I. Sodagar

Bio: I. Sodagar is an academic researcher from Microsoft. The author has contributed to research in topics: The Internet & Set (abstract data type). The author has an hindex of 1, co-authored 1 publications receiving 958 citations.

The MPEG-DASH Standard for Multimedia Streaming Over the Internet

Abstract: MPEG has recently finalized a new standard to enable dynamic and adaptive streaming of media over HTTP. This standard aims to address the interoperability needs between devices and servers of various vendors. There is broad industry support for this new standard, which offers the promise of transforming the media-streaming landscape.

Session-based DASH streaming: a new MPEG standard for customizing DASH streaming per session

Abstract: The MPEG DASH standard is widely deployed in over-the-top streaming services. The standard defines two key components: a manifest format to describe the presentation and a set of segment formats to describe the media segments. While the DASH's manifest format, Media Presentation Document (MPD) provides a set of extensive tools to describe the presentation timeline, this document is usually created for a large set of DASH clients and therefore it can be cached in CDNs for a large population. If the MPD needs to be customized per client, the cache efficiency of storing a single MPD for all clients would be lost. Recently the MPEG Systems Working Group (ISO/IEC/SC29/WG3) developed a new standard that allows an MPD to be customized at each client using an external document and a set of processing rules. The first version of the Session-Based DASH standard (ISO/IEC 23009-8) was recently finalized and will be published in the upcoming months. ISO/IEC 23009-8 defines 3 components: 1) A Session-Based Document (SBD) which defines the MPD customization rules for a client for a given session, 2) A method of referencing the external Session-Based Document (SBD) in the DASH MPD, and finally, 3) a processing model for the client-side processing of SBDs. The SBD defines a post-processing procedure to customize each URL generated by the DASH client from an MPD. Before the DASH client requesting to download a resource using that URL, a process that is described in the SBD document is applied to the URL. The process can customize different parts of the URL, i.e. the host, path, port parts as well as its queries, using a template matching technique. The customization can be timed dependent, on the point in the media timeline that the URL corresponds to, or order dependent, i.e., on the location of the URL in the URL request orders. The result is a customized URL per client/session/URL that is produced from the given URL generated by the DASH client from MPD. The ISO/IEC 23009-8 standard defines an architecture for the session-based DASH streaming that has a few benefits: 1) From the content creation side, it separates the client-based and session-based customization from MPD and therefore maintains the MPD caching efficiency while allowing the customization. It also enables to produce customization after packaging of MPD which means that it can be added to the current workflows as a post-processing step. 2) From the client-side, it allows implementation of SBD client as a separate and independent process from the DASH client, and therefore it can be added to the current clients as a separate process. Furthermore, the SBD processing can occur on the device or a different network entity such as application servers. 3) From the content distribution side, the SBD creation or customization can occur at different nodes of the network, at the origin server, as distribution centers and CDNS, or even at the home network gateways. The standard also allows multiple SBDs to be applied to the URLs of an MPD, enabling the customization to be requested by one or multiple entities in the ingest or distribution chain. In this paper, we first describe the session-based DASH streaming architecture. Then the features of the SBD standard are outlined including the capabilities of customizing based on templates as well as the key-pair replacement and the possibilities of replacing various parts of a URL. Next, the SBD client processing model is described, and how the SBD client can be implemented on the device or as a network entity as a separate process. Finally, we demonstrate a forensic watermarking application using the SBD and demonstrate its capabilities and compare the efficiency of watermarking using the SBD standard vs the MPD customization per client/session.

