scummvm/engines/agos/midiparser_simonwin.cpp

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 3 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "common/debug.h"
#include "agos/midiparser_simonwin.h"

#include "audio/mididrv.h"

namespace AGOS {

MidiParser_SimonWin::MidiParser_SimonWin(int8 source, bool useDosTempos) :
	MidiParser_SMF(source), _useDosTempos(useDosTempos) { }

void MidiParser_SimonWin::parseNextEvent(EventInfo &info) {
	byte *parsePos = _position._subtracks[info.subtrack]._playPos;
	uint8 *start = parsePos;
	uint32 delta = readVLQ(parsePos);
	uint8 event = *(parsePos++);

	// Pitch bend events in the Simon 1 data are broken. They contain just the
	// command byte; no data bytes follow. We generate an empty event and set
	// the noop flag to have MidiParser process only the delta and otherwise
	// ignore the event.
	if ((event & 0xF0) == MidiDriver::MIDI_COMMAND_PITCH_BEND) {
		info.start = start;
		info.delta = delta;
		info.event = event;
		info.basic.param1 = 0;
		info.basic.param2 = 0;
		info.length = 0;
		info.noop = true;

		_position._subtracks[info.subtrack]._playPos = parsePos;
	} else {
		// Processing of the other events is the same as the SMF format.
		info.noop = false;
		MidiParser_SMF::parseNextEvent(info);
	}
}

void MidiParser_SimonWin::setTempo(uint32 tempo) {
	uint32 newTempo = tempo;
	if (_useDosTempos && tempo < 750000) {
		// WORKAROUND The tempos set in the SMF data of Simon 1 Windows are
		// faster than the DOS version for the faster tempos. These are
		// corrected here to match the DOS version. The correct tempos have
		// been determined by measuring the tempos generated by the DOS version
		// running in DOSBox.
		newTempo = 330000 + (((tempo / 125000) - 2) * 105000);
	}
	MidiParser::setTempo(newTempo);
}

int32 MidiParser_SimonWin::determineDataSize(Common::SeekableReadStream *stream) {
	int64 startPos = stream->pos();

	// Read the number of tracks.
	byte numSongs = stream->readByte();
	if (numSongs > MAXIMUM_TRACKS) {
		warning("MidiParser_SimonWin::determineDataSize - Can only handle %d tracks but was handed %d", MAXIMUM_TRACKS, numSongs);
		return -1;
	}

	// Add up the sizes of the individual SMF tracks.
	int32 totalSize = 1;
	for (int i = 0; i < numSongs; ++i) {
		int size = MidiParser_SMF::determineDataSize(stream);
		if (size < 0)
			return -1;

		totalSize += size;
		stream->seek(startPos + totalSize, SEEK_SET);
	}

	return totalSize;
}

bool MidiParser_SimonWin::loadMusic(byte *data, uint32 size) {
	assert(size > 7);

	unloadMusic();

	// The first byte indicates the number of tracks in the MIDI data.
	byte *pos = data;
	_numTracks = *(pos++);
	if (_numTracks > MAXIMUM_TRACKS) {
		warning("MidiParser_SimonWin::loadMusic - Can only handle %d tracks but was handed %d", MAXIMUM_TRACKS, _numTracks);
		return false;
	}

	debug(2, "MidiParser_SimonWin::loadMusic: %d tracks", _numTracks);

	// Read the tracks.
	for (int i = 0; i < _numTracks; ++i) {
		// Read the track header.

		// Make sure there's a MThd.
		if (memcmp(pos, "MThd", 4) != 0) {
			warning("MidiParser_SimonWin::loadMusic - Expected MThd but found '%c%c%c%c' instead", pos[0], pos[1], pos[2], pos[3]);
			return false;
		}
		pos += 4;

		// Verify correct header length.
		uint32 len = read4high(pos);
		if (len != 6) {
			warning("MidiParser_SimonWin::loadMusic - MThd length 6 expected but found %d", len);
			return false;
		}

		// Verify that this MIDI is type 0 or 1 (it is expected to be type 1).
		uint16 numSubtracks = pos[2] << 8 | pos[3];
		assert(numSubtracks >= 1 && numSubtracks <= MAXIMUM_SUBTRACKS);
		uint8 subtrackMidiType = pos[1];
		if (subtrackMidiType >= 2) {
			warning("MidiParser_SimonWin::loadMusic - MIDI track contained a type %d subtrack", subtrackMidiType);
			return false;
		}

		_numSubtracks[i] = numSubtracks;

		// Each track could potentially have a different PPQN, but for Simon 1
		// and 2 all tracks have PPQN 192, so this is not a problem.
		_ppqn = pos[4] << 8 | pos[5];
		pos += len;

		// Now determine all the MTrk (sub)track start offsets.
		for (int j = 0; j < numSubtracks; j++) {
			if (memcmp(pos, "MTrk", 4) != 0) {
				warning("MidiParser_SimonWin::loadMusic - Could not find subtrack header at expected location");
				return false;
			}
			pos += 4;
			uint32 subtrackLength = READ_BE_UINT32(pos);
			pos += 4;

			// Note that we assume the original data passed in
			// will persist beyond this call, i.e. we do NOT
			// copy the data to our own buffer. Take warning....
			_tracks[i][j] = pos;
			pos += subtrackLength;
		}
	}

	_disableAutoStartPlayback = true;
	resetTracking();
	setTempo(500000);
	setTrack(0);
	return true;
}

} // End of namespace AGOS