# A Novel Consistent Quality Driven for JEM Based Distributed Video Coding
## 3 Proposed JEM Based DVC (JEM-DVC)
### Proposed Consistent Quality Driven (CQD) for JEM-DVC
Therefore, in the case of JEM-DVC codec, a new set of quantization values for the JEM based key frame coding also need to be determined for \(QP_{i}\), so that \(QP_{i}\) can adapt to the advanced coding tools that are provided in JEM. This is because JEM Intra coding is the most up to date coding scheme and it has not been employed for any DVC architecture before. Thus, several experiments have been performed on a lot of test video sequences to empirically define the appropriate set of quantization values that \(QP_{i}\) can be assigned to in the proposed KF-Q method. These test video sequences are chosen in the media collection [26], which contain different kinds of motions and texture activities, and encoded while using a different values setup for QP. Table 1 shows the most appropriate QP  
Figure 5: Inconsistent image quality introduced by DISCOVER DVC for the _Foreman_ sequence: (**a**) \(\mathbf{14}^{th}\) decoded key frame, (**b**) \(\mathbf{14}^{th}\) decoded WZ frame, (**c**) \(\mathbf{15}^{th}\) decoded key frame, (**d**) \(\mathbf{15}^{th}\) decoded WZ frame. The bottom row shows the distortion images between the decoded frames and the original frames, respectively: (**e**) \(\mathbf{14}^{th}\) key frame, (**f**) \(\mathbf{14}^{th}\) WZ frame, (**g**) \(\mathbf{15}^{th}\) key frame, and and (**h**) \(\mathbf{15}^{th}\) WZ frame. values that were obtained from our experiments. These values can be referred to as the reference values, \(QP_{ref}\), setup for \(QP_{i}\) to encode the key frame \(K_{i}\) in the JEM Intra coding scheme of the proposed JEM-DVC. It is confirmed from our experimental results that, when \(QP_{i}\) is assigned by \(QP_{ref}\), \(\left(QP_{i}=QP_{ref}\right)\), the performance of the JEM-DVC codec is not only significantly improved for the key frame encoding, but it can also provide almost smooth video quality for the full set of key and WZ frames. That means that the quality fluctuation between the decoded key and WZ frames in this case can be effectively reduced for the proposed JEM-DVC codec. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \(Q_{1}\) & \(Q_{2}\) & \(Q_{3}\) & \(Q_{4}\) & \(Q_{5}\) & \(Q_{6}\) & \(Q_{7}\) & \(Q_{8}\) \\ \hline _Hall Monitor_ & 38 & 36 & 36 & 33 & 33 & 31 & 29 & 24 \\ _Coastguard_ & 39 & 37 & 37 & 34 & 33 & 31 & 30 & 26 \\ _Foreman_ & 42 & 40 & 38 & 34 & 34 & 32 & 29 & 25 \\ _Soccer_ & 44 & 43 & 40 & 36 & 36 & 34 & 31 & 25 \\ \hline \hline
0 & 0 & 0 & 0 & 0 & 0 & 0 & 4 & 0 & 0 & 0 \\ \hline
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ \hline \end{tabular}
\end{table} 
Table 1: Reference quantization parameters (QPs) applied for the key frame coding in the JEM-DVC codec. Figure 6: Fixed set of eight quantization matrices (QMs). the QM matrix that was determined by the traditional approaches is generally not suitable for reducing the quality fluctuation problem. The reason lies in the fact that, when compared to the traditional DVC codecs based on H.263+ or H.264/AVC [10], the PSNR performance of the decoded key frame in the JEM-DVC codec is much higher and, thus, much different than that of the decoded WZ frames. Therefore, unlike the traditional approaches, in our proposed WZF-Q method, the high performance of PSNRs that was achieved for the key frame coding in JEM-DVC is frequently measured and updated to encode the WZ frames. Specifically, according to each PSNR evaluated for the key frame \(K_{i}\), \(P(K_{i}\), \(QP_{i})\), the PSNRs evaluated for the WZ frame \(WZ_{j}\), \(P\Big{(}WZ_{j},\ QM_{j}\Big{)}\), are also measured and frequently updated for \(WZ_{j}\) with all the candidates of \(QM_{j}\), \(QM_{j}=\ QM_{ref}\ (ref=1,\ 2,\dots,\ 8)\). Among different \(QM_{j}\) candidates defined for \(WZ_{j}\) coding, we choose the optimal \(QM_{opt}\) that can provide not only high coding efficiency for the WZ frame coding, but also minimize the quality fluctuation between the key and WZ frames.