m64 format

Disassembler: https://gist.github.com/simonlindholm/307e73aefed6e1a358931522c291f878
Disassembly of SM64 US sequence 0: https://paste.rs/6za

Legend

  • u8 means a single byte, interpreted as an unsigned integer
  • s8 means a single byte, interpreted as a signed integer
  • u16 means two bytes, interpreted as a big-endian unsigned integer
  • var means an unsigned integer which is either one or two bytes depending on the top bit of the first byte. If the bit is unset, it's the same as u8; if set, it's the same as u16 with that bit ignored.
  • addr means the same as u16, interpreted as as index into the sequence data.
  • X, Y, Z are the arguments passed to the command
  • N is the lower 4 bites of the command, or lower 6 bits for notes

Sequences

hex mnemonic description
0xff end End of script, loop or function
0xfe delay1 Delay for 1 tick
0xfd, var delay Delay for X ticks
0xfc, addr call Call a function
0xfb, addr jump Jump to a point in the sequence script
0xfa, addr beqz Jump if Q == 0, where Q is an s8 used to hold temporary sequence script state
0xf9, addr bltz Jump if Q < 0
0xf8, u8 loop Repeat until loopend for X iterations (256 if X = 0)
0xf7 loopend Loop end marker
0xf5, addr bgez Jump if Q >= 0
0xf2, u8 reservenotes Reserve X notes for exclusive use by this sequence (dropping earlier reservations). A limited number of notes can be played at once (configurable per level, usually 16); if more than that are played, an existing one will be stopped and reused. This command can prevent that from happening across sequences.
0xf1 unreservenotes Drop all earlier reservations made by this sequence.
0xdf, s8 transpose Set transposition in semitones.
0xde, s8 transposerel Change transposition by some delta.
0xdd, u8 settempo Set tempo in BPM.
0xdc, s8 addtempo Change tempo by some delta.
0xdb, u8 setvol Set volume scale (0..255 = none to twice normal).
0xda, s8 changevol Change volume scale by some delta.
0xd7, u16 initchannels Initialize channels (bitmask). This copies mute behavior and note allocation policy.
0xd6, u16 disablechannels Uninitialize channels (bitmask).
0xd5, s8 setmutescale Set volume multiplier for muted mode (0..127).
0xd4 mute Set sequence to muted mode. Depending on what behavior has been set this will do different things; from lowering volume to not running scripts.
0xd3, u8 setmutebhv Set mute behavior (bitmask). Bit 0x20 lowers volume, bit 0x40 does something to layers, and bit 0x80 pauses the sequence script. Default mute behavior is to have all of those bits set.
0xd2, addr setshortnotevelocitytable Set velocity table for short notes (see further down). Target should be an array of bytes in the sequence data of length 16.
0xd1, addr setshortnotedurationtable Set duration table for short notes (see further down). Target should be an array of bytes in the sequence data of length 16.
0xd0, u8 setnoteallocationpolicy Set note allocation policy (bitmask). If bit 0x1 is set, it will try to steal notes back from what was previously played on the same layer. If bit 0x2 is set, notes will be allocated exclusively from the channel's reserved notes, else if 0x4 is set, from the channel's or sequence's reserved notes, else if 0x8 is set, from unreserved notes, otherwise from all sources. Not used by the game.
0xcc, u8 setval Set Q to a constant.
0xc9, u8 bitand Bitand Q by a constant.
0xc8, u8 subtract Subtract a constant from Q.
0x90-0x9f, addr startchannel Start channel N, with a given channel script.
0x80-0x8f getvariation Set Q to the variation bit, which is initially either 0 or 0x80 (i.e. -128, since Q is s8). This bit comes from the sequence load command. For instance, to play the Koopa shell music, the game plays sequence 0x8E, which is the same as sequence 0xE but with the variation bit set.
0x70-0x7f setvariation Set the variation bit to Q.
0x50-0x5f subvariation Subtract the variation bit from Q.
0x00-0x0f testchdisabled Set Q to 1 or 0, depending on whether channel N has been disabled by channel script.

