52.0.2 on ubuntu 16.04 has been built without that Rust mp4 demuxer enabled

[Phil Driscoll]

Absence of the Rust mp4 demuxer (which is present on the official Mozilla build) means that streams containing flac audio data cannot be accessed. This is of particular importance to me and others, as the BBC have started to stream a lossless version of the live Radio 3.

lsb_release -rd
Description: Ubuntu 16.04.2 LTS
Release: 16.04

apt-cache policy firefox
firefox:
  Installed: 52.0.2+build1-0ubuntu0.16.04.1
  Candidate: 52.0.2+build1-0ubuntu0.16.04.1
  Version table:
 *** 52.0.2+build1-0ubuntu0.16.04.1 500
        500 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
        100 /var/lib/dpkg/status
     45.0.2+build1-0ubuntu1 500
        500 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Tom Rank (tom-literaryconnections)]

I discovered this problem when trying to use the new BBC Concert Sound Taster. Their page says:

http://www.bbc.co.uk/taster/projects/radio-3-concert-sound

"We have noticed that Firefox binaries distributed by some flavours of Linux are missing a compilation flag required to enable playback of our FLAC stream. If you are having no luck getting the stream to play on your chosen platform, please try downloading an official Mozilla build which we have verified works correctly. More information is available in this Bugzilla ticket: https://bugzilla.mozilla.org/show_bug.cgi?id=1336057 "

Also using 52.0.2 (64-bit) on Linux Mint (based on Ubuntu 16.04)