IS Findings are documents developed by the ATSC Implementation Subcommittee on various aspects of the digital television transition. They provide practical guidance on station operation and design. IS Findings may also identify aspects of the DTV transition requiring additional study, including development of standards, recommended practices, and/or information documents.

IS-095 – Top Down Summary Report

30 October 1998, Download PDF File

In an effort to speed the transition to digital television broadcasting, the Implementation Subcommittee of the ATSC undertook an effort to inventory the various systems and their interfaces that could potentially exist in a typical station, regardless of the chosen implementation scenario. This inventory was intended to serve as a guide of sorts to point to the standards that exist for equipment interfaces, identify potential conflicts between those standards, and identify areas where standards and/or technology need further development.

IS-151 – Implementation of Data Broadcasting in a DTV Station

18 November 1999, Download PDF File

This document contains a series of recommendations developed by the ATSC Implementation Subcommittee's Data Implementation Working Group (DIWG) for the implementation of data services in an ATSC emission station. It covers interconnections between the components of a DTV data broadcast, management and provisioning parameters common to data broadcast equipment, flow control for opportunistic data broadcast and data synchronization.

IS-161 – PTS Time Stamping Bit Streams

6 January 2000, Download PDF File

This document discusses MPEG-2 time stamping of AC-3 bit streams considering the complication and potential ambiguity caused the overlap add process employed within the AC-3 filterbank. The behavior of the software AC-3 encoders and decoders, which are often used to create and analyze test bit streams, is also described. This note presumes a 48 kHz sample rate when discussing time periods of blocks and frames.

IS-190 – Essential Information to be Carried in DTV Program Streams

25 October 2001, Download PDF File

There is a need for certain information related to digital television programs to be stored and transported within and between television facilities. The ATSC Implementation Subcommittee considers this information to be essential for the proper operation of both professional and consumer digital television equipment. Most of this associated information is metadata about the program stream elements, however, some of it is related data essence. Although the storage and/or transport of program streams may take many forms—i.e., videotape, data tape, servers, radio frequency transmissions, or terrestrial circuits—there is a common need to preserve and transmit this information.

IS-191 – Relative Timing of Sound and Vision for Broadcast Operations

26 June 2003, Download PDF File

These findings address end-to-end DTV system latency, specifically unequal delays that can be imposed on the audio and video signals. Specific guidelines are given for four identified elements of the program chain from origination to the consumer.

IS-214 – Program Interchange Identification Requirements and Solutions

28 July 2001, Download PDF File

Current practice in the identification of programs during the production and distribution processes, including program interchange between organizations, involves human-readable labels and, sometimes, machine-readable labels attached to physical media, with no widely accepted standards for such labeling. Any identification information embedded within the content consists of opening slates recorded in the video that must be read by humans. Programs are often accompanied by format sheets that provide the timing of segments within the programs, but the timings so provided are often suspect and require verification if tight control of program integration is to be maintained.

To achieve the greatest benefit to the industry in terms both of accuracy of program release and integration, and of labor savings through use of automation, it is necessary to establish standard methods for carrying the required information together with program content. A number of essential underlying techniques that