**2.1 Wyner-Ziv video coding**

The first practical Wyner-Ziv framework was proposed by Stanford in (Aaron et al., 2002), and this work was widely referenced and improved in later proposals. As a result, in (Artigas et al., 2007) an architecture called DISCOVER was proposed which outperforms the previous Stanford one. This architecture provided a reference for the research community and finally it was later improved upon with the VISNET-II architecture (Ascenso et al., 2010), which is depicted in Figure 1. In this architecture, the encoder splits the sequence into two kinds of frames: Key Frames (K) and Wyner-Ziv Frames (WZ) in module (1). K frames are encoded by an H.264/AVC encoder in (2). On the other hand, WZ frames are sent to the WZ encoder, where the information is firstly quantized (3a), and BitPlanes (BPs) are extracted in (3b); in (3c) each BP is independently channel encoded and several parity bits, which are stored in a buffer (3d), are calculated. On the decoder side, initially K frames are decoded by an H.264/AVC decoder (4). From these frames, Side Information (SI) is calculated in (5), which represents an estimation for each non-present original WZ frame. For this estimation, the Correlation Noise Model (CNM) module (6) generates a Laplacian distribution, which models the residual between SI and the original frame. Afterwards, SI and CNM are sent to the turbo decoder, which corrects differences of SI and the original frame by means of iterative decoding (requesting several parity bits from the encoder through the feedback channel). Finally, decoding bitplanes are reconstructed in module (7c).

Fig. 1. Block diagram of the reference WZ architecture [Ascenso et al. 2010].
