Add Liquidsoap ffmpeg plugin

In order to correctly decode 32-bits float WAV files, Liquidsoap ffmpeg plugin is needed.

This commit adds a new opam dependency (ocaml-ffmpeg), and multiple ffmpeg libraries.

The disco repository config has been commented out, because it was interfering with ffmpeg
installation, and it seems to work fine without it.

Dockerfile

@@ -7,8 +7,8 @@ FROM ubuntu:bionic AS base
 ENV TZ="UTC"
 
 # Add source for libopus from Ubuntu 19.04
-COPY ./disco.list /etc/apt/sources.list.d/disco.list
-COPY ./disco /etc/apt/preferences.d/disco
+#COPY ./disco.list /etc/apt/sources.list.d/disco.list
+#COPY ./disco /etc/apt/preferences.d/disco
 
 # Run base build process
 COPY ./build/ /bd_build
@@ -42,7 +42,8 @@ USER azuracast
 
 RUN opam init --disable-sandboxing -a --bare && opam switch create 4.08.0 
 
-ARG opam_packages="samplerate.0.1.4 taglib.0.3.3 mad.0.4.5 faad.0.4.0 fdkaac.0.3.1 lame.0.3.3 vorbis.0.7.1 cry.0.6.1 flac.0.1.5 opus.0.1.3 duppy.0.8.0 ssl liquidsoap.1.4.1"
+
+ARG opam_packages="ffmpeg.0.4.1 samplerate.0.1.4 taglib.0.3.3 mad.0.4.5 faad.0.4.0 fdkaac.0.3.1 lame.0.3.3 vorbis.0.7.1 cry.0.6.1 flac.0.1.5 opus.0.1.3 duppy.0.8.0 ssl liquidsoap.1.4.1"
 RUN opam install -y ${opam_packages}
 
 #

build/setup/liquidsoap.sh

@@ -5,4 +5,5 @@ set -x
 
 # Only install Liquidsoap deps (Liquidsoap build is handled by another container).
 $minimal_apt_get_install libfaad-dev libfdk-aac-dev libflac-dev libmad0-dev libmp3lame-dev libogg-dev \
-    libopus-dev libpcre3-dev libtag1-dev libsamplerate0-dev
+    libopus-dev libpcre3-dev libtag1-dev libsamplerate0-dev libavcodec-dev libavfilter-dev \
+    libavformat-dev libavresample-dev libavutil-dev libpostproc-dev libswresample-dev