A DWT-based Digital Video Watermarking Scheme with Error Cor(3)

Abstract. In this paper, a digital video watermarking algorithm is proposed. We present a novel DWT-based blind digital video watermarking scheme with scrambled watermark and error correcting code. Our scheme embeds different parts of a single watermark in

independent watermarks to each frame also presents a problem: Regions in each video frame with little or no motion remain the same frame after frame. These motionless regions may be statistically compared or averaged to remove independent watermarks

[8,9], so we use an identical watermark within each motionless scene. With these mechanisms, the proposed method is robust against the attack of frame dropping, averaging, swapping, and statistical analysis. At the same time, error correcting codes are extracted from the watermark and embedded as an audio watermark in the audio channel, which in turn makes it possible to correct and detect the changes from the extracted watermarks. This addition protection mechanism enables the scheme to overcome the corruption of a watermark, thus the robustness of the scheme is increased under certain attacks.

This newly proposed scheme consists of four parts, including: watermark preprocess, video preprocess, watermark embedding, and watermark detection. Details are described in the following sections.

2.1. Watermark Preprocess

Watermark preprocess consists of two parts, video watermark and audio watermark. After both watermarks are preprocessed, they will be embedded into video channel and audio channel, respectively.

Video Watermark. A Watermark is scrambled into small parts in preprocess, and they are embedded into different scenes so that the scheme can resist to a number of attacks specified to the video. A 256-grey-level image is used as a watermark, as shown in Fig. 3a, so 8 bits can represent each pixel. The watermark is first scaled to a particular size with the following equation

p + q = n , p and q > 0 (1)

where m is the number of scene changes and n, p, q are positive integers. And the size

of the watermark should be

(2)

Then the watermark is divided into 2n small images with size 64 × 64. Fig. 2 and 3 show the procedure and the result of watermark preprocess with m = 10, n = 3, p = 1,

and q = 2.

Fig. 2. Overview of watermark preprocess.