# Fast Thumbnail Extraction for H.264/AVC, HEVC and VP9
## 3 Experimental Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sequence Name**} & \multirow{2}{*}{**Original (ms)**} & \multirow{2}{*}{**Proposed (ms)**} & \multirow{2}{*}{**TS**} \\ \hline Campfire & 256 & 88 & 66\% \\ FoodMarket4 & 191 & 69 & 64\% \\ Tango2 & 209 & 72 & 66\% \\ CatRobot & 238 & 84 & 65\% \\ DaylightRoad2 & 234 & 84 & 64\% \\ ParkRunning3 & 319 & 103 & 68\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of the extraction times for H.264/AVC bitstreams. TS: time saving. Figures 9-11 show the thumbnails from the proposed method alongside those from the conventional method, which performs down-sampling after decoding, for the 'Tango2', 'Campfire' and 'ParkRunning3' sequences. They were 4K sequences of 3840 \(\times\) 2160 size. Figures 9-11 show the thumbnails extracted by the proposed algorithm and exiting software, respectively. The width and height of the thumbnails were 1/8 of the original ones, respectively. Since the intra prediction was performed with the reconstructed pixels of the upper and left neighboring boundaries, errors at the boundary pixels propagated to the consecutive blocks. In the worst case, the error could propagate up to the last coding block of the slice or picture. The proposed algorithm was designed to reconstruct the boundary pixels with the same inverse transforms and prediction. The reconstructed pixels were efficiently stored in the down-sampled reference buffers. In addition, the thumbnail was a low-resolution image, the degradation of the image quality in the proposed method was insignificant and it was difficult to see their visual difference. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sequence Name** & **Original (ms)** & **Proposed (ms)** & **TS** \\ \hline Campfire & 178 & 94 & 47\% \\ FoodMarket4 & 159 & 75 & 53\% \\ Tango2 & 156 & 66 & 51\% \\ CatRobot & 178 & 84 & 53\% \\ DaylightRoad2 & 184 & 88 & 58\% \\ ParkRunning3 & 247 & 122 & 52\% \\ \hline \multicolumn{3}{c}{Average} & \multicolumn{2}{c}{52\%} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of the extraction times for HEVC bitstreams. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sequence Name** & **Original (ms)** & **Proposed (ms)** & **TS** \\ \hline Campfire & 300 & 175 & 42\% \\ FoodMarket4 & 259 & 116 & 45\% \\ Tango2 & 256 & 141 & 54\% \\ CatRobot & 297 & 163 & 55\% \\ DaylightRoad2 & 344 & 178 & 45\% \\ ParkRunning3 & 444 & 206 & 48\% \\ \hline \multicolumn{3}{c}{Average} & \multicolumn{2}{c}{48\%} \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison of the extraction times for VP9 bitstreams. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sequence Name** & **H.264** & **HEVC** & **VP9** \\ \hline Campfire & 24.02 & 25.05 & 24.07 \\ FoodMarket4 & 31.48 & 31.84 & 31.13 \\ Tango2 & 28.17 & 28.62 & 28.07 \\ CatRobot & 23.74 & 24.37 & 23.93 \\ DaylightRoad2 & 25.26 & 25.70 & 25.29 \\ ParkRunning3 & 21.82 & 22.53 & 22.49 \\ \hline Average & 25.75 & 26.35 & 25.83 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: PSNR (dB) compared with the conventional method for each codec. Figure 10: Subjective quality performance for the ‘Campfire’ sequence. Figure 9: Subjective quality performance for the ‘Tango2’ sequence.