We propose an algorithm to embed data directly in the bitstream of JPEG imagery. The motivation for this approach is that images are seldom available in uncompressed form. Algorithms that operate in spatial domain, or even in coefficient domain, require full (or at best) partial decompression. Our approach exploits the fact that only a fraction of JPEG code space is actually used by available encoders. Data embedding is performed by mapping a used variable length code (VLC) to an unused VLC. However, standard viewers unaware of the change will not properly display the image. We address this problem by a novel error concealment technique. Concealment works by remapping run/size values of marked VLCs so that standard viewers do not lose synchronization and displays the image with minimum loss of quality. It is possible for the embedded image to be visually identical to the original even though the two files are bitwise different. The algorithm is fast and transparent and embedding is reversible and file-size preserving. Under certain circumstances, file size may actually decrease despite carrying a payload.

In this work we propose a new algorithm for fragile, high capacity yet file-size preserving watermarking of MPEG-2 streams. Watermarking is done entirely in the compressed domain, with no need for full or even partial decompression. The algorithm is based on a previously developed concept of VLC mapping for compressed domain watermarking. The entropy-coded segment of the video is first parsed out and then analyzed in pairs. It is recognized that there are VLC pairs that never appear together in any intra-coded block. The list of unused pairs is systematically generated by the intersection of "pair trees." One of the trees is generated from the main VLC table given in ISO/IEC 13818-2:2000 standard. The other trees are dynamically generated for each intra coded blocks. Forcing one VLC pairs in a block to one of the unused ones generates a watermark block. The change is done while maintaining run/level change to a minimum. At the decoder, the main pair tree is created offline using publicly available VLC tables. Through a secure key exchange, the indices to unused code pairs are communicated to the receiver. We show that the watermarked video is reasonably resistant to forgery attacks and remains secure to watermark detection attempts.

In this work we present an application of video digital watermarking to metadata embedding in UAV video footage. Digital watermarking provides the capability of embedding invisible signatures in digital media. As digital media is easily transported, copied or exchanged, a marked file provides innumerable advantages for tracking, fingerprinting, ownership verification and possibly covert communication. UAVs collect voluminous amount of metadata along with surveillance footage. Presently, metadata stream is transmitted on a separate channel or stored in the header section of video. The former approach occupies bandwidth whereas the latter approach leaves metadata in the open and easily removable. We have adapted our recently developed MPEG-2 watermarking algorithm to embed flight metadata directly in MPEG bitstream of UAV video. By intertwining metadata with video, the two streams cannot be easily separated, bookkeeping is reduced and security is enhanced. These goals are achieved at little or no cost. Video quality is maintained and file size is not increased. The algorithm is applied to Predator video footage.

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