# A Novel Consistent Quality Driven for JEM Based Distributed Video Coding
## 3 Proposed JEM Based DVC (JEM-DVC)
### JEM Based Key Frame Coding  
As mentioned in Section 1, the key frame coding plays an important role, not only as the most meaningful benchmark of low coding complexity, but also as the essential factor for improving the performance of DVC codecs. Generally, the key frame is encoded while using the Intra coding schemes that were provided by the traditional predictive coding standards, such as H.263, H.264/AVC, or H. 265/HEVC. In [9], the authors et al. showed that the DVC codec utilizing H.265/HEVC for the key frame coding can outperform that utilizing H.264/AVC by up to 2.5-3.0 dB. Therefore, it is expected that the more powerful and effective Intra coding technique applied for key frame coding, the better Rate-distortion performance can be provided for a DVC codec. Figure 2: Proposed Joint exploration model based distributed video coding (JEM-DVC) architecture. Recently, it is worth noticing that the best available video coding standard is no longer H.264/AVC or H.265/HEVC, but rather the FVC standard with JEM [17; 23]. As reported in [24], the main goal of JEM is to explore the future video coding technology with a compression capability that significantly exceeds the current HEVC standard. In [25], [PERSON] et al. has shown that the FVC/JEM codec can provide up to 40% coding efficiency gains for the Intra/Inter coding as compared to the H.265/HEVC. Additionally, for the Intra coding mode only, the gain that can be achieved is about 20%. In this work, we propose a novel JEM based key frame coding scheme, being inspired from the recent achievements of the FVC/JEM research. To the best of our knowledge, this is the most up-to-date compression solution for the key frame coding. In addition, we also adaptively configure JEM Intra coding tools to effectively apply to the proposed JEM-DVC codec to meet the requirement of low encoding complexity. Specifically, in JEM, the number of Intra prediction modes is extended to 67 modes, which include 65 angular modes plus DC and planar modes [16]. All of these prediction modes are available to favor all of the block sizes of the quad tree plus binary tree (QTBT) block structure. QTBT is a novel coding structure block that JEM introduces, which includes coding tree units (CTUs) and each CTU contains smaller coding units (CUs). In JEM software, it is possible to configure a large block size for a CTU (up to \(256\times 256\)). Similar to the prior video coding standards, like H.264/AVC and H.265/HEVC, the principle of defining an optimal Intra prediction mode in JEM is to recursively search to find the optimal coding tree structure. On every possible CTU size, a complex rate distortion optimization (RDO) is performed among all of the 67 prediction candidate modes, in order to screen out the best prediction mode [17]. These lead to a very complicated and time-consuming calculation, especially for such a high number of Intra prediction modes that are provided in JEM, and thus strongly against the low coding complexity that is required for a DVC encoder. In addition, the targets of our proposed JEM-DVC codec are usually the low complexity constrained video applications, e.g., wireless sensor networks, wireless surveillance, or remote sensing systems. Thus, the input videos of these emerging applications tend to have low resolutions with low motion activities. In this context, a large number of Intra prediction modes, as introduced in JEM, may not necessary. Therefore, in this work, many experiments have been performed on several test sequences to empirically define the most suitable prediction modes and CTU sizes to effectively reduce the time that is consumed to find the best prediction mode. From experiments, it is confirmed that, in cases of low resolution applications, we can empirically define the number of Intra prediction modes and the size of CTU setup for all directional prediction modes as \(N_{mode}=35\) and \(CTU_{size}=64\times 64\), respectively. Figure 3 illustrates all of the prediction modes utilized for the proposed JEM based key frame coding in detail.