In this paper we propose a new approach to protect video sequences while using selective encryption (SE) and reducing the encryption ration (ER). Several methods of SE have been applied to video codec H.264/AVC in CAVLC mode. In our scheme, SE-CAVLC is used but ER is decreased while the confidentiality of the videos is preserved. A selection of macro blocks to encrypt is done using an analysis of the impact of encrypting a single macro block.