# An Upgraded Version of the Binary Search Space-Structured VQ Search Algorithm for AMR-WB Codec
## 4 Experimental Results  
In this work, a performance comparison is conducted among the EEENNS, DI-TIE, ITIE, and the original and upgraded versions of BSS-VQ. Since EEENNS, DI-TIE, and ITIE provide a 100% search accuracy in comparison with the full search approach, there is no degradation in the speech quality. Furthermore, as mentioned in the previous section, a nearly lossless speech quality is provided in both the original and the upgraded versions of BSS-VQ. For this reason, performance is compared in terms of the search load, i.e., the average number of searches. For testing purposes, a speech database, including one male and one female speaker, in total requires more than 221 MB of memory, takes up more than 120 min, and covers 363,281 speech frames as well. Table 3 gives a comparison on the average number of searches among the full search, EEENNS, DI-TIE, and ITIE, while Tables 4 and 5 list the search load versus the \(TQA\) values for the original and the upgraded versions of BSS-VQ, respectively. Furthermore, with the search load required in the full search approach as a benchmark, Table 6 compares the load reduction (LR) among various search algorithms listed in Tables 3-5. Obviously, a high search load reduction is indicated by a high value of LR. Moreover, columns 2 and 3 give LRs in codebooks CB1 and CB2, respectively. The overall LR refers to the total search load, defined as the sum of the average number of searches multiplied by the vector dimension in each codebook, and is employed to compare the total search load required during an entire VQ encoding procedure for an input vector, as presented in the rightmost two columns therein. As can be found in Tables 3-5, the upgraded version of BSS-VQ outperforms its counterparts to a great extent with respect to the search load required in each codebook. Particularly, Table 6 gives a clear view of the LR comparisons. As tabulated therein, the codebook search, required in CB1 and CB2 at stage 1, occupies a high percentage of the search load in an entire VQ encoding procedure. For instance, the full search algorithm requires a search load of 4096 (= 256 \(\times\) 9 + 256 \(\times\) 7) at stage 1, accounting for 77% of a 5280 overall search load, as tabulated in Tables 3 and 6. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**TQA**} & \multicolumn{6}{c}{**Average Number of Searches in Various Codebooks**} \\ \cline{2-7}  & **CB1** & **CB2** & **CB11** & **CB12** & **CB13** & **CB21** & **CB22** \\ \hline
0.90 & 15.40 & 26.45 & 12.47 & 19.96 & 19.93 & 7.11 & 6.66 \\
0.91 & 16.10 & 27.52 & 12.86 & 20.84 & 20.62 & 7.11 & 6.72 \\
0.92 & 16.80 & 28.85 & 12.99 & 21.50 & 21.19 & 7.64 & 6.91 \\
0.93 & 17.79 & 30.23 & 13.52 & 21.84 & 22.02 & 7.64 & 7.15 \\
0.94 & 18.87 & 31.71 & 14.04 & 22.85 & 22.72 & 8.00 & 7.57 \\
0.95 & 20.03 & 33.58 & 14.61 & 23.85 & 23.72 & 8.26 & 7.84 \\
0.96 & 21.36 & 35.81 & 15.04 & 24.76 & 24.95 & 8.87 & 8.21 \\
0.97 & 23.18 & 38.37 & 15.86 & 25.93 & 26.24 & 9.27 & 8.51 \\
0.98 & 25.71 & 41.82 & 16.73 & 27.60 & 27.86 & 10.00 & 9.33 \\
0.99 & 29.71 & 47.12 & 18.21 & 29.61 & 29.99 & 10.49 & 10.15 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Search load versus threshold of quantization accuracy (\(TQA\)) values in the 8.85–23.85 kbps modes for the original version of the binary search space-structured vector quantization (BSS-VQ) algorithm. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Codebooks**} & **Full Search** & **EEENNS** & **DI-TIE** & **ITIE** \\ \hline Stage 1 & CB1 & 256 & 58.82 & 42.46 & 58.01 \\  & CB2 & 256 & 63.87 & 42.79 & 62.03 \\ \hline Stage 2 & CB11 & 64 & 14.17 & 12.31 & 13.10 \\  & CB12 & 128 & 22.91 & 14.40 & 15.32 \\  & CB13 & 128 & 21.01 & 13.50 & 14.40 \\  & CB21 & 32 & 11.08 & 8.95 & 9.48 \\  & CB22 & 32 & 17.44 & 12.42 & 13.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average number of searches among various approaches in the 8.85–23.85 kbps modes.