Channels

hex mnemonic description
0xff end End of script, loop or function
0xfe delay1 Delay for 1 tick
0xfd, var delay Delay for X ticks
0xfc, addr call Call a function
0xfb, addr jump Jump to a point in the channel script
0xfa, addr beqz Jump if Q == 0, where Q is an s8 used to hold temporary channel script state
0xf9, addr bltz Jump if Q < 0
0xf8, u8 loop Repeat until loopend for X iterations (256 if X = 0)
0xf7 loopend Loop end marker
0xf6 break Decrease loop/function stack depth by 1. Combine with a jump to break out of a loop.
0xf5, addr bgez Jump if Q >= 0
0xf3 hang Infinite delay.
0xf2, u8 reservenotes Reserve X notes for exclusive use by this channel (dropping earlier reservations).
0xf1 unreservenotes Drop all earlier reservations made by this channel.
0xe4 dyncall If Q != -1, make a function call to position dyntable[Q], where dyntable is a channel-specific u16 array which can set by setdyntable/dynsetdyntable.
0xe3, u8 setvibratodelay Set delay until vibrato starts for each note.
0xe2, u8, u8, u8 setvibratoextentlinear Set vibrato extent for each note as a function that starts at X, goes up linearly to Y over a time span given by Z, then stays there.
0xe1, u8, u8, u8 setvibratoratelinear Like above except for vibrato rate.
0xe0, u8 setvolscale Set scale factor for volume (0..255 = none to twice normal).
0xdf, u8 setvol Set scale factor #2 for volume (0..255 = none to twice normal). The two scale factors are separately controlled by outer audio logic, e.g. when changing between rooms, when playing sound effects, etc. The game almost exclusively uses setvol, so that should probably be preferred, but setvolscale shows up in a few locations in the sound effect sequence.
0xde, u16 freqscale Pitch bend using a raw frequency multiplier X/2^15.
0xdd, u8 setpan Set the pan for this channel (0..128)
0xdc, u8 setpanchanweight The pan for each note will be computed as W * channel pan + (1 - W) * note pan. This sets W (0..128 maps to 0..1). W defaults to 1.0.
0xdb, s8 transpose Set transposition in semitones.
0xda, addr setenvelope Set ADSR envelope. See below for format.
0xd9, u8 setdecayrelease Set ADSR decay/release rate.
0xd8, u8 setvibratoextent Set vibrato extent.
0xd7, u8 setvibratorate Set vibrato rate.
0xd6, u8 setupdatesperframe Seems like it was meant to set the number of updates per frame? But it doesn't actually do anything.
0xd4, u8 setreverb Set amount of reverb (or "dry/wet mix"?).
0xd3, s8 pitchbend Pitch bend by <= 1 octave in either direction (-127..127).
0xd2, u8 setsustain Set ADSR sustain volume.
0xd1, u8 setnoteallocationpolicy Set note allocation policy for channel. See the description for sequence scripts.
0xd0, u8 stereoheadseteffects Enable (1) or disable (0) some pan/volume effects related to stereo/headset. I don't know which ones precisely – pan is still taken into account even with this disabled. With this disabled, stereo/headset gets the same output.
0xcc, u8 setval Set Q to a constant.
0xcb, addr readseq Set Q to sequenceData[X + Q].
0xca, u8 setmutebhv Set mute behavior for this channel.
0xc9, u8 bitand Bitand Q by a constant.
0xc8, u8 subtract Subtract a constant from Q.
0xc7, u8, addr writeseq Overwrite the byte at the given position in the sequence script by (Q + X).
0xc6, u8 setbank Switch bank within instrument bank sets, to the X'th bank, 0-indexed, counting from the end.
0xc5 dynsetdyntable If Q != -1, set dyntable to point to position dyntable[Q] in the sequence data.
0xc4 largenoteson Set notes for this channel to use "large notes" format. SM64 does this for all channels. (See note vs. shortnote in the layer section below.)
0xc3 largenotesoff Set notes for this channel to use "short notes" format.
0xc2, addr setdyntable Set dyntable to point to a given u16 array from the sequence data.
0xc1, u8 setinstr Set instrument (program?) within bank. 0x80-0x83 set raw waves (sawtooth, triangle, sine, square), 0x7f is special, otherwise 0-indexed.
0xb0-0xbf dynsetlayer If Q != -1, start layer N, with layer script given by dyntable[Q].
0xa0-0xaf freelayer Stop layer N.
0x90-0x9f, addr setlayer Start layer N, with layer script starting at address X.
0x80-0x8f ioreadval Set Q to IO[N], where IO is an array of bytes that can be read/written by both the game and the channel script. If N < 4, IO[N] is then set to -1.
0x70-0x7f iowriteval Set IO[N] to Q.
0x60-0x6f setnotepriority Set note priority for later notes played on this channel to N. When the game wants to play a note and there aren't any free notes available, a note with smaller or equal priority is discarded. Should be >= 2; 0 and 1 have internal meaning. Defaults to 3.
0x50-0x5f ioreadvalsub Decrease Q by IO[N].
0x40-0x4f, u8 ioreadval2 Set Q to IO2[X], where IO2 is the IO array for channel N.
0x30-0x3f, u8 iowriteval2 Set IO2[X] to Q, where IO2 is the IO array for channel N.
0x20-0x2f disablechannel Disable channel N for the parent sequence.
0x10-0x1f, addr startchannel Start channel N for the parent sequence, with channel script starting at address X.
0x00-0x0f testlayerfinished Set Q to 1 or 0, depending on whether layer N has been disabled (either forcibly or by finishing its script).

