This work presents the design and implementation of hardware based digital watermarking solutions that can insert invisible and semi-fragile watermark into multimedia contents (image or video) captured by CMOS based image sensors, in real time for authentication purposes. The systems are designed to be integrated with the CMOS based camera unit. Starting from our initial JPEG based watermarking design, through an MJPEG one, we will also report on the watermarking solution for the commonly used MPEG encoded video. The current reported system works in real time right after the capturing of video by the CMOS based image sensor. The watermark embedding is processed in the Discrete Cosine Transform (DCT) domain which allows the integration of both watermarking and encoding of the video (or image) into a single system. The hardware based watermarking system described here, works efficiently without high penalty in system power consumption and hardware resources. Moreover, the watermarking rate (watermark generation and embedding) is also high enough to adapt with the frame rate of MPEG-4 video streams in realtime. This new hardware based watermarking system for CMOS based image sensor features minimum video quality degradation and it can withstand certain potential attacks i.e. cover-up attack, cropping, and segment removal from video sequences.