Dissertation Defense - Mehmet Necmettin Akçay (PHDCS)

Mehmet Necmettin Akçay – Ph.D. Computer Science

Assoc. Prof. Dr. Ali C. Beğen– Advisor

Date: 11.08.2022

Time: 14:00

Location: AB1 225

“SERVER AND CLIENT-SIDE ALGORITHMS FOR ENHANCING ADAPTIVE STREAMING”

Assoc. Prof. Dr. Ali Cengiz Beğen, Özyeğin University

Prof. Dr. M. Reha Civanlar, Özyeğin University

Asst. Prof. Dr. İsmail Arı, Özyeğin University

Assoc. Prof. Dr. Müge Sayıt, Ege University

Asst. Prof. Dr. Tankut Akgül, Istanbul Technical University

Abstract:

HTTP adaptive video streaming is a technique widely used on the internet today to stream live and on-demand content. Server and client-side algorithms play an important role in achieving a better user experience in terms of metrics such as latency, rebufferings and rendering quality. After explaining commonly used metrics, we analyzed four main aspects of video streaming (i) bandwidth prediction accuracy, (ii) utilization of playback speed, (iii) adaptive streaming for content-aware-encoded (variable encoded) videos and (iv) head motion awareness for 360-degree videos. 360-degree video streaming requires much higher bandwidths compared to 2D streaming. We demonstrated that most of the algorithmic improvements achieved for 2D streaming can also be applied to Viewport Dependent Streaming (VDS) for 360-degree video. It is also important that in 360-degree video streaming, we have a Head Mounted Display (HMD) device that is capable of pointing the viewport orientation of the user. We have also investigated and improved 360-degree ABR algorithms by adding to the improvements accomplished in 2D streaming by developing several new algorithms using the HMD. The new algorithms proposed in this thesis are Low-on-Latency (LoL), Low-on-Latency+ (LoL+), Bang-on-Bandwidth (BoB), Size-aware Rate Adaptation (SARA), Content-aware Playback Speed Control (CAPSC), Head-motion-aware Viewport Margins (HMAVM). We have evaluated the proposed new algorithms using the objective metrics discussed in detail and showed significant contributions for those new algorithms including up to 91% decrease in rebuffering duration for on-demand streaming, 61.9% decrease in rebuffering duration, and 8.1% decrease in latency compared to L2A for low latency streaming, 81.3% bandwidth prediction accuracy for interactive streaming, lastly 20% improvement in viewport quality and 50% reduction in motion to high-quality delay for 360 video streaming.

Bio:

Mehmet N. Akcay received his B.Sc., in the field of Computer Engineering, from Istanbul Technical University in 2005. He completed his M.Sc. in the same field in Bogazici University in 2008 and he has been working in the industry for more than 15 years. His research interests are HTTP adaptive streaming, low-latency live streaming and 360 degree video streaming.