In this paper we present a DCT domain watermarking approach for H.264/AVC video coding standard. This scheme is resilient to compressed-domain temporal adaptation. A cryptographic hash function is used to generate a semi-fragile watermark to provide content-based authentication. The embedded watermark can withstand frame-dropping due to temporal adaptation, yet it is able to detect malicious attacks such as content modification, transcoding etc. Simulation results demonstrate that the watermarking scheme is computationally efficient and suitable for practical use.