void audio (boost::weak_ptr<Piece>, AudioStreamPtr, ContentAudio);
void image_subtitle (boost::weak_ptr<Piece>, ContentImageSubtitle);
void text_subtitle (boost::weak_ptr<Piece>, ContentTextSubtitle);
void audio (boost::weak_ptr<Piece>, AudioStreamPtr, ContentAudio);
void image_subtitle (boost::weak_ptr<Piece>, ContentImageSubtitle);
void text_subtitle (boost::weak_ptr<Piece>, ContentTextSubtitle);