The H.264 Advanced Video Coding (H.264/AVC) standard is considered to be the most commonly used format for video compression. Although it supports a very broad applications range covering all forms of digital compressed video, the confidentiality of the encoded content needs enhancements. The present work proposes a new selective encryption scheme with multiple security levels. In fact, depending on the encrypted coefficients nature, five different cryptographic scenarios are proposed. They provide an effective confidentiality and deal with the real-time processing requirements. The Hardware/Software co-simulation and the experimental results proved the efficiency of the proposed crypto-system that will be suitable for real-time video applications and resource-limited systems.