Robustness improvement in spread spectrum watermarking using M-ary modulation (original) (raw)

Spread spectrum (SS) modulation principle is widely used in digital watermarking to satisfy the robustness criterion against various common signal processing operations as well as deliberate external attacks. Several SS image watermarking schemes have been developed in various transform domains such as DCT (discrete cosine transform), DHT (discrete Hadamard transform), Fourier-Mellin, and Wavelet etc using binary signaling. The use of wide spectrum of the cover data in message hiding process puts a limit on data rate subject to a given embedding distortion. The paper investigates the scope of using M-ary modulation principle for performance improvement over binary signaling scheme. The current work also suggests data embedding in selected sub bands using DWT (discrete wavelet transform) and MbDWT (M-band wavelet transform) decomposition. Performance improvement of Mary signaling principle in SS scheme and superiority of wavelet domain embedding over spatial domain approach are also supported by numerical results against JPEG and JPEG 2000 compression operations.