Ancillary Data Monitoring in Multiviewers

Author: Dennis Lennie

Published 1st September 2009


The broadcast environment has gone through enormous change over the last decade, creating challenges in the management, storage and broadcast of material. Factors contributing to these challenges include the increase in the number of channels with the move to digital, the introduction of various aspect ratio and video standards with the transition to HD, and the necessary evolution from tape to file-based workflows.
In order for broadcasters to manage a significantly increased volume of content and numerous properties, baseband video today must be tagged with information. Aspect ratio (AFD/WSS), program ID, station ID time code are all important indicators that must be captured along with video and audio content in order to correctly broadcast and store content for future use. Alongside this “data about data,” there is other information vital for broadcast such as closed captioning/subtitling, teletext, content rating data (VCHIP), various audio channels (including different language options) and, increasingly common, Dolby E audio data.
Because ancillary data monitoring has become a critical aspect in certain aspects of today’s broadcast workflow, it is essential that monitoring equipment such as multiviewers feature the ability to decode and render this data to produce the exact result the consumer at home will experience.
The different application areas within a broadcast facility have varying requirements for ancillary data monitoring. For example, because production control rooms by their nature are primarily concerned with the content they are shooting, limited metadata analysis is required. Timers, audio levels and camera idents are the primary data sources that need to be monitored.
The master control room is the area where metadata monitoring becomes critical. At this point, before the feed is taken to transmission, it is important that the metadata is properly analyzed to ensure it is present and correct. The cost of missing or corrupt data can be significant — some items such as closed captioning are mandatory and can lead to fines if missing. Other data such as aspect ratio data affect the way the picture is viewed at home; an incorrect setting could lead to important parts of the image going missing. Operators viewing dozens of channels need all the help they can get to help monitor the status of this number of indicators.
A cable headend will concern itself with ensuring none of the data needed for consumer viewing will have been lost during the transmission process. Again, subtitling, teletext and aspect ratio markers are monitored, while basic video and audio monitoring alarms such as loss, black picture and frozen picture are an absolute necessity.
At the heart of every modern control room is a multiviewer, which must be capable of displaying all this necessary information to the operator and raising alerts as needed. The quantity and various functionality of the metadata present a challenge that requires a high level of sophisticated processing.
Ancillary data is typically stored in packets along with the blanking period of video, and both are identified by unique data sequences that distinguish the type and size of information. This data must be stripped from the incoming video and taken to separate processing blocks. In some cases it is necessary only to render the data. For instance, to display the timecode, the data is extracted and burned on to the video; in other cases, such as audio extraction, there is further processing needed to calculate ballistic data or phase information.
This amount of processing is a heavy but necessary overhead. Modern multiviewers have evolved from simple screen splitters to key tools for monitoring video and detecting faults. With the noted increase of channels and ancillary data, the multiviewer must step up to the challenge — flagging missing data, providing flexible notification measures and alarm management tools and, if possible, correcting the fault.
As a result, the IQ of multiviewers has risen significantly over recent years. Where once only core video processing was needed, today, extra technology has been added to process ancillary data, render on-video graphics and manage automated responses. Alongside the multiviewer, management or supervisor software is now also evolving.
Every facility has its own particular requirement for data monitoring; what is important is for the broadcaster to find a solution that monitors to the various types of data, identifies and reports error conditions and allows the user the flexibility to automate their response and notify the correct personnel.
The need for monitoring metadata is obvious: the data that affects the user’s experience must be monitored to ensure it is correct and data is not lost, while the technical information is needed to help identify and manage content. When choosing a multiviewer for a modern control room, the application (production, master control, etc.), the number of channels and the type of data services employed, as well as the quality of management software and response automation available, are all requirements that should be carefully considered.
Ancillary data is a key prerequisite in the current broadcast chain. Ensuring it is correct and present is something that should be at the heart of multiviewer-based monitoring specifications.

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