Liquidsoap

Liquidsoap is a scripting language oriented toward the creation of audio and video streams, the manipulation of multimedia files, automation, serving as webserver back-end and more. The language is functional, statically typed with type inference.[1] The language is an original one, but the interpreter is programmed in OCaml and provided as free software.

Developer(s)Romain Beauxis and Samuel Mimram
Initial release2004
Stable release
2.2.0
Repositorygithub.com/savonet/liquidsoap
Written inOCaml
Operating systemUnix-like and Microsoft Windows
TypeStream generator
LicenseGPL-2.0-or-later
Websitewww.liquidsoap.info

Streams can be created from various sources such as soundcard captures, playlists, dynamic requests, or online streams. On those signal processing effects can be applied. The streams can be encoded in various formats such as MP3 or Opus,[2] and the actual streaming is performed by serving generated HLS playlists or by using streaming software such as Icecast.[3] Although originally targeted at audio streams, the generation of video stream is also supported.[4]

Usage

Liquidsoap is used as a back-end for radio streaming software such as Airtime,[5] AzuraCast[6] or LibreTime.[7] It is also used by many radios to generate online streams such as the French national radio Radio France,[8][9][10] or the Live365 radio network.[11][12]

Script examples

Scripts mostly consist of variables describing sources generating streams, which can be combined using operators.

For instance, a source can be defined from an online stream by

s1 = input.http("https://server.org:8000/stream")

which can later on be amplified by

s1 = amplify(2., s1)

A source can also be defined from a playlist by

s2 = playlist("my_playlist")

A source which will play one or the other of the above sources depending on the time of the day can be created by

s = switch[({ 6h-22h }, s1), ({ 22h-6h }, s2)]

Finally, the resulting source can be broadcast by an Icecast server as an mp3 stream with

output.icecast(%mp3, host="localhost", port=8000, password="hackme", mount="radio", s)

References
  1. Baelde, David; Beauxis, Romain; Mimram, Samuel (2011). "Liquidsoap: A High-Level Programming Language for Multimedia Streaming". SOFSEM 2011: Theory and Practice of Computer Science. Lecture Notes in Computer Science. Vol. 6543. pp. 99–110. arXiv:1104.2681. doi:10.1007/978-3-642-18381-2_8. ISBN 978-3-642-18380-5. S2CID 1250366.
  2. "Creating an Internet Radio Station with Icecast and Liquidsoap".
  3. "Icecast 3rd Party Applications".
  4. "Functional audio and video stream generation with Liquidsoap".
  5. "What is Airtime?".
  6. "AzuraCast".
  7. "LibreTime architecture".
  8. "Radio France contributes to open source audio streaming software".
  9. "Building an Open-Source based audio streaming platform".
  10. "Radio France's Liquidsoap scripts". GitHub.
  11. "Live365 to Present at Liquidshop 1.0".
  12. "Live365 to Showcase Product at Liquidshop 2".

Further reading
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