midi1.lua

goldfiction

Dec 30th, 2023

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local component = require("component")
local computer = require("computer")
local shell = require("shell")
local keyboard = require("keyboard")
local note = require("note")
local bit32 = require("bit32")
local args, options = shell.parse(...)
if #args < 1 then
print("Usage: midi [-i] <filename> [track1 [track2 [...]]]")
print("Where the tracks are the numbers of the tracks to actually play.")
print(" -i: only parse and show track info, don't play.")
return
end
-- Implements the essentials for MIDI file parsing, references:
-- http://www.recordingblogs.com/sa/tabid/88/Default.aspx?topic=Musical+Instrument+Digital+Interface+(MIDI)
-- http://www.sonicspot.com/guide/midifiles.html
local enabledTracks = {n=0}
for i = 2, #args do
enabledTracks[tonumber(args[i])] = true
enabledTracks.n = enabledTracks.n + 1
end
local instruments = {}
for address in component.list("note_block") do
table.insert(instruments, function(note)
-- 60 = C in MIDI, 6 = C in Minecraft
component.invoke(address, "trigger", (note + 6 - 60) % 24 + 1)
end)
end
if #instruments == 0 then
local function beepableFrequency(midiCode)
local freq = note.freq(midiCode)
if freq <= 0 then error("Nonpositive frequency") end
-- shift it by octaves so we at least get the right pitch
while freq < 20 do freq = freq * 2 end
while freq > 2000 do freq = freq / 2 end
return freq
end
if component.isAvailable("beep") then
print("No note blocks found, falling back to beep card.")
local notes = {}
instruments[1] = function(note, duration)
notes[beepableFrequency(note)] = duration or 0.05
end
instruments.flush = function()
component.beep.beep(notes)
for k, v in pairs(notes) do
notes[k] = nil
end
end
else
print("No note blocks or beep card found, falling back to built-in speaker.")
instruments[1] = function(note, duration)
pcall(computer.beep, beepableFrequency(note), duration or 0.05)
return true -- only one event per tick
end
end
else
print("Using " .. #instruments .. " note blocks.")
end
local filename = shell.resolve(args[1])
local f, reason = io.open(filename, "rb")
if not f then
print(reason)
return
end
local function parseVarInt(s, bits) -- parses multiple bytes as an integer
if not s then
error("error parsing file")
end
bits = bits or 8
local mask = bit32.rshift(0xFF, 8 - bits)
local num = 0
for i = 1, s:len() do
num = num + bit32.lshift(bit32.band(s:byte(i), mask), (s:len() - i) * bits)
end
return num
end
local function readChunkInfo() -- reads chunk header info
local id = f:read(4)
if not id then
return
end
return id, parseVarInt(f:read(4))
end
-- Read the file header and with if file information.
local id, size = readChunkInfo()
if id ~= "MThd" or size ~= 6 then
print("error parsing header (" .. id .. "/" .. size .. ")")
return
end
local format = parseVarInt(f:read(2))
local tracks = parseVarInt(f:read(2))
local delta = parseVarInt(f:read(2))
if format < 0 or format > 2 then
print("unknown format")
return
end
local formatName = ({"single", "synchronous", "asynchronous"})[format + 1]
print(string.format("Found %d %s tracks.", tracks, formatName))
if format == 2 then
print("Sorry, asynchronous tracks are not supported.")
return
end
-- Figure out our time system and prepare accordingly.
local time = {division = bit32.band(0x8000, delta) == 0 and "tpb" or "fps"}
if time.division == "tpb" then
time.tpb = bit32.band(0x7FFF, delta)
time.mspb = 500000
function time.tick()
return time.mspb / time.tpb
end
print(string.format("Time division is in %d ticks per beat.", time.tpb))
else
time.fps = bit32.band(0x7F00, delta)
time.tpf = bit32.band(0x00FF, delta)
function time.tick()
return 1000000 / (time.fps * time.tpf)
end
print(string.format("Time division is in %d frames per second with %d ticks per frame.", time.fps, time.tpf))
end
function time.calcDelay(later, earlier)
return (later - earlier) * time.tick() / 1000000
end
-- Parse all track chunks.
