Kevin J. Ma

Mobile video delivery with HTTP

Expansion in 3G cellular coverage and the emergence of more powerful mobile devices has increased demand for massively scalable mobile video delivery. The rapid adoption of the third screen as a primary screen for video has highlighted inefficiencies in the mobile delivery ecosystem and scalability issues in the mobile delivery infrastructure. This article provides an overview of the current mobile content delivery ecosystem and discusses the expanding role of HTTP-based mobile video delivery. A new class of HTTP-based mobile delivery protocols seeks to address existing quality and scalability issues by simplifying and standardizing mobile video delivery. This article shows how segment-based delivery has enabled HTTP-based live streaming and dynamic bitrate adaptation while increasing scalability through the use of existing CDN infrastructure.

Review: A survey of schemes for Internet-based video delivery

This survey looks at how traditional networking techniques (e.g., caching, traffic shaping, path diversity, and load balancing) have been adapted to address the needs of Internet-based video delivery. The stringent timing and relatively high bandwidth requirements of video traffic are taxing on best-effort networks and many video specific protocols and delivery methods have emerged over time in an attempt to mitigate network limitations. Video quality is directly tied to the underlying networks ability to deliver data in time for playout. This paper surveys three classes of techniques which have been proposed for improving the quality of Internet delivered video: network load reduction, network interruption mitigation, and network load distribution. We discuss how each of these paradigms is applied within the different segments of the end-to-end video delivery system: by the server, in the network, or at the client, with a focus on how the underlying network conditions affect video quality optimization.

HTTP Live Streaming Bandwidth Management Using Intelligent Segment Selection

HTTP-based segmented delivery has become a popular choice for video distribution. The ability for clients to explicitly perform dynamic bitrate adaptation on segment boundaries has allowed clients to optimize the end user viewing experience. Client-based rate adaptation schemes, though, are typically greedy in nature and within the context of the network as a whole, these schemes may be sub-optimal. In this paper we propose a congestion-aware rate adaptation scheme that works on top of existing segmented delivery protocols to provide network bandwidth management and fairness. We examine the HTTP Live Streaming approach and compare our community-based approach with the native Apple® implementation, though the framework is extendable to other protocols. We show the improved user experience with our scheme through higher quality video delivery and lower bitrate selection thrashing.

Video Rate Adaptation in Mobile Devices via HTTP Progressive Download of Stitched Media Files

Network intensive video delivery often employs dynamic rate adaptation to trade off video quality for lower bandwidth. In this letter we describe a scheme for providing deterministic rate adaptation (RA) for mobile devices with limited native media player capabilities. The proposed scheme provides a client-side proxy and stitched media file (SMF) architecture for using native media player seek operations to perform RA. The proxy uses standard HTTP for retrieving the SMF from standard HTTP servers via reliable, optimized content delivery networks. The SMF concatenates multiple bitrate encodings in a single file enabling seek-based RA. Low latency seek operations provide finer granularity RA and lower latency rate switches compared with segment-based RA schemes.

Scalability of HTTP pacing with intelligent bursting

The ubiquity and simplicity of HTTP makes it a popular choice for Web-based video retrieval. However, HTTP was not designed for retrieving data with just-in-time tolerances; HTTP servers have always taken an as-fast-as-possible approach to data delivery. For media with known bandwidth constraints (e.g., audio/video files), HTTP servers can be enhanced and optimized by taking these constraints into account. For these data types, we present our architecture for an HTTP streaming server using paced output with intelligent bursting. We also discuss the scalability advantages of our HTTP streaming server architecture and compare it with traditional HTTP server response times and bandwidth usage.

DRM workflow analysis for over-the-top HTTP segmented delivery

Monetization of premium video content requires two key components: quality and security. In the mobile space, quality issues have been largely address in recent years through faster CPUs and segment-based HTTP adaptive bitrate delivery (e.g., Apple® HTTP Live Streaming, Adobe® HTTP Dynamic Streaming, and Microsoft® Silverlight™ Smooth Streaming). This has enabled plethora of new services to deliver high definition video to smart phone and tablet devices. This in turn has brought mobile digital rights management (DRM) under increased scrutiny. Existing DRM guidelines are geared toward monolithic file distribution to fixed end-points. The emergence of segment-based HTTP distribution protocols has produced unforeseen issues in existing content delivery workflows. Support for over-the-top (OTT) delivery has further complicated DRM enforcement. In this paper we analyze the impact of segmented OTT delivery on traditional content preparation and distribution workflows. We discuss the use of pipelining for optimizing transcoding, segmentation, and encryption workflows. We also address security and scalability concerns related to key generation, device registration, and key distribution workflows. Together, these workflows provide the necessary components for an efficient and secure OTT content delivery platform.

DRM optimization for stitched media file rate adaptation

Digital rights management (DRM) and video quality are two important issues for content providers. DRM plays a critical role in enforcing monetization policies while video quality is key for protecting brand integrity. For stitched media file-based (SMF) rate adaptation schemes which rely on low latency seek operations, a seek friendly DRM encryption scheme is required. This paper describes our stream cipher-based DRM encryption scheme which enables secure SMF rate adaptation. We provide a model for and discuss the trade-offs involved in optimizing rate adaptation latency within our scheme. Our SMF scheme is one of a number of HTTP video delivery implementations that we have commercially deployed on the AndroidTM and Blackberry® mobile platforms and that use our DRM. Though the DRM scheme works with both SMF and segment-based approaches, this paper focuses on SMF considerations. We include cipher performance results from actual device tests, as well as rate adaptation latency results from our production implementation.

Throughput-delay tradeoff in small and sparse mobile ad hoc networks

This paper takes the first step in characterizing the throughput-delay tradeoff for small and sparse MANETs which have many practical applications. We find that as the MANET becomes sparser, throughput decreases and delay increases, as expected. If relaying is disabled then the throughput and delay depend on the size of the area of operation. While relaying does increase throughput, the single packet relaying strategy worsens the delay for small MANETs in the Grossglauser traffic model. Greedy relaying overcomes this worsening without trading throughput, but only for rapidly mixing mobility. Unlike in dense networks, local broadcasting does not provide any significant benefit. Packet repetition does decrease delay, but only at the expense of reduced throughput. Our results are useful in practical underwater MANETs which are typically small and sparse.

CoS enforcement for HTTP adaptive streaming

As the HTTP-based segmented video delivery paradigm continues to grow in popularity, the ability to enforce differentiated classes of service (CoS) across large numbers of clients becomes increasingly important. Differentiated services are an important monetization technique for content service providers. In over-the-top (OTT) video delivery, client-based CoS enforcement is necessary for federated delivery across multiple operator networks. In this paper, we address the question of how to implement distributed client-based CoS enforcement for OTT video delivery. Our solution integrates CoS-awareness into the client rate adaptation algorithm using segment download aborts to enforce relative bandwidth virtualization. This scheme does not require the client to be aware of other clients in the network or of specific network resource limitations. We compare our distributed approach with manifest-based CoS enforcement and provide simulation results which demonstrate the network utilization advantages of our approach.