Layers

(is this the right name? I've seen "track" used as well)

hex mnemonic description
0xff end End of script, loop or function
0xfc, addr call Call a function
0xfb, addr jump Jump to a point in the layer script
0xf8, u8 loop Repeat until loopend for X iterations (256 if X = 0)
0xf7 loopend Loop end marker
0xe0-0xef setshortnotedurationfromtable Set the duration for future short notes to table[N], where table defaults to {229, 203, 177, 151, 139, 126, 113, 100, 87, 74, 61, 48, 36, 23, 10, 0} and can be set by setshortnotedurationtable.
0xd0-0xdf setshortnotevelocityfromtable Set the velocity for future short notes to table[N], where table defaults to {12, 25, 38, 51, 57, 64, 71, 76, 83, 89, 96, 102, 109, 115, 121, 127} and can be set by setshortnotevelocitytable.
0xca, u8 setpan Set the pan for this layer (0..128).
0xc9, u8 setshortnoteduration Set the duration for future short notes.
0xc8 disableportamento Disable portamento for later notes.
0xc7, u8, u8, u8/var portamento Enable portamento (aka glissando; continuously sliding pitch). X describes the mode of operation somehow using its 0x80 bit and a value 0-5 in its lower-order bits. Y describes the target pitch. Z gives the duration, and is a u8 if the 0x80 bit is set, otherwise a var.
0xc6, u8 setinstr Set instrument/program. Similar to the channel command, except arguments 0x7f and above are not supported.
0xc5 somethingoff Turn off some bool related to how notes decay somehow? (This is the default.)
0xc4 somethingon Turn on the same thing.
0xc3, var setshortnotedefaultplaypercentage Set the default play percentage for short notes (see below).
0xc2, u8 transpose Set transposition in semitones.
0xc1, u8 setshortnotevelocity Set velocity for future short notes.
0xc0, var delay Delay for N ticks
0x00-0x3f, var, u8, u8 note0 Play note with play percentage X, velocity Y, duration Z and pitch N. (Is "play percentage" the right term?). Only valid if channel is set to "large notes".
0x40-0x7f, var, u8 note1 Play note with play percentage X, velocity Y, duration 0 and pitch N. Only valid if channel is set to "large notes".
0x80-0xbf, u8, u8 note2 Play note with velocity X, duration Y, pitch N and the last used play percentage. Only valid if channel is set to "large notes".
0x00-0x3f, var smallnote0 Play note with play percentage X and pitch N, with velocity and duration taken from the short notes settings set by setshortnote{velocity,duration} (or the fromtable variants), defaulting to 0 and 0x80 respectively if not set. Only valid if channel is set to "small notes".
0x40-0x7f smallnote1 Play note with pitch N and the default play percentage, as set by setshortnotedefaultplaypercentage (there is no built-in default; using it without that command will read uninitialized memory). Velocity and duration is set like in smallnote0. Only valid if channel is set to "small notes".
0x80-0xbf smallnote2 Play note with pitch N and the previous play percentage. Velocity and duration is set like in smallnote0. Only valid if channel is set to "small notes".

ADSR envelope

ADSR envelopes describe how note volume changes over time, and have the format of any number of pairs of u16's, which have to be 2-byte aligned. Volume starts at 0. Each pair is of one of the following forms:

  • 0, anything: stop the note
  • -1, anything: sustain the note indefinitely at the same volume
  • -2, index: goto that envelope table row
  • -3, anything: restart the envelope loop from the beginning, with volume 0
  • time, volume: transition to that volume over the given amount of time
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