RadioPi

RadioPi is the web radio of the ECP (Ecole Centrale de Paris). RadioPi runs many channels. There are topical channels (Reggae, Hip-Hop, Jazz, …). On top of that, they periodically broadcast live shows, which are relayed on all channels.

We met a RadioPi manager right after having released Liquidsoap 0.2.0, and he was seduced by the system. They needed quite complex features, which they were at that time fulfilling using dirty tricks, loads of obfuscated scripts. Using Liquidsoap now allow them to do all they want in an integrated way, but also provided new features.

The migration process

Quite easy actually. They used to have many instances Ices2, each of these calling a Perl script to get the next song. Other scripts were used for switching channels to live shows.

Now they have this single Liquidsoap script, no more. It calls external scripts to interact with their web-based song scheduling system. And they won new features: blank detection and distributed encoding.

The first machine gets its files from a ftp server opened on the second machine. Liquidsoap handles download automatically.

Each file is given by an external script, radiopilote-getnext, whose answer looks as follows (except that it’s on a single line):

annotate:file_id="3541",length="400.613877551",\
    type="chansons",title="John Holt - Holigan",\
    artist="RadioPi - Canal reggae",\
    album="Studio One SeleKta! - Album Studio 1 12",\
    canal="reggae":ftp://***:***@host/files/3541.mp3

Note that we use annotate to pass some variables to liquidsoap…

#!/usr/bin/liquidsoap
  
  # Standard settings
  log.file.set(true)
  log.file.path.set("/var/log/liquidsoap/pi.log")
  log.stdout.set(false)
  init.daemon.set(true)
  init.daemon.pidfile.path.set("/var/run/liquidsoap/pi.pid")
  
  # Enable telnet server
  settings.server.telnet.set(true)
  
  # Enable harbor for any external
  # connection
  settings.harbor.bind_addrs.set(["0.0.0.0"])
  
  # Verbose logs
  log.level.set(4)
  
  # We use the scheduler intensively,
  # therefore we create many queues.
  settings.scheduler.generic_queues.set(5)
  settings.scheduler.fast_queues.set(3)
  settings.scheduler.non_blocking_queues.set(3)
  
  # === Settings ===
  
  # The host to request files
  stream = "XXXxXXXx"
  # The command to request files
  scripts = "ssh XXxxxXXX@#{stream} '/path/to/scripts/"
  # A substitution on the returned path
  sed = " | sed -e s#/path/to/files/#ftp://user:password@#{stream}/#'"
  
  # Enable replay gain
  enable_replaygain_metadata ()
  
  pass = "XXxXXXXx"
  ice_host = "localhost"
  
  descr = "RadioPi"
  url = "http://radiopi.org"
  
  # === Live ===
  
  # A live source, on which we stip blank (make the source
  # unavailable when streaming blank)
  live = 
    blank.strip(
      input.harbor(id="live", port=8000, password=pass,
                   buffer=8.,max=20.,"live.ogg"),
      length=10., threshold=-50.)
  
  # This source relays the live data, when available,
  # to the other streamer, in uncompressed format (WAV)
  output.icecast(%wav, host=stream,
                 port=8005, password=pass,
                 mount="live.ogg", fallible=true,
                 live)
  
  # This source relays the live source to "live.ogg". This 
  # is used for debugging purposes, to see what is sent
  # to the harbor source.
  output.icecast(%vorbis, host="127.0.0.1",
                 port=8080, password=pass, 
                 mount="live.ogg", fallible=true,
                 live)
  
  # This source starts an archive of the live stream
  # when available
  title = '$(if $(title),"$(title)",\
           "Emission inconnue")$(if $(artist), \
           " par  $(artist)") - %m-%d-%Y, %H:%M:%S'
  output.file(%vorbis, reopen_on_metadata=true,
              fallible=true,
              "/data/archives/brutes/" ^ title ^ ".ogg",
              live)
  
