Side-Information-Dependent Correlation Channel Estimation in Hash-Based Distributed Video Coding

Abstract

In the context of low-cost video encoding, distributed video coding (DVC) has recently emerged as a potential candidate for uplink-oriented applications. This paper builds on a concept of correlation channel (CC) modeling, which expresses the correlation noise as being statistically dependent on the side information (SI). Compared with classical side-information-independent (SII) noise modeling adopted in current DVC solutions, it is theoretically proven that side-information-dependent (SID) modeling improves the Wyner-Ziv coding performance. Anchored in this finding, this paper proposes a novel algorithm for online estimation of the SID CC parameters based on already decoded information. The proposed algorithm enables bit-plane-by-bit-plane successive refinement of the channel estimation leading to progressively improved accuracy. Additionally, the proposed algorithm is included in a novel DVC architecture that employs a competitive hash-based motion estimation technique to generate high-quality SI at the decoder. Experimental results corroborate our theoretical gains and validate the accuracy of the channel estimation algorithm. The performance assessment of the proposed architecture shows remarkable and consistent coding gains over a germane group of state-of-the-art distributed and standard video codecs, even under strenuous conditions, i.e., large groups of pictures and highly irregular motion content.

Encoder-driven rate control and mode decision for distributed video coding

“…The pursued approach varies from existing schemes by relying on a SI-dependent (SID) correlation channel [11,32] to capture the dependency between the coarse SI and the WZ frame. To limit the likelihood that bit-planes fail to decode due to SW rate underestimation, the final SW rate is adjusted using a novel formula that takes the significance of the bit-plane into account.…”

“…The resulting quantization indices are grouped per band and organized into bit-planes, ready for SW coding based on LDPCA [38] codes. Additionally, the encoder creates a hash frame for every WZ frame, according to the technique presented in [11,34] to enable hash-based SI generation at the decoder.…”

“…High downscaling factors ξ reduce the motion estimation complexity at the cost of reduced accuracy. Next, mimicking the SI generation process at the decoder [11,34], the encoder divides every downscaled WZ frame into overlapping blocks β of B×B pixels with an overlap step size of ε pixels, 1 ≤ ε < B.…”

“…Similar to the noise model established by the decoder, the SID correlation channel concept [11] is adopted. Specifically, the channel output X is modelled by a Laplacian distribution centred on the particular realization of the SI ỹ with a standard-deviation σ(ỹ) that depends on ỹ.…”

“…This paper introduces a novel feedback-channel-free transform-domain WZ (TDWZ) video coding architecture a . The core system is an efficient hash-based WZ video codec [11]. To avoid feedback, the proposed system creates an encoder-side approximation of the SI using a novel technique that mimics the SI generation executed by the decoder, without undermining lowcomplexity encoding.…”