+ boost::signals2::signal<void (ContentVideo)> Video;
+ boost::signals2::signal<void (AudioStreamPtr, ContentAudio)> Audio;
+ boost::signals2::signal<void (boost::weak_ptr<const TextContent>, ContentBitmapText)> BitmapTextStart;
+ boost::signals2::signal<void (boost::weak_ptr<const TextContent>, ContentStringText)> PlainTextStart;
+ boost::signals2::signal<void (boost::weak_ptr<const TextContent>, dcpomatic::ContentTime)> TextStop;
+ boost::signals2::signal<void (ContentAtmos)> Atmos;
+