  # === Channels ===
  
  # Specialize the output functions by partial application
  output.icecast = output.icecast(description=descr, url=url)
  out = output.icecast(host=ice_host,port=8080,password=pass,fallible=true)
  out_aac32 = out(%fdkaac(bitrate=32))
  out_aac = out(%fdkaac(bitrate=64))
  out = out(%mp3)
  
  # A file for playing during failures
  interlude =
    single("/home/radiopi/fallback.mp3")
  
  # Lastfm submission
  def lastfm (m) = 
    if (m["type"] == "chansons") then
      if (m["canal"] == "reggae" or m["canal"] == "Jazz" or m["canal"] == "That70Sound") then
        canal = 
          if (m["canal"] == "That70Sound") then 
         "70sound" 
      else 
         m["canal"]
      end
        user = "radiopi-" ^ canal
        lastfm.submit(user=user,password="xXXxx",m)
      end
    end
  end 
  
  # === Basic sources ===
  
  # Custom crossfade to deal with jingles..
  def crossfade (~start_next=5.,~fade_in=3.,~fade_out=3.,
                 ~default=(fun (a,b) -> sequence([a, b])),
                 ~high=-15., ~medium=-32., ~margin=4.,
                 ~width=2.,~conservative=false,s)
    fade.out = fade.out(type="sin",duration=fade_out)
    fade.in  = fade.in(type="sin",duration=fade_in)
    add = fun (a,b) -> add(normalize=false,[b, a])
    log = log(label="crossfade")
  
    def transition(a,b,ma,mb,sa,sb)
  
      list.iter(fun(x)-> log(level=4,"Before: #{x}"),ma)
      list.iter(fun(x)-> log(level=4,"After : #{x}"),mb)
  
      if ma["type"] == "jingles" or mb["type"] == "jingles" then
        log("Old or new file is a jingle: sequenced transition.")
        sequence([sa, sb])
      elsif
        # If A and B are not too loud and close, fully cross-fade them.
        a <= medium and b <= medium and abs(a - b) <= margin
      then
        log("Old <= medium, new <= medium and |old-new| <= margin.")
        log("Old and new source are not too loud and close.")
        log("Transition: crossed, fade-in, fade-out.")
        add(fade.out(sa),fade.in(sb))
  
      elsif
        # If B is significantly louder than A, only fade-out A.
        # We don't want to fade almost silent things, ask for >medium.
        b >= a + margin and a >= medium and b <= high
      then
        log("new >= old + margin, old >= medium and new <= high.")
        log("New source is significantly louder than old one.")
        log("Transition: crossed, fade-out.")
        add(fade.out(sa),sb)
  
      elsif
        # Opposite as the previous one.
        a >= b + margin and b >= medium and a <= high
      then
        log("old >= new + margin, new >= medium and old <= high")
        log("Old source is significantly louder than new one.")
        log("Transition: crossed, fade-in.")
        add(sa,fade.in(sb))
  
      elsif
        # Do not fade if it's already very low.
        b >= a + margin and a <= medium and b <= high
      then
        log("new >= old + margin, old <= medium and new <= high.")
        log("Do not fade if it's already very low.")
        log("Transition: crossed, no fade.")
        add(sa,sb)
  
      # What to do with a loud end and a quiet beginning ?
      # A good idea is to use a jingle to separate the two tracks,
      # but that's another story.
  
      else
        # Otherwise, A and B are just too loud to overlap nicely,
        # or the difference between them is too large and overlapping would
        # completely mask one of them.
        log("No transition: using default.")
        default(sa, sb)
      end
    end
  
    cross(width=width, duration=start_next, conservative=conservative,
                transition,s)
  end
  
  # Create a radiopilote-driven source
  def channel_radiopilote(~skip=true,name)
    log("Creating canal #{name}")
    
    # Request function
    def request () = 
      log("Request for #{name}")
      ret = list.hd(process.read.lines(scripts^"radiopilote-getnext "^quote(name)^sed))
      log("Got answer: #{ret} for #{name}")
      [request.create(ret)]
    end
  
    # Create the request.dynamic.list source
    # Set conservative to true to queue
    # several songs in advance
    source = 
      request.dynamic.list(conservative=true, length=400.,
                      id="dyn_"^name,request, 
                      timeout=60.)
   