A Control-Theoretic Approach for Dynamic Adaptive Video Streaming over HTTP

Abstract: User-perceived quality-of-experience (QoE) is critical in Internet video applications as it impacts revenues for content providers and delivery systems. Given that there is little support in the network for optimizing such measures, bottlenecks could occur anywhere in the delivery system. Consequently, a robust bitrate adaptation algorithm in client-side players is critical to ensure good user experience. Previous studies have shown key limitations of state-of-art commercial solutions and proposed a range of heuristic fixes. Despite the emergence of several proposals, there is still a distinct lack of consensus on: (1) How best to design this client-side bitrate adaptation logic (e.g., use rate estimates vs. buffer occupancy); (2) How well specific classes of approaches will perform under diverse operating regimes (e.g., high throughput variability); or (3) How do they actually balance different QoE objectives (e.g., startup delay vs. rebuffering). To this end, this paper makes three key technical contributions. First, to bring some rigor to this space, we develop a principled control-theoretic model to reason about a broad spectrum of strategies. Second, we propose a novel model predictive control algorithm that can optimally combine throughput and buffer occupancy information to outperform traditional approaches. Third, we present a practical implementation in a reference video player to validate our approach using realistic trace-driven emulations.

Improving fairness, efficiency, and stability in HTTP-based adaptive video streaming with FESTIVE

Abstract: Many commercial video players rely on bitrate adaptation logic to adapt the bitrate in response to changing network conditions. Past measurement studies have identified issues with today's commercial players with respect to three key metrics---efficiency, fairness, and stability---when multiple bitrate-adaptive players share a bottleneck link. Unfortunately, our current understanding of why these effects occur and how they can be mitigated is quite limited.In this paper, we present a principled understanding of bitrate adaptation and analyze several commercial players through the lens of an abstract player model. Through this framework, we identify the root causes of several undesirable interactions that arise as a consequence of overlaying the video bitrate adaptation over HTTP. Building on these insights, we develop a suite of techniques that can systematically guide the tradeoffs between stability, fairness and efficiency and thus lead to a general framework for robust video adaptation. We pick one concrete instance from this design space and show that it significantly outperforms today's commercial players on all three key metrics across a range of experimental scenarios.

Method and apparatus for video coding and decoding

Abstract: A method comprises receiving a first sequence of access units and a second sequence of access units; decoding at least one access unit of the first sequence of access units; decoding a first decodable access unit of the second sequence of access units; determining whether a next decodable access unit in the second sequence of access units can be decoded before an output time of the next decodable access unit in the second sequence of access units; and skipping decoding of the next decodable access unit based on determining that the next decodable access unit cannot be decoded before the at least one of the decoding time and the output time of the next decodable access unit.

Dynamic adaptive streaming over HTTP dataset

Abstract: The delivery of audio-visual content over the Hypertext Transfer Protocol (HTTP) got lot of attention in recent years and with dynamic adaptive streaming over HTTP (DASH) a standard is now available. Many papers cover this topic and present their research results, but unfortunately all of them use their own private dataset which -- in most cases -- is not publicly available. Hence, it is difficult to compare, e.g., adaptation algorithms in an objective way due to the lack of a common dataset which shall be used as basis for such experiments. In this paper, we present our DASH dataset including our DASHEncoder, an open source DASH content generation tool. We also provide basic evaluations of the different segment lengths, the influence of HTTP server settings, and, in this context, we show some of the advantages as well as problems of shorter segment lengths.

Developing a predictive model of quality of experience for internet video

Abstract: Improving users' quality of experience (QoE) is crucial for sustaining the advertisement and subscription based revenue models that enable the growth of Internet video. Despite the rich literature on video and QoE measurement, our understanding of Internet video QoE is limited because of the shift from traditional methods of measuring video quality (e.g., Peak Signal-to-Noise Ratio) and user experience (e.g., opinion scores). These have been replaced by new quality metrics (e.g., rate of buffering, bitrate) and new engagement centric measures of user experience (e.g., viewing time and number of visits). The goal of this paper is to develop a predictive model of Internet video QoE. To this end, we identify two key requirements for the QoE model: (1) it has to be tied in to observable user engagement and (2) it should be actionable to guide practical system design decisions. Achieving this goal is challenging because the quality metrics are interdependent, they have complex and counter-intuitive relationships to engagement measures, and there are many external factors that confound the relationship between quality and engagement (e.g., type of video, user connectivity). To address these challenges, we present a data-driven approach to model the metric interdependencies and their complex relationships to engagement, and propose a systematic framework to identify and account for the confounding factors. We show that a delivery infrastructure that uses our proposed model to choose CDN and bitrates can achieve more than 20\% improvement in overall user engagement compared to strawman approaches.