# Load Balancing Strategies for Slice-Based Parallel Versions of JEM Video Encoder
## 3 Parallel Approaches
### Asynchronous Algorithm: JEM-SP-ASync
Tables 14 and 15 show the parallel efficiency and the computational times obtained by the JEM-SP-ASync algorithm for all video sequences tested here. The results confirm that the automatic load balancing process implemented in the JEM-SP-ASync algorithm works correctly and shows very good scalability, especially compared to the JEM-SP-sync algorithm (Table 12). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Parallel Efficiency**} \\ \hline Video & & QP & QP & QP & QP \\ sequence & NoT & 22 & 27 & 32 & 37 \\ \hline \multirow{4}{*}{BQSQ} & 2 & 93.1\% & 96.1\% & 95.0\% & 96.7\% \\  & 3 & 93.7\% & 92.6\% & 94.6\% & 95.2\% \\  & 4 & 92.7\% & 92.7\% & 94.8\% & 95.7\% \\  & 8 & 86.2\% & 88.3\% & 88.8\% & 88.9\% \\ \hline \multirow{4}{*}{PART} & 2 & 98.3\% & 98.6\% & 99.4\% & 99.0\% \\  & 3 & 95.3\% & 96.3\% & 97.1\% & 97.9\% \\  & 4 & 94.4\% & 95.1\% & 96.7\% & 96.4\% \\  & 5 & 93.3\% & 95.2\% & 94.6\% & 93.2\% \\  & 6 & 92.6\% & 93.4\% & 93.0\% & 92.2\% \\  & 7 & 92.0\% & 91.2\% & 94.2\% & 93.3\% \\  & 8 & 91.3\% & 91.3\% & 92.1\% & 92.5\% \\  & 10 & 91.9\% & 90.0\% & 93.7\% & 90.8\% \\ \hline \multirow{4}{*}{FOUR} & 2 & 97.9\% & 98.9\% & 97.2\% & 98.8\% \\  & 3 & 95.2\% & 94.5\% & 94.3\% & 95.2\% \\  & 4 & 95.0\% & 92.3\% & 94.1\% & 94.9\% \\  & 5 & 97.8\% & 93.9\% & 94.7\% & 94.6\% \\  & 6 & 93.9\% & 93.1\% & 92.7\% & 91.6\% \\  & 7 & 95.3\% & 93.8\% & 93.3\% & 93.5\% \\  & 8 & 94.1\% & 92.2\% & 92.6\% & 91.0\% \\  & 9 & 95.0\% & 93.8\% & 92.9\% & 93.0\% \\  & 10 & 92.6\% & 91.2\% & 91.8\% & 90.0\% \\  & 12 & 89.9\% & 89.5\% & 87.6\% & 88.4\% \\ \hline \multirow{4}{*}{PARK} & 2 & 98.5\% & 98.2\% & 97.4\% & 98.1\% \\  & 3 & 95.4\% & 95.1\% & 93.1\% & 94.7\% \\  & 4 & 94.0\% & 94.2\% & 90.5\% & 94.6\% \\  & 5 & 94.2\% & 95.7\% & 92.9\% & 93.1\% \\  & 6 & 94.7\% & 93.6\% & 89.9\% & 93.4\% \\  & 7 & 93.6\% & 91.2\% & 93.2\% & 94.2\% \\  & 8 & 93.7\% & 93.4\% & 91.8\% & 92.7\% \\  & 9 & 94.2\% & 92.6\% & 91.2\% & 92.9\% \\  & 10 & 93.3\% & 92.4\% & 91.8\% & 89.1\% \\  & 11 & 92.4\% & 92.2\% & 87.9\% & 89.9\% \\  & 12 & 89.5\% & 89.4\% & 88.5\% & 88.5\% \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Parallel efficiency for Algorithm JEM-SP-ASync. It should be noted that in order to develop both algorithms, several procedures of the reference software had to be modified. The number of modified processes is greater in JEM-SP-ASync than in JEM-SP-Sync. However, none of these changes affect the encoding processes implemented in the reference software. Obviously, in the reference software, the encoded slices are totally independent, which is necessary in order to develop parallel algorithms without modifying the standard encoding process. We detected that slice encoding depends on the order in which it is encoded. That is, when the slices are independently encoded in a disordered way, there is a small change in the reference software. In any case, regardless of the order of encoding of the slices, the slices are totally independent. Tables 16 and 17 show the bit rate and PSNR values for the sequential and parallel algorithms, respectively. As can be seen, the differences between the two types of algorithm are almost negligible, although the bit rate is slightly lower and the PSNR slightly better in the parallel algorithm. This is because in the reference software, the initial values of some of the variables that slightly modify the intra-prediction procedure vary