A Guide to Ensuring Digital Video Service Quality Primer Primer 2 www.tek.com/video-quality-service-assurance A Guide to Ensuring Digital Video Service Quality Table of Contents Introduction ....................................................................4 Using QoE Scoring Methods to Develop a Service Benchmark ................................................23 Section 1: Digital Video Content Readiness .................5 Detecting Artifacts and Impairments before Containers, Mezzanines, and Codecs ...............................5 Subscribers ...............................................................23 When Data Becomes Metadata ........................................6 Perceptual Video Quality: Compression and Encoding Artifacts .....................................................24 The Challenge of Quality Control ..............................7 Regulatory Compliance ..................................................26 QC Methodology: Human vs. Automated Monitoring ........7 Closed Captioning .....................................................26 Types of Errors: What Could Possibly Go Wrong? ............7 Audio Loudness ........................................................27 QC Tests, Checks, and Results ........................................8 Ad Verification.................................................................28 Examples of Content Readiness Testing in RF Monitoring .................................................................30 Cable Workflows ........................................................9 New Requirements for Monitoring OTT & Adaptive Bit Rate ............................................................31 Video on Demand .............................................................9 The QC “Pre-Flight” Check ........................................10 Summary ..................................................................34 Ad Insertion ....................................................................11 Ad QC .......................................................................12 Section 3: Network Troubleshooting & Diagnostics ...35 Adaptive Bit Rate ............................................................13 Troubleshooting Background .................................35 “Segmenting” and QC Issues ....................................14 Troubleshooting QoS ...............................................36 Automating File-Based QC .....................................15 Semi-Automated QC Workflows .....................................15 Troubleshooting QoE ...............................................40 Asset Management and the Fully Automated Workflow ........................................................................16 How are QoS and QoE Interrelated? ......................42 QC Reporting .................................................................17 Using QoS and QoE to Identify “Real” Problems: How is a Workflow Like a Web Browser?........................17 Troubleshooting Case Studies ................................43 When Systems Communicate ........................................18 Video QoE ......................................................................43 Summary ..................................................................18 Audio QoE ......................................................................44 Troubleshooting Over-Compression ................................44 Section 2: Live Network Monitoring of Digital Video Troubleshooting Interoperability ......................................44 Services ........................................................................19 Troubleshooting Transport Streams with CaptureVu ........45 Live Network Monitoring Background .............................19 Troubleshooting Ad Insertion ..........................................46 Quality of Service (QoS) vs. Quality of Experience (QoE) ............................................................20 Summary ..................................................................47 QoS Monitoring Tradeoffs ..........................................22 References ...............................................................47 Key Video Quality Monitoring Locations .....................22 www.tek.com/video-quality-service-assurance 3 Primer The second part, Live Network Monitoring, involves ensuring Introduction both the Quality of Service (QoS) and the Quality of Experience Digital television has transformed the television viewing (QoE) in real time across hundreds of digital services. experience and has offered Video Service Providers the ability Understanding the difference between QoS and QoE as well to deliver hundreds of channels of programming with better as how Perceptual Video Quality relates to QoE is crucial for picture and sound quality. Since digital television was first any monitoring deployment. Knowing what, where and how launched, there have been a great deal of new technologies to monitor leads to reduced trouble calls, a faster ability to and capabilities to emerge including HDTV, digital ad insertion, detect and repair issues, reduced churn and a reduction in tru2way, MHP, VOD and most recently—multiscreen or OTT operational expenditures. (Over The Top) video. As networks converged and service The final part of the workflow isNetwork Troubleshooting, offerings increased, Video Service Providers have dealt with which is important to help quickly identify and log the audio the ongoing, arduous task of ensuring the quality of these or video problem that occurred, then identify or pinpoint the services for their subscribers. equipment (or network link) that needs attention. To identify The first part of the digital video delivery workflow,Content and isolate problems, it is critical to have access or test points Readiness, focuses on having all your On Demand content throughout the facility. The minimum set of test points in any available in a form and condition suitable for distribution. network should be at the point of ingest where the signal It means content that’s not only free from objectionable comes into the facility, the ASI or IP switch, and finally egress distortion but also equipped with the right markers and where the signal leaves as IP or RF. To begin testing a signal metadata and resolution to deliver the best possible service that may contain the suspected issue, both QoS and QoE to subscribers, regardless of the receiving platform. This level methods are used. Both methods are useful in troubleshooting of Content Readiness calls for a rigorous quality control (QC) and analysis, but each of the two methods quantify issues program that inspects every individual file—from a 15-second using completely different metrics. ad to an HD movie—as it enters the cable plant and when it In this Guide to Ensuring Digital Video Service Quality, we will is stored for eventual play out. The sheer volume of content examine three parts of the digital video delivery workflow, and dictates some level of automation in the QC process. the tools and methods to ensure the QoS and QoE of your digital video services. 4 www.tek.com/video-quality-service-assurance A Guide to Ensuring Digital Video Service Quality Section 1: Digital Video Content Codec Container Bit Rate Readiness DV MXF Op-Atom 100 Mb/s MPEG-2 IMX MXF OP1a 30–50 Mb/s Containers, Mezzanines, and Codecs Apple ProRes QuickTime 220 Mb/s The file-based workflow begins with an ingest server whose VC-3 MXF or QuickTime 220 Mb/s job is to process received content into files that facilitate Table 1.1. Commonly-used mezzanine file formats and codecs. management, storage, and distribution. Content arrives in diverse formats and it is necessary to process everything into …and more. Some formats are optimized for playout, others a uniform format for internal use. for editing or capture or other points in the workflow. The The output of this process is digital files organized into common MXF container format alone has multiple variants. “containers,” also known as wrappers. A container usually Containers are a cornerstone of file-based workflows. embodies a single file, though some containers may be made In the cable domain, MPEG Transport Stream files are of up of multiple files linked together. In any case containers course ideal for playout, ready to be packetized and sent out encompass all the vital information about the files they contain: over the network. The .TS container format can be used for compressed video, audio and also importantly, metadata. offline processing and QC operations as well. In addition the There is no single universal container format. In fact there is a Quicktime and MXF formats, among others, are well suited to variety of container formats including: editing and transcoding (converting) by means of codecs such as those in Table 1.1. MPEG Program Stream MPEG-2 Transport Stream MP4 3GP QuickTime File Format Material Exchange Format (MXF) General Exchange Format (GXF) Advanced Systems Format (ASF) www.tek.com/video-quality-service-assurance 5 Primer Figure 1.1. Mezzanine formats allow efficient handling and storage of files within the cable plant. MXF and QuickTime formats are commonly used as When Data Becomes Metadata “mezzanine files.” The term comes from the world of Metadata is often stored in the file with the video and audio architecture, where it denotes an intermediate floor (often data, or it can be located in an auxiliary file in the same a lobby or a balcony) between two main floors. Similarly, package. Metadata is overarching “data about the