A complete case analysis

We will develop here a more complex example, according to the following specifications:

• play different playlists during the day;
• play user requests -- done via the telnet server;
• insert about 1 jingle every 5 songs;
• add one special jingle at the beginning of every hour, mixed on top of the normal stream;
• relay live shows as soon as one is available;
• and set up several outputs.

Once you can describe what you want in such a modular way, you're halfway there. Think of the diagram below as a graph through which the audio stream flows, following the arrows. The nodes modify the stream using basic operators: switching and mixing in our case. The final nodes are outputs: they pull data out of the graph and send it to the world. In our case, we have three Icecast outputs: the full stream in MP3 and Ogg/Vorbis, and the stream without live shows in Ogg/Vorbis.

Now here is how to write that in Liquidsoap.

complete-case.liq

#!/usr/bin/liquidsoap

# Lines starting with # are comments, they are ignored.

# Put the log file in some directory where you have permission to write.
log.file.path := "/tmp/<script>.log"

# Print log messages to the console, can also be done by passing the -v option
# to Liquidsoap.
log.stdout := true

# Use the telnet server for requests
settings.server.telnet := true

# A bunch of files and playlists, supposedly all located in the same base dir.
default = single("~/radio/default.ogg")

day = playlist("~/radio/day.pls")
night = playlist("~/radio/night.pls")
jingles = playlist("~/radio/jingles.pls")
clock = single("~/radio/clock.ogg")

# Play user requests if there are any, otherwise one of our playlists, and the
# default file if anything goes wrong.
radio =
  fallback(
    [
      request.queue(id="request"),
      switch([({6h-22h}, day), ({22h-6h}, night)]),
      default
    ]
  )

# Add the normal jingles
radio = random([jingles.{weight = 1}, radio.{weight = 5}])

# And the clock jingle
radio = add([radio, switch([({0m0s}, clock)])])

radio = mksafe(radio)

# Add the ability to relay live shows
full = fallback([input.http("http://localhost:8000/live.ogg"), radio])

# Output the full stream in OGG and MP3
output.icecast(
  %mp3,
  host="localhost",
  port=8000,
  password="hackme",
  mount="radio",
  full
)
output.icecast(
  %vorbis,
  host="localhost",
  port=8000,
  password="hackme",
  mount="radio.ogg",
  full
)

# Output the stream without live in OGG
output.icecast(
  %vorbis,
  host="localhost",
  port=8000,
  password="hackme",
  mount="radio_nolive.ogg",
  radio
)

To try this example, you'll need to edit the file names. To see the playlist switch in action, adjust the time intervals. If it's currently 16:42, try 0h-16h45 and 16h45-24h instead of 6h-22h and 22h-6h. To test the hourly jingle, you can trigger it every minute by using the 0s interval instead of 0m0s.

To test the transition to a live show, start a new stream on the live.ogg mount of your server. You can use the examples from the quickstart to stream a playlist to it. To start a real live show from soundcard input, use darkice, or simply liquidsoap if you have a working ALSA input:

liquidsoap 'output.icecast(%vorbis, \
  mount="live.ogg",host="...",password="...",input.alsa())'