local totalOffset = 0
local totalLength = 0
local tracks = {}
while true do
local id, size = readChunkInfo()
if not id then
break
end
if id == "MTrk" then
local track = {}
local cursor = 0
local start, offset = f:seek(), 0
local inSysEx = false
local running = 0
local function read(n)
n = n or 1
if n > 0 then
offset = offset + n
return f:read(n)
end
end
local function readVariableLength()
local total = ""
for i = 1, math.huge do
local part = read()
total = total .. part
if bit32.band(0x80, part:byte(1)) == 0 then
return parseVarInt(total, 7)
end
end
end
local function parseVoiceMessage(event)
local channel = bit32.band(0xF, event)
local note = parseVarInt(read())
local velocity = parseVarInt(read())
return channel, note, velocity
end
local currentNoteEvents = {}
local function noteOn(cursor, channel, note, velocity)
track[cursor] = {channel, note, velocity}
if not currentNoteEvents[channel] then
currentNoteEvents[channel] = {}
end
currentNoteEvents[channel][note] = {event=track[cursor], tick=cursor}
end
local function noteOff(cursor, channel, note, velocity)
if not (currentNoteEvents[channel] and currentNoteEvents[channel][note]) then return end
table.insert(currentNoteEvents[channel][note].event
, time.calcDelay(cursor, currentNoteEvents[channel][note].tick))
currentNoteEvents[channel][note] = nil
end
while offset < size do
cursor = cursor + readVariableLength()
totalLength = math.max(totalLength, cursor)
local test = parseVarInt(read())
if inSysEx and test ~= 0xF7 then
error("corrupt file: could not find continuation of divided sysex event")
end
local event
if bit32.band(test, 0x80) == 0 then
if running == 0 then
error("corrupt file: invalid running status")
end
f.bufferRead = string.char(test) .. f.bufferRead
offset = offset - 1
event = running
else
event = test
if test < 0xF0 then
running = test
end
end
local status = bit32.band(0xF0, event)
if status == 0x80 then -- Note off.
local channel, note, velocity = parseVoiceMessage(event)
noteOff(cursor, channel, note, velocity)
elseif status == 0x90 then -- Note on.
local channel, note, velocity = parseVoiceMessage(event)
if velocity == 0 then
noteOff(cursor, channel, note, velocity)
else
noteOn(cursor, channel, note, velocity)
end
elseif status == 0xA0 then -- Aftertouch / key pressure
parseVoiceMessage(event) -- not handled
elseif status == 0xB0 then -- Controller
parseVoiceMessage(event) -- not handled
elseif status == 0xC0 then -- Program change
parseVarInt(read()) -- not handled
elseif status == 0xD0 then -- Channel pressure
parseVarInt(read()) -- not handled
elseif status == 0xE0 then -- Pitch / modulation wheel
parseVarInt(read(2), 7) -- not handled
elseif event == 0xF0 then -- System exclusive event
local length = readVariableLength()
if length > 0 then
read(length - 1)
inSysEx = read(1):byte(1) ~= 0xF7
end
elseif event == 0xF1 then -- MIDI time code quarter frame
parseVarInt(read()) -- not handled
elseif event == 0xF2 then -- Song position pointer
parseVarInt(read(2), 7) -- not handled
elseif event == 0xF3 then -- Song select
parseVarInt(read(2), 7) -- not handled
elseif event == 0xF7 then -- Divided system exclusive event
local length = readVariableLength()
if length > 0 then
read(length - 1)
inSysEx = read(1):byte(1) ~= 0xF7
else
inSysEx = false
end
elseif event >= 0xF8 and event <= 0xFE then -- System real-time event
-- not handled
elseif event == 0xFF then
-- Meta message.
local metaType = parseVarInt(read())
local length = parseVarInt(read())
local data = read(length)
if metaType == 0x00 then -- Sequence number
track.sequence = parseVarInt(data)
elseif metaType == 0x01 then -- Text event
elseif metaType == 0x02 then -- Copyright notice
elseif metaType == 0x03 then -- Sequence / track name
track.name = data
elseif metaType == 0x04 then -- Instrument name
track.instrument = data
elseif metaType == 0x05 then -- Lyric text
elseif metaType == 0x06 then -- Marker text
elseif metaType == 0x07 then -- Cue point
elseif metaType == 0x20 then -- Channel prefix assignment
elseif metaType == 0x2F then -- End of track
track.eot = cursor
elseif metaType == 0x51 then -- Tempo setting
track[cursor] = parseVarInt(data)
elseif metaType == 0x54 then -- SMPTE offset
elseif metaType == 0x58 then -- Time signature
elseif metaType == 0x59 then -- Key signature
elseif metaType == 0x7F then -- Sequencer specific event
end
else
f:seek("cur", -9)
local area = f:read(16)
local dump = ""
for i = 1, area:len() do
dump = dump .. string.format(" %02X", area:byte(i))
if i % 4 == 0 then
dump = dump .. "\n"
end
end
error(string.format("midi file contains unhandled event types:\n0x%X at offset %d/%d\ndump of the surrounding area:\n%s", event, offset, size, dump))
end
end
-- turn off any remaining notes
for iChannel, iNotes in pairs(currentNoteEvents) do
for iNote, iEntry in pairs(currentNoteEvents[iChannel]) do
noteOff(cursor, iChannel, iNote)
end
end
local delta = size - offset
if delta ~= 0 then
f:seek("cur", delta)
end
totalOffset = totalOffset + size
table.insert(tracks, track)
else
print(string.format("Encountered unknown chunk type %s, skipping.", id))
f:seek("cur", size)
end
end
f:close()
if options.i then
print(string.format("Found %d tracks, total length is %d ticks.", #tracks, totalLength))
for i, track in ipairs(tracks) do
if track.name then
print(string.format("#%d: %s", i, track.name))
end
end
return
end
local removed = 0
if enabledTracks.n > 0 then
for i = #tracks, 1, -1 do
if not enabledTracks[i] then
table.remove(tracks, i)
removed = removed + 1
end
end
end
print("Playing " .. #tracks .. " tracks:")
for _, track in ipairs(tracks) do
if track.name then
print(string.format("%s", track.name))
end
end
local channels = {n=0}
local lastTick, lastTime = 0, computer.uptime()
print("Press Ctrl+C to exit.")
for tick = 1, totalLength do
local hasEvent = false
for _, track in ipairs(tracks) do
if track[tick] then
hasEvent = true
break
end
end
if hasEvent then
local delay = time.calcDelay(tick, lastTick)
-- delay % 0.05 == 0 doesn't seem to work
if math.floor(delay * 100 + 0.5) % 5 == 0 then
os.sleep(delay)
else
-- Busy idle otherwise, because a sleep will take up to 50ms.
local begin = os.clock()
while os.clock() - begin < delay do end
end
lastTick = tick
lastTime = computer.uptime()
for _, track in ipairs(tracks) do
local event = track[tick]
if event then
if type(event) == "number" then
time.mspb = event
elseif type(event) == "table" then
local channel, note, velocity, duration = table.unpack(event)
local instrument
if not channels[channel] then
channels.n = channels.n + 1
channels[channel] = instruments[1 + (channels.n % #instruments)]
end
if channels[channel](note, duration) then
break
end
end
end
end
if instruments.flush then instruments.flush() end
end
if keyboard.isKeyDown(keyboard.keys.c) and keyboard.isControlDown() then os.exit() end
end

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