Energy reduction in video systems: the GreenVideo project

With the current progress in microelectronics and the constant increase of network bandwidth, video applications are becoming ubiquitous and spread especially in the context of mobility. In 2019, 80% of the worldwide Internet traffic will be video. Nevertheless, optimizing the energy consumption for video processing is still a challenge due to the large amount of processed data. This talk will concentrate on the energy optimization of video codecs. In the first part, the Green Metadata initiative will be presented. In November 2014, MPEG released a new standard, named Green Metadata that fosters energy-efficient media on consumer devices. This standard specifies metadata to be transmitted between encoder and decoder for reducing power consumption during encoding, decoding and display. The different metadata considered in the standard will be presented. More specifically, the Green Adaptive Streaming proposition will be detailed. In the second part, the energy optimization of an HEVC decoder implemented on a modern MP-SoC will be presented. The different techniques used to implement efficiently an HEVC decoder on a general-purpose processor (GPP) will be detailed. Different levels of parallelism have been exploited to increase and exploit slack time. A sophisticated DVFS mechanism has been developed to handle the variability of the decoding process for each frame. To get further energy gains, the concept of approximate computing is exploited to propose a modified HEVC decoder capable of tuning its energy gains while managing the decoding quality versus energy trade-off. The work detailed in this second part of the talk is the result of the french GreenVideo FUI project.