playing audioble in firefox

[Jan Stary]

Hi all,

is anyone able to play cudible audible.com content in Firefox,
such as https://www.audible.com/webplayer?asin=1398700622 ?
What I get is an error message saying

        Playback is not supported on this browser.
        Please enable playback of DRM protected content.

In Firefox's about:config I see "drm" and "DRM",
both are set to true. I don't see anything related
in the pkg-readme.

        Jan