Many of the advanced features of the Liquidsoap language are described in Liquidsoap: a High-Level Programming Language for Multimedia Streaming. The article details in particular Liquidsoap’s handling of heterogeneous stream contents (e.g. audio and video), as well as the model for clocks in the language.
The first published presentation of Liquidsoap was made in De la webradio lambda à la λ-webradio (Baelde D. and Mimram S. in proceedings of Journées Francophnes des Languages Applicatifs (JFLA), pages 47-61, 2008) – yes, it’s in French, sorry. It gives a broad description of the Liquidsoap tool and explains the theory behind the language, which is formalized as a variant of the typed λ-calculus with labels and optional arguments. The article describes the typing inference algorithm as well as some properties of the language (confluence) and of typing (subject reduction, admissible rules, termination of typed terms).