02-11-2012, 06:02 PM
Effective Pseudonoise Sequence and Decoding Function for Imperceptibility and Robustness Enhancement in Time-Spread Echo-Based
Audio Watermarking
Effective Pseudonoise Sequence.pdf (Size: 684.13 KB / Downloads: 20)
INTRODUCTION
RECENT advances in communication networks, computers
and multimedia technology facilitate the efficient
distribution, reproduction, and manipulation of digital media,
without any quality degradation. This has yielded strong demand
for the protection of digital media concerning intellectual
property rights. For example, the music industry loses millions
of dollars every year due to unauthorized copying and distribution
of music and other sound signals. Digital watermarking is
a promising technique to tackle this problem [1]–[7].
Imperceptibility
The imperceptibility of the new watermarking method
is investigated using both listening test and quantitative
measurement.
1) Listening Test: Imperceptibility is a subjective index associated
with human perceptual features. It can be measured by
listening test. The listening test was carried out using the listening
test approach shown in [1]. Two audio signals were employed
as host signals. Five male subjects and two female subjects
aged between 20 and 30 years with normal hearing participated
in the listening test. The AXB paradigm was used to
examine the difference of sound quality between a host signal
and a watermarked signal. A and B can be a host signal or a watermarked
signal, but they are always different from each other.
X was randomly set to either A or B. The subjects were asked
to judge which of A or B was the same as X. Clearly, the lower
imperceptibility the watermarked signal has, the higher possibility
correct judgement can be made. Since the chance level is
50%, the amplitude of PN sequence, , that gives a correct response
rate of 75% is defined as the discrimination threshold.
Beyond this value, the subjects are considered to be able to distinguish
the sound quality between a host signal and a watermarked
signal.
CONCLUSION
In this paper, we propose an effective PN sequence for timespread
echo-based audio watermarking. The proposed sequence
yields an echo kernel whose magnitude response has smaller
magnitudes in the perceptually significant region. Furthermore,
its correlation function has more large peaks than that of the existing
PN sequence, from which a modified decoding function
is derived. As a result, the new audio watermarking method that
jointly employs the proposed PN sequence and decoding function
can significantly enhance the perceptual quality of the watermarked
signal and the robustness of time-spread echo-based
audio watermarking. The superior performance of our method is
demonstrated by simulation examples and listening test, in comparison
with the audio watermarking methods in [1] and [3].