ROBUST SPREAD SPECTRUM BASED PATCHWORK AUDIO WATERMARKING

Digital Watermarking refers to hiding digital data in digital content with intent to enable copyright protection and illegal distribution. Digital audio watermarking deals with embedding digital information in an imperceptible manner in the host audio signal. Audio watermarking involves much more complex techniques to embed watermark in view of superiority of Human Auditory System (HAS) over Human Visual System (HVS). Spread Spectrum watermarking embeds the watermark in frequency domain, thereby providing a much more robust and invisible watermarking scheme as compared to time domain watermarking, which is comparatively fragile. It turns out that digital watermark embedding in audio signals in any domain results in audible disturbances in the original audio signal. To compensate for these unwanted disturbances in audio files, audio watermarking techniques are to be augmented with Frequency Masking (FM) techniques. It turns out that PAFM creates an imbalance in the number of positive and negative chips that are used to modulate the watermark, and consequently, it introduces error in correlation test. This paper proposes a robust audio watermarking technique based on the patchwork algorithm. Peak Signal to Noise Ratio (PSNR) is evaluated as a function of embedding capacity and robustness. PAFM is analyzed as a function of the threshold limit for embedding of watermark bits. The proposed method provides an optimized way to embed watermark using spread spectrum technique, with a detector of minimal complexity and maximum achievable efficiency. MABLAB is used to simulate the technique and results are derived. PSNR is used as a quality metric for evaluation of the results.