65 lines
1.9 KiB
Elixir
65 lines
1.9 KiB
Elixir
defmodule MIDITools.Event do
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@moduledoc """
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Several musical events which can be converted to MIDI commands.
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All timings are in milliseconds.
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"""
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defmodule Note do
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@moduledoc """
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An event which plays the given tone for the given timespan.
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"""
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defstruct channel: 0, tone: 0, start_time: 0, end_time: 0, velocity: 0
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@spec new(MIDISynth.Command.channel(), non_neg_integer(), non_neg_integer(), non_neg_integer(), MIDISynth.Command.velocity()) :: %Note{}
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def new(channel, tone, start_time, end_time, velocity) when start_time >= 0 and end_time > start_time do
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%__MODULE__{
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channel: channel,
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tone: tone,
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start_time: start_time,
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end_time: end_time,
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velocity: velocity
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}
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end
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end
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defmodule ChangeProgram do
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@moduledoc """
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An event which changes the current program of the given channel.
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"""
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defstruct channel: 0, time: 0, program: 0
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@spec new(MIDISynth.Command.channel(), non_neg_integer(), non_neg_integer()) :: %ChangeProgram{}
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def new(channel, time, program) do
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%__MODULE__{channel: channel, time: time, program: program}
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end
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end
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@typedoc """
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A musical event.
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"""
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@type t :: %Note{} | %ChangeProgram{}
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@doc """
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Converts the event to a list of MIDI commands.
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"""
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@spec convert(t()) :: [{non_neg_integer(), binary()}]
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def convert(%Note{
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channel: channel,
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tone: tone,
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start_time: start_time,
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end_time: end_time,
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velocity: velocity
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}) do
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note_on = MIDISynth.Command.note_on(channel, tone, velocity)
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note_off = MIDISynth.Command.note_off(channel, tone)
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[{start_time, note_on}, {end_time, note_off}]
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end
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def convert(%ChangeProgram{channel: channel, time: time, program: program}) do
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change_program = MIDISynth.Command.change_program(channel, program)
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[{time, change_program}]
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end
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end
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