diff options
| -rw-r--r-- | engines/kyra/sound_adlib.cpp | 26 |
1 files changed, 15 insertions, 11 deletions
diff --git a/engines/kyra/sound_adlib.cpp b/engines/kyra/sound_adlib.cpp index ddea471484..844084bc40 100644 --- a/engines/kyra/sound_adlib.cpp +++ b/engines/kyra/sound_adlib.cpp @@ -248,7 +248,7 @@ private: uint8 _unk5; int _soundsPlaying; - uint16 _unk6; + uint16 _rnd; uint8 _continueFlag; uint8 _unkValue1; @@ -320,7 +320,7 @@ AdlibDriver::AdlibDriver(Audio::Mixer *mixer) { _unkOutputByte2 = _unkOutputByte1 = 0; _lastProcessed = _flagTrigger = _curTable = _unk4 = 0; - _unk6 = 0x1234; + _rnd = 0x1234; _continueFlag = 0; _unkTableByte1 = 0; @@ -611,7 +611,7 @@ void AdlibDriver::callbackProcess() { void AdlibDriver::resetAdlibState() { debugC(9, kDebugLevelSound, "resetAdlibState()"); - _unk6 = 0x1234; + _rnd = 0x1234; // Authorize the control of the waveforms writeOPL(0x01, 0x20); @@ -692,19 +692,23 @@ void AdlibDriver::unkOutput2(uint8 num) { writeOPL(0xB0 + num, 0x20); } -uint16 AdlibDriver::updateUnk6Value() { - _unk6 += 0x9248; - uint16 lowBits = _unk6 & 7; - _unk6 >>= 3; - _unk6 |= lowBits << 13; - return _unk6; +// I believe this is a random number generator. It actually does seem to +// generate an even distribution of almost all numbers from 0 through 65535, +// though in my tests some numbers were never generated. + +uint16 AdlibDriver::getRandomNr() { + _rnd += 0x9248; + uint16 lowBits = _rnd & 7; + _rnd >>= 3; + _rnd |= (lowBits << 13); + return _rnd; } void AdlibDriver::update1(uint8 unk1, OutputState &state) { debugC(9, kDebugLevelSound, "update1(%d, %d)", unk1, &state - _outputTables); _continueFlag = unk1; if (state.unk11) { - state.unk5 = unk1 + (updateUnk6Value() & state.unk11 & 0xFF); + state.unk5 = unk1 + (getRandomNr() & state.unk11 & 0xFF); return; } uint8 value = unk1; @@ -1259,7 +1263,7 @@ int AdlibDriver::updateCallback38(uint8 *&dataptr, OutputState &state, uint8 val int AdlibDriver::updateCallback39(uint8 *&dataptr, OutputState &state, uint8 value) { uint16 unk = *dataptr++; unk |= value << 8; - unk &= updateUnk6Value(); + unk &= getRandomNr(); uint16 unk2 = ((state.unkOutputValue1 & 0x1F) << 8) | state.unk17; unk2 += unk; |