In this thesis, we propose
an audio watermarking system based on wavelet packet decomposition
and psycho-acoustic modeling. The audio watermarking system can deliver
perceptual transparent audio quality, and it is robust against various
signal processing or malicious attacks.
The original audio signal is first segmented and divided into 29 subbands
via wavelet packet decomposition. The bandwidth allocation of the
subband decomposition structure is close to the critical band structure
of human auditory system. Middle and middle-low subbands are chosen
for watermark embedding. A selective embedding method is used to embed
watermark into those coefficient blocks with clear block polarities.
Modification of selected coefficients is based on the minimum masking
threshold of psycho-acoustic model. Instead of the original Audio
signal, a secure key is used in the watermark extraction to indicate
the locations where watermark bits are embedded. In addition, a synchronization
mechanism is imposed to search for the frame boundary of attacked
audio signal.
Simulation results show that the watermarking system is robust against
MP3 compression at 48 Kbps and above. It also survives StirMark attacks
for audio and cropping attacks.