app/services/audio_uploader.rb

audio_uploader.rb

class AudioUploader
  # ctor takes a logged-in user (ActiveRecord) and path to a temp WAV
  def initialize(user, tmpfile_path)
    @user         = user                           # e.g. <User id:1>
    @tmpfile_path = tmpfile_path                   # e.g. "/tmp/input.wav"
    @s3_client    = Aws::S3::Client.new(region: "ap-northeast-1")
  end

  # -- master workflow (all side-effects inline) ---------------------------

  def run
    # 1) convert WAV → MP3 (128 kbps, CBR)
    system("ffmpeg -y -i #{@tmpfile_path} " \
           "-codec:a libmp3lame -b:a 128k /tmp/out.mp3")

    # 2) measure integrated loudness (LUFS) with ffprobe/loudnorm
    loudness = `ffmpeg -i /tmp/out.mp3 -af loudnorm=I=-14:TP=-1.5:LRA=11 \
                -f null - 2>&1 | grep "I:" | tail -1 | awk '{print $2}'`.to_f

    # 3) upload to S3 (blocking call)
    bucket = ENV.fetch("AUDIO_BUCKET", "my-demo-bucket")
    key    = "tracks/#{SecureRandom.uuid}.mp3"
    @s3_client.put_object(bucket: bucket,
                          key:    key,
                          body:   File.open("/tmp/out.mp3", "rb"))

    # 4) persist track + send “ready” e-mail
    track = @user.audio_tracks.create!(
      s3_key:        key,
      status:        "ready",
      loudness_lufs: loudness
    )

    AudioMailer.with(user: @user, track: track).ready.deliver_now
  end
end