Abstract: The invention proposes a method of filtering a bitstream according to user specifications. The proposed method uses a semantic description and a syntactical description of the bitstream. The semantic description is scanned to select the elementary units that match the user specification. The time is used as a linking mechanism between the semantic description and the syntactical description to locate the elements of the syntactical description that are to be removed. A filtered syntactical description is generated by removing the located elements. Finally, a filtered bitstream is generated from the filtered syntactical description.

Abstract: The invention proposes a method of filtering a bitstream according to user specifications. The proposed method uses a semantic description and a syntactical description of the bitstream. The semantic description is scanned to select the elementary units that match the user specification. The time is used as a linking mechanism between the semantic description and the syntactical description to locate the elements of the syntactical description that are to be removed. A filtered syntactical description is generated by removing the located elements. Finally, a filtered bitstream is generated from the filtered syntactical description.

Abstract: The invention proposes an interactive a system comprising user units (1a, 1b, 1c) intended to display a content broadcast by a content supply unit (3). According to the invention, the user units are designed to transmit user data (Da, Db, Dc) to an application control unit (2). The application control unit determines pieces of content to be overlaid from user data received. It transmits overlay data to the user units and/or to the content supply unit. These overlay data are used by the user units and/or by the content supply unit for overlaying the pieces of content determined by the application control unit in the content to be displayed and/or in the content to be broadcast. Application: interactive television.