Novel Segment-Based Rate Control Scheme for x265 Open-Source Video Encoder

There is a rapid development in various multimedia services such as mobile streaming services, video conferencing and live video streaming platforms [1],[2]. To achieve a high quality-of-experience (QoE), video streaming platforms require infrastructure updates and call for stable transmission by using the Adaptive Bitrate (ABR) streaming, technique, according to which the stream's bitrate is automatically increased/decreased to deliver a high-quality streaming experience in real-time. The x265 encoder [3],[4] is a popular open-source encoder, which generates bitstreams compliant with the HEVC video coding standard [5]. Built on top of x264 [6], the x265 encoder is integrated into several popular open-source frameworks, such as ffmpeg [7], GStreamer [8], and HandBrake [9]. x265 is used by a variety of broadcast and streaming service providers who leverage the benefits of HEVC for streaming live and over-the-top (OTT) content. In addition to implementing nearly all the tools defined in HEVC, it implements many algorithmic optimizations that enable trading off encoder performance for quality [2]-[4]. This flexible architecture of x265 makes it a popular choice for HEVC encoding for both on-premises and on the cloud services. Recent x265 development efforts have been focused on an additional coding gain increase, while there is a continuous development effort to support the ABR streaming, in which the video is decomposed into small segments of 2 to 10 seconds. Every video segment is encoded at multiple resolutions and bitrates, and then saved in small media files at the web servers or Content Delivery Networks (CDN). As a result, an adaptive playback is a way for video players to dynamically match the video stream quality to network conditions, available bandwidth, as well as to the device processing/memory resources.