diff options
| -rw-r--r-- | engines/kyra/sound_adlib.cpp | 82 |
1 files changed, 31 insertions, 51 deletions
diff --git a/engines/kyra/sound_adlib.cpp b/engines/kyra/sound_adlib.cpp index 9479742638..9acec28ebf 100644 --- a/engines/kyra/sound_adlib.cpp +++ b/engines/kyra/sound_adlib.cpp @@ -108,9 +108,8 @@ private: // // unk3 - Unknown. Used for turning off some notes. // unk4 - Unknown. Related to sound timing? - // unk5 - Unknown. Used for turning off some notes. // unk7 - Unknown. Used for turning off some notes. - // unk11 - Unknown. Used for updating unk5. + // unk11 - Unknown. Used for updating random durations. // unk12 - Unknown. Used for updating unk7. // unk16 - Sound-related. Possibly some sort of pitch bend. // unk18 - Sound-effect. Used for secondaryEffect1() @@ -135,7 +134,7 @@ private: struct OutputState { uint8 opExtraLevel2; uint8 *dataptr; - uint8 unk5; + uint8 duration; uint8 repeatCounter; int8 baseOctave; uint8 priority; @@ -157,7 +156,7 @@ private: uint8 unk7; uint8 baseFreq; int8 tempo; - int8 unk4; + int8 position; uint8 regAx; uint8 regBx; typedef void (AdlibDriver::*Callback)(OutputState&); @@ -617,8 +616,8 @@ void AdlibDriver::callbackOutput() { table.priority = priority; table.dataptr = ptr; table.tempo = -1; - table.unk4 = -1; - table.unk5 = 1; + table.position = -1; + table.duration = 1; if (index != 9) { unkOutput2(index); } @@ -631,23 +630,24 @@ void AdlibDriver::callbackOutput() { // A few words on opcode parsing and timing: // -// We have a timer callback that is called every 13888 us. +// First of all, We simulate a timer callback 72 times per second. Each timeout +// we update each channel that has something to play. // -// Each channel appears to have its own individual tempo, unk1, which is added -// to unk4. If this causes unk4 to wrap around to negative, something happens. +// Each channel has its own individual tempo, which is added to its position. +// This will frequently cause the position to "wrap around" but that is +// intentional. In fact, it's the signal to go ahead and do more stuff with +// that channel. // -// When "something happens", unk5 is decreased. If unk5 is still non-zero, -// nothing much happens. Notes may be turned off depending on unk3 and unk7, -// but other than that no new commands are issued. -// -// If unk5 reaches zero, a new set of music opcodes are executed. In effect, -// unk5 is the duration of the channel's most recent opcode. Either a note or -// a pause, presumably. +// Each channel also has a duration, indicating how much time is left on the +// its current task. This duration is decreased by one. As long as it still has +// not reached zero, the only thing that can happen is that depending on unk3 +// and unk7 the current note may be stopped. Once the duration reaches zero, a +// new set of musical opcodes are executed. // // An opcode is one byte, followed by a variable number of parameters. Since // most opcodes have at least one one-byte parameter, we read that as well. Any -// opcode that doesn't have that one parameter is responsible for backing the -// data pointer. +// opcode that doesn't have that one parameter is responsible for moving the +// data pointer back again. // // If the most significant bit of the opcode is 1, it's a function; call it. If // it returns something greater than zero, it's the last opcode in the current @@ -663,26 +663,6 @@ void AdlibDriver::callbackOutput() { // Finally, most of the times that the callback is called, it will invoke the // effects callbacks. The final opcode in a set can prevent this, if it's a // function and it returns anything other than 1. -// -// To summarize: -// -// unk1 is the channel tempo, assisted by unk4 -// unk5 is the duration of the last opcode (probably a note) of a set -// unk3 and unk7 can turn off notes prematurely; to implement staccatto? -// -// Some possible sources of tempo bugs: -// -// The timer has a 10 ms resolution. Over time it will be pretty accurate, but -// individual calls may be a bit off. The only notes that are this short are -// the ones played by the effects callbacks, so it shouldn't matter much. -// -// Adding unk1 to a negative unk4 does not necessarily take it out of the -// negative range, so it may trigger twice in a row. Again, this shouldn't -// matter much. -// -// The unk5 variable (duration) may be incorrectly set. -// -// An opcode function may be returning the wrong value. void AdlibDriver::callbackProcess() { for (_curTable = 9; _curTable >= 0; --_curTable) { @@ -697,13 +677,13 @@ void AdlibDriver::callbackProcess() { table.tempo = _tempo; } - int8 backup = table.unk4; - table.unk4 += table.tempo; - if (table.unk4 < backup) { - if (--table.unk5) { - if (table.unk5 == table.unk7) + int8 backup = table.position; + table.position += table.tempo; + if (table.position < backup) { + if (--table.duration) { + if (table.duration == table.unk7) noteOff(table); - if (table.unk5 == table.unk3 && _curTable != 9) + if (table.duration == table.unk3 && _curTable != 9) noteOff(table); } else { int8 opcode = 0; @@ -852,13 +832,13 @@ void AdlibDriver::setupDuration(uint8 duration, OutputState &state) { debugC(9, kDebugLevelSound, "setupDuration(%d, %d)", duration, &state - _outputTables); _continueFlag = duration; if (state.unk11) { - state.unk5 = duration + (getRandomNr() & state.unk11); + state.duration = duration + (getRandomNr() & state.unk11); return; } if (state.unk12) { state.unk7 = (duration >> 3) * state.unk12; } - state.unk5 = duration; + state.duration = duration; } // This function may or may not play the note. It's usually followed by a call @@ -1228,8 +1208,8 @@ int AdlibDriver::updateCallback3(uint8 *&dataptr, OutputState &state, uint8 valu state2.priority = priority; state2.dataptr = ptr; state2.tempo = -1; - state2.unk4 = -1; - state2.unk5 = 1; + state2.position = -1; + state2.duration = 1; unkOutput2(table); } return 0; @@ -1309,7 +1289,7 @@ int AdlibDriver::update_setupSecondaryEffect1(uint8 *&dataptr, OutputState &stat int AdlibDriver::updateCallback15(uint8 *&dataptr, OutputState &state, uint8 value) { OutputState &state2 = _outputTables[value]; - state2.unk5 = 0; + state2.duration = 0; state2.priority = 0; state2.dataptr = 0; return 0; @@ -1391,7 +1371,7 @@ int AdlibDriver::updateCallback24(uint8 *&dataptr, OutputState &state, uint8 val } dataptr -= 2; - state.unk5 = 1; + state.duration = 1; return 2; } @@ -1495,7 +1475,7 @@ int AdlibDriver::updateCallback38(uint8 *&dataptr, OutputState &state, uint8 val _curTable = value; OutputState &state2 = _outputTables[value]; - state2.unk5 = state2.priority = 0; + state2.duration = state2.priority = 0; state2.dataptr = 0; state2.opExtraLevel2 = 0; |