This work presents a novel rate control scheme that suppresses the need for a feedback channel in hash-based distributed
video coding (DVC) architectures. Our state-of-the-art DVC schemes generate side-information (SI) at the decoder by
means of hash-based overlapped block motion estimation followed by probabilistic motion compensation, where key
frames or previously decoded non-key frames, called Wyner-Ziv frames, are used as references.
These DVC systems employ powerful low-density parity-check accumulate codes to code the Wyner-Ziv frames in the
transform domain. Our previous DVC architectures use a classical decoder-driven rate control scheme with a feedback
channel. Specifically, chunks of accumulated syndrome bits are sent from the encoder to the decoder upon request from
the latter until successful decoding is achieved. In order to suppress the feedback channel, the encoder of the DVC
system, proposed in this work, approximates the SI available to the decoder using a novel low complexity SI generation
technique. Subsequently, the conditional probabilities of the original Wyner-Ziv frames, given the approximation of the
SI at the encoder, are used to generate an estimate of the required rate for channel decoding. Hence the presence of a
feedback channel is evaded. Additionally, the proposed feedback channel-free DVC system is equipped with advanced
reconstruction techniques to reduce the impact of failed channel decoding. In this context, our DVC architecture features
iterative refinement of the SI at the decoder. The latter allows for reattempting to decode Wyner-Ziv data for which the
channel decoding failed in previous decoding steps when only a lower quality version of the SI was available.
Experimental results show competitive compression performance of our novel feedback channel-free hash-based DVC
system with respect to the feedback channel-based benchmark in DVC.
This paper analyzes the statistical dependencies between wavelet coefficients in wavelet-based decompositions of 3D meshes. These dependencies are estimated using the interband, intraband and composite mutual information. For images, the literature shows that the composite and the intraband mutual information are approximat-ely equal, and they are both significantly larger than the interband mutual information. This indicates that intraband coding designs should be favored over the interband zerotree-based coding approaches, in order to better capture the residual dependencies
between wavelet coefficients. This motivates the design of intraband wavelet-based image coding schemes, such as quadtree-limited (QT-L) coding, or the state-of-the-art JPEG-2000 scalable image coding standard. In this paper, we empirically investigate whether these findings hold in case of meshes as well. The mutual information estimation results show that, although the intraband mutual information is significantly larger than the interband mutual information, the composite case cannot be discarded, as the composite mutual information is also significantly larger than the intraband
mutual information. One concludes that intraband and composite codec designs should be favored over the traditional interband
zerotree-based coding approaches commonly followed in scalable coding of meshes.