Most of quantization based data hiding schemes are based on uniform scalar quantizer, which is optimal only if the host signal is uniformly distributed. In our recent work, we proposed two pdf-matched quantizer based data hiding schemes, both of which have better embedding efficiency than conventional uniform quantizer based schemes. But these schemes require a lot of location information for qualified pixels, which increases the side information needed by the decoder. Moreover, these schemes are inconvenient when high embedding rates are desired. In this paper, we propose a trellis coded quantizer (TCQ) based data hiding scheme, which is proved to be more embedding efficient than traditional quantizer based schemes. Experimental results show that the
proposed scheme can be up to 1.2 dB closer to the capacity upper bound than the QIM scheme over the whole watermark noise rate (WNR) range. Comparing with our previous work, the proposed TCQ based scheme has less side information and can easily realize a high embedding rate.
Today, data hiding has become more and more important in a variety of applications including security. Since
Costa's work in the context of communication, the set of quantization based schemes have been proposed as one
class of data hiding schemes. Most of these schemes are based on uniform scalar quantizer, which is optimal
only if the host signal is uniformly distributed. In this paper, we propose pdf -matched embedding schemes,
which not only consider pdf -matched quantizers, but also extend them to multiple dimensions. Specifically,
our contributions to this paper are: We propose a pdf-matched embedding (PME) scheme by generalizing the
probability distribution of host image and then constructing a pdf-matched quantizer as the starting point.
We show experimentally that the proposed pdf-matched quantizer provides better trade-offs between distortion
caused by embedding, the robustness to attacks and the embedding capacity. We extend our algorithm to embed
a vector of bits in a host signal vector. We show by experiments that our scheme can be closer to the data
hiding capacity by embedding larger dimension bit vectors in larger dimension VQs. Two enhancements have
been proposed to our method: by vector flipping and by using distortion compensation (DC-PME), that serve
to further decrease the embedding distortion. For the 1-D case, the PME scheme shows a 1 dB improvement
over the QIM method in a robustness-distortion sense, while DC-PME is 1 dB better than DC-QIM and the 4-D
vector quantizer based PME scheme performs about 3 dB better than the 1-D PME.