BBC MicroのENVELOPEコマンドでなる音階をExcelのグラフに書き出します。

envelope.rb

require 'caxlsx'

# envelope's parameter no
ENV_N     = 0
ENV_T     = 1
ENV_PI1   = 2
ENV_PI2   = 3
ENV_PI3   = 4
ENV_PN1   = 5
ENV_PN2   = 6
ENV_PN3   = 7
ENV_AA    = 8
ENV_AD    = 9
ENV_AS    = 10
ENV_AR    = 11
ENV_ALA   = 12
ENV_ALD   = 13

# sound's parameter no
SND_C     = 0
SND_A     = 1
SND_P     = 2
SND_D     = 3

# commands
lines =<<EOS
ENVELOPE 2,1,2,-2,2,10,20,10,1,0,0,-1,100,100
SOUND 1,2,100,100
EOS

# divide commands to parameters
lines.each_line do |l|
  case l.scan(/\w+/).first.upcase
  when "ENVELOPE"
    @envelope = l.scan(/\-?\d+/).to_a.map(&:to_i)
  when "SOUND"
    @sound = l.scan(/\-?\d+/).to_a.map(&:to_i)
  end
end

# pitch pattern
@pitch = [@sound[SND_P]]
[
  [ENV_PI1, ENV_PN1],
  [ENV_PI2, ENV_PN2],
  [ENV_PI3, ENV_PN3],
].each do |pi,ni|
  @envelope[ni].times do
    @pitch << @pitch.last + @envelope[pi]
  end
end

# make envelope of amplitued
@duration = @sound[SND_D] / 20.0
@time = 0
@t_delta = @envelope[ENV_T] / 100.0

@amplitude = [0]
while @time < @duration && @amplitude.last < @envelope[ENV_ALA]
  @amplitude << [@amplitude.last + @envelope[ENV_AA], @envelope[ENV_ALA]].min
  @time += @t_delta
end
while @time < @duration && @amplitude.last > @envelope[ENV_ALD]
  @amplitude << [@amplitude.last + @envelope[ENV_AD], 0].max
  @time += @t_delta
end
while @time < @duration
  @amplitude << [@amplitude.last + @envelope[ENV_AS], 0].max
  @time += @t_delta
end
while @amplitude.last > 0 && @envelope[ENV_AR] < 0
  @amplitude << [@amplitude.last + @envelope[ENV_AR], 0].max
  @time += @t_delta
end

# generate excel file
p = Axlsx::Package.new
p.workbook.add_worksheet(:name => "Pitch") do |sheet|
  sheet.add_row ["ENVELOPE"] + @envelope
  sheet.add_row ["SOUND"] + @sound
  sheet.add_row []
  sheet.add_row ["TIME", "PITCH", "AMPLITUDE"]

  # fill data cells
  c = @amplitude.size
  cp = @pitch.size
  @time = 0
  c.times do |i|
    sheet.add_row [@time, @pitch[i % cp], @amplitude[i]]
    @time += @t_delta
  end

  # add chard
  sheet.add_chart(Axlsx::ScatterChart, title: "PITCH & AMPLITUDE", start_at: 'E5', end_at: 'R25') do |chart|
    chart.add_series xData: sheet["A5:A#{(5 - 1) + c}"], yData: sheet["B5:B#{(5 - 1) + c}"], title: sheet['B4']
    chart.add_series xData: sheet["A5:A#{(5 - 1) + c}"], yData: sheet["C5:C#{(5 - 1) + c}"], title: sheet['C4']
  end
end

p.use_shared_strings = true
p.serialize('envelope.xlsx')

envelope.xlsx

Gemfile

# frozen_string_literal: true

source "https://rubygems.org"

git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }

gem "caxlsx"