void emit_video (boost::weak_ptr<Piece>, boost::shared_ptr<DecodedVideo>);
void emit_audio (boost::weak_ptr<Piece>, boost::shared_ptr<DecodedAudio>);
void emit_video (boost::weak_ptr<Piece>, boost::shared_ptr<DecodedVideo>);
void emit_audio (boost::weak_ptr<Piece>, boost::shared_ptr<DecodedAudio>);