    # Apply normalization using replaygain 
    # information
    source =   amplify(1.,override="replay_gain", source)
  
    # Skip blank when asked to
    source = 
      if skip then
        blank.skip(source, length=10., threshold=-40.)
      else
        source
      end
  
    # Submit new tracks on lastfm
    source = on_metadata(lastfm,source)
    
    # Tell the system when a new track
    # is played
    source = on_metadata(fun (meta) ->
                      system(scripts ^ "radiopilote-feedback "
                             ^quote(meta["canal"])^" "
                             ^quote(meta["file_id"]) ^ "'"), source)
  
    # Finally apply a smart crossfading
    crossfade(source)
  end
  
  # Basic source
  jazz = channel_radiopilote("jazz")
  discoqueen = channel_radiopilote("discoqueen")
  # Avoid skipping blank with classic music !!
  classique = channel_radiopilote(skip=false,"classique")
  That70Sound = channel_radiopilote("That70Sound")
  metal = channel_radiopilote("metal")
  reggae = channel_radiopilote("reggae")
  Rock = channel_radiopilote("Rock")
  
  # Group those sources in a separate
  # clock (good for multithreading/multicore)
  clock.assign_new([jazz,That70Sound,metal,reggae])
  
  # === Mixing live ===
  
  # To create a channel from a basic source, add:
  # - a new-track notification for radiopilote
  # - metadata rewriting
  # - the live shows
  # - the failsafe 'interlude' source to channels
  # - blank detection
  def mklive(source) =
    # Transition function: if transitioning
    # to the live, fade out the old source
    # if transitioning from live, fade.in 
    # the new source. NOTE: We cannot
    # skip the current song because
    # reloading new songs for all the
    # sources when live starts costs too much
    # CPU.
    def trans(old,new) =
      if source.id(new) == source.id(live) then 
        log("Transition to live!")
        add([new,fade.out(old)])
      elsif source.id(old) == source.id(live) then
        log("Transitioning from live!")
        add([fade.in(new),old])    
      else
        log("Dummy transition")
        new
      end
    end
    fallback(track_sensitive=false,
      transitions=[trans,trans,trans],
      [live,source,interlude])
  end
  
  # Create a channel using mklive(), encode and output it to icecast.
  def mkoutput(~out=out,mount,source,name,genre)
    out(id=mount,mount=mount,name=name,genre=genre,
       mklive(source)
       )
  end
  
  # === Outputs ===
  
  mkoutput("jazz", jazz, "RadioPi - Canal Jazz","jazz")
  mkoutput("discoqueen", discoqueen, "RadioPi - Canal DiscoQueen","discoqueen")
  mkoutput("classique", classique, "RadioPi - Canal Classique","classique")
  mkoutput("That70Sound", That70Sound,
                         "RadioPi - Canal That70Sound","That70Sound")
  mkoutput("metal", metal, "RadioPi - Canal Metal","metal")
  mkoutput("reggae", reggae, "RadioPi - Canal Reggae","reggae")
  mkoutput("Rock", Rock, "RadioPi - Canal Rock","Rock")
  
  # Test outouts
  mkoutput(out=out_aac,"reggae.aacp", reggae, "RadioPi - Canal Reggae \
                                       (64 kbits AAC+ test stream)","reggae")
  mkoutput(out=out_aac32,"reggae.aacp32", reggae, "RadioPi - Canal Reggae \
                                        (32 kbits AAC+ test stream)","reggae")

The other machine has a similar configuration except that files are local, but this is exactly the same for liquidsoap !

Using harbor, the live connects directly to liquidsoap, using port 8000 (icecast runs on port 8080). Then, liquidsoap starts a relay to the other encoder, and both switch their channels to the new live.

Additionally, a file output is started upon live connection, in order to backup the stream. You could also add a relay to icecast in order to manually check what’s received by the harbor.