mixlr.rb

require 'json'
require 'open-uri'
require 'open3'

STREAMS_URL = 'https://mixlr-codetest.herokuapp.com/stations/netil-radio/streams'

body = URI.open(STREAMS_URL).read
json = JSON.parse(body)

volumes = json.dig('data', 'attributes', 'streams').map do |stream_name, url|
  _, stderr, process_info = Open3.capture3('ffmpeg', '-t', '3', '-i', url, '-af', 'volumedetect', '-f', 'null', '/dev/null')

  mean_volume = stderr.match(/mean_volume: (.*) dB/)[1].to_f
  max_volume = stderr.match(/max_volume: (.*) dB/)[1].to_f

  {stream_name:, mean_volume:, max_volume:}
end

puts JSON.pretty_generate(volumes)