midi event here. Since we can not
// safely pass this event to the MIDI event processing.
chainEvent(info);
} break;

case 0xB: // auto stop marker(?)
// In case the stop mode(?) is set to 0x80 this will stop the
// track.

// We need to read the next midi event here. Since we can not
// safely pass this event to the MIDI event processing.
chainEvent(info);
break;

case 0xA:
// Trigged by MOD5 in Elvira 2
case 0xC: // program change
info.basic.param1 = *_position._play_pos++;
info.basic.param2 = 0;
break;

case 0xC:
// This means End of Track.
// Rewrite in SMF (MIDI transmission) form.
info.event = 0xFF;
info.ext.type = 0x2F;
info.length = 0;
break;
case 0xD: // jump to loop end
if (_loops[info.channel()].end)
_position._play_pos = _loops[info.channel()].end;

case 0xF: // Not sure, META event?
// Trigged by MOD8/MOD9/MOD11/MOD12/MOD13 in Waxworks
info.ext.type = *(_position._play_pos++);
info.length = readVLQ(_position._play_pos);
info.ext.data = _position._play_pos;
_position._play_pos += info.length;
// We need to read the next midi event here. Since we can not
// safely pass this event to the MIDI event processing.
chainEvent(info);
break;

default:
error("MidiParser_S1D: Unexpected type 0x%02X found", (int) info.event);
// The original called some other function from here, which seems
// not to be MIDI related.
warning("MidiParser_S1D: default case %d", info.channel());

// We need to read the next midi event here. Since we can not
// safely pass this event to the MIDI event processing.
chainEvent(info);
break;
}
break;
default:
error("MidiParser_S1D: Unexpected event 0x%02X found", (int) info.command());
break;
}
}

bool MidiParser_S1D::loadMusic(byte *data, uint32 size) {
unloadMusic();

// The original actually just ignores the first two bytes.
byte *pos = data;
if (*(pos++) != 0xFC)
debug(1, "Expected 0xFC header but found 0x%02X instead", (int) *pos);

// The next 3 bytes MIGHT be tempo, but we skip them and use the default.
// setTempo (*(pos++) | (*(pos++) << 8) | (*(pos++) << 16));
pos += 3;
pos += 1;

// And now we're at the actual data. Only one track.
_num_tracks = 1;
Expand All @@ -208,7 +193,9 @@ bool MidiParser_S1D::loadMusic(byte *data, uint32 size) {

void MidiParser_S1D::resetTracking() {
MidiParser::resetTracking();
_no_delta = false;
// The first event never contains any delta.
_no_delta = true;
memset(_loops, 0, sizeof(_loops));
}

MidiParser *MidiParser_createS1D() { return new MidiParser_S1D; }
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