Performance and energy consumption analysis of the X265 video encoder

The ×265 video encoder aims at improving the speed and the computational efficiency of HEVC encoders implementation. In this paper we present a detailed energy consumption analysis, considering the consumption components of CPU, cache memories and main memory, for all ×265 presets executing in a multicore system. Ten HD 1080p test video sequences with different motion and brightness characteristics are used in the experiments. Three tools are used to obtain the results: CACTI, PCM and Perf. To get more reliable time/energy results, 10 executions were performed for each preset. The results show that fast presets are 47× faster than slower presets. However, slower presets use robust configurations and achieve large reductions in bitrate. Due to this, the ultrafast preset has a bitrate 45% higher than placebo preset. Furthermore, the system energy consumption increases 45×, from ultrafast preset to placebo preset. Our experiments clearly present the dependence between bitrate and energy consumption for all encoding presets, which allows us to choose the best bitrate/energy trade-off for each platform at hand.