diff options
| -rw-r--r-- | engines/kyra/sound_adlib.cpp | 61 |
1 files changed, 33 insertions, 28 deletions
diff --git a/engines/kyra/sound_adlib.cpp b/engines/kyra/sound_adlib.cpp index 4fb0c626b6..3e8465dbd0 100644 --- a/engines/kyra/sound_adlib.cpp +++ b/engines/kyra/sound_adlib.cpp @@ -311,7 +311,6 @@ private: // _unkValue18 - Unknown. Rhythm section volume? // _unkValue19 - Unknown. Rhythm section volume? // _unkValue20 - Unknown. Rhythm section volume? - // _unkOutputByte2 - Unknown. Something to do with the BD register. // _unkTable[] - Probably frequences for the 12-tone scale. // _unkTable2[] - Unknown. Currently only used by updateCallback46() // _unkTable2_1[] - One of the tables in _unkTable2[] @@ -326,7 +325,6 @@ private: int _lastProcessed; int8 _flagTrigger; int _curChannel; - uint8 _rhythmSection; uint8 _soundTrigger; int _soundsPlaying; @@ -361,7 +359,9 @@ private: uint8 _soundIdTable[0x10]; Channel _channels[10]; - uint8 _unkOutputByte2; + uint8 _vibratoAndAMDepthBits; + uint8 _rhythmSectionBits; + uint8 _curRegOffset; uint8 _tempo; @@ -393,9 +393,9 @@ AdlibDriver::AdlibDriver(Audio::Mixer *mixer) { memset(_channels, 0, sizeof(_channels)); _soundData = 0; - _unkOutputByte2 = _curRegOffset = 0; + _vibratoAndAMDepthBits = _curRegOffset = 0; - _lastProcessed = _flagTrigger = _curChannel = _rhythmSection = 0; + _lastProcessed = _flagTrigger = _curChannel = _rhythmSectionBits = 0; _rnd = 0x1234; _tempo = 0; @@ -790,7 +790,7 @@ void AdlibDriver::noteOff(Channel &channel) { // When the rhythm section is enabled, channels 6, 7 and 8 are special. - if (_rhythmSection && _curChannel >= 6) + if (_rhythmSectionBits && _curChannel >= 6) return; // This means the "Key On" bit will always be 0 @@ -811,7 +811,7 @@ void AdlibDriver::unkOutput2(uint8 chan) { // I believe this has to do with channels 6, 7, and 8 being special // when Adlib's rhythm section is enabled. - if (_rhythmSection && chan >= 6) + if (_rhythmSectionBits && chan >= 6) return; uint8 offset = _regOffset[chan]; @@ -1457,25 +1457,26 @@ int AdlibDriver::update_changeExtraLevel2(uint8 *&dataptr, Channel &channel, uin return 0; } +// Apart from initialising to zero, these two functions are the only ones that +// modify _vibratoAndAMDepthBits. + int AdlibDriver::update_setAMDepth(uint8 *&dataptr, Channel &channel, uint8 value) { if (value & 1) - _unkOutputByte2 |= 0x80; + _vibratoAndAMDepthBits |= 0x80; else - _unkOutputByte2 &= 0x7F; + _vibratoAndAMDepthBits &= 0x7F; - // The AM Depth bit is set or cleared, the others remain unchanged - writeOPL(0xBD, _unkOutputByte2); + writeOPL(0xBD, _vibratoAndAMDepthBits); return 0; } int AdlibDriver::update_setVibratoDepth(uint8 *&dataptr, Channel &channel, uint8 value) { if (value & 1) - _unkOutputByte2 |= 0x40; + _vibratoAndAMDepthBits |= 0x40; else - _unkOutputByte2 &= 0xBF; + _vibratoAndAMDepthBits &= 0xBF; - // The Vibrato Depth bit is set or cleared, the others remain unchanged - writeOPL(0xBD, _unkOutputByte2); + writeOPL(0xBD, _vibratoAndAMDepthBits); return 0; } @@ -1629,7 +1630,7 @@ int AdlibDriver::update_setupRhythmSection(uint8 *&dataptr, Channel &channel, ui writeOPL(0xB8, _channels[8].regBx); writeOPL(0xA8, *dataptr++); - _rhythmSection = 0x20; + _rhythmSectionBits = 0x20; _curRegOffset = regOffsetBackUp; _curChannel = channelBackUp; @@ -1637,29 +1638,33 @@ int AdlibDriver::update_setupRhythmSection(uint8 *&dataptr, Channel &channel, ui } int AdlibDriver::update_playRhythmSection(uint8 *&dataptr, Channel &channel, uint8 value) { - // Amplitude Modulation Depth / Vibrato Depth / Rhythm - writeOPL(0xBD, (((value & 0x1F) ^ 0xFF) & _rhythmSection) | 0x20); + // Any instrument that we want to play, and which was already playing, + // is temporarily keyed off. Instruments that were off already, or + // which we don't want to play, retain their old on/off status. This is + // probably so that the instrument's envelope is played from its + // beginning again... - value |= _rhythmSection; - _rhythmSection = value; + writeOPL(0xBD, (_rhythmSectionBits & ~(value & 0x1F)) | 0x20); - value |= _unkOutputByte2; - value |= 0x20; + // ...but since we only set the rhythm instrument bits, and never clear + // them (until the entire rhythm section is disabled), I'm not sure how + // useful the cleverness above is. We could perhaps simply turn off all + // the rhythm instruments instead. - // The original only wrote to the data port here, but that shouldn't - // make any real difference. + _rhythmSectionBits |= value; - writeOPL(0xBD, value); + writeOPL(0xBD, _vibratoAndAMDepthBits | 0x20 | _rhythmSectionBits); return 0; } int AdlibDriver::update_removeRhythmSection(uint8 *&dataptr, Channel &channel, uint8 value) { --dataptr; - _rhythmSection = 0; + _rhythmSectionBits = 0; - // Amplitude Modulation Depth / Vibrato Depth / Rhythm - writeOPL(0xBD, _unkOutputByte2 & 0xC0); + // All the rhythm bits are cleared. The AM and Vibrato depth bits + // remain unchanged. + writeOPL(0xBD, _vibratoAndAMDepthBits); return 0; } |