Watermarking solutions can be broadly classified into A/B watermarking and bitstream-based watermarking. Since A/B watermarking techniques require huge storage space for managing different segments of content as well as involve significant preparation and delivery costs, content providers are becoming increasingly inclined towards bitstream-based watermarking solutions, which are free from the aforementioned limitations. In addition, they are also more suitable for live content streaming, whereas A/B watermarking might lead to latency and complexities in identifying the source of leakage.
In the bitstream-based video watermarking, the watermark is embedded in real time directly in the bitstream domain without complete decompression and re-encoding of the signal. During the embedding process, the frames of the video file are profiled to identify candidate blocks and then manipulated without compromising the video quality. The information about which candidate blocks are manipulated and how they are altered is stored in a separate metadata file and sent along with the content copy. Since the content file is still stored and distributed by the CDN, while the watermarking insertion is carried out during the adaptive bitrate streaming, each viewer receives a uniquely watermarked version of the content copy. This technique is also faster in comparison to A/B video watermarking as insertion is carried out at the rate of several bits per second. In addition, it also makes it difficult to mask the watermark after it has been inserted, thereby reducing piracy attempts.
Since bitstream watermarking takes place after the encoding step, a better sound quality can be achieved in the video as the quality loss by repeated encoding/decoding of audio material (“cascaded coding”, “tandem coding”, etc.) is avoided.
Furthermore, since bitstream-based solutions implement a shortcut operation within the coded domain itself, they are more suitable for real-time on-the-fly watermarking. The content does not even require any further encoding step as the result of bitstream watermarking is already in a compressed form and can be easily distributed. Content databases today are consequently based on compressed data formats. Thus, bitstream watermarking is fast emerging as the most preferred method to prevent piracy of OTT and VoD DRM protected content. It is a robust, practical, cost-effective, and scalable solution which is also compatible with different platforms and delivery protocols.
