Multiple Watermarking and Capacity Analysis of Digital Image

According to the multiple accessing technique of Code Division Multiple Access (CDMA) system, multiple watermarks are encoded with convolution and interleaved in block. Orthogonal Gold sequences are used to spread spectrum of the copyright messages. CDMA encoded copyright messages are embedded into the wavelet sub-bands except HH1 sub-band. The embedded amplitude is decided by Watson's perceptual model of wavelet transform domain, and the embedded position in the selected wavelet sub-bands is decided randomly by a Pseudorandom Noise (PN) sequence. Watermarks are extracted without the need of original image. The capacity of proposed algorithm is also discussed. Experimental results show that proposed algorithm improves the detection Bits Error Rate (BER) and that multiple watermarks have preferable robustness and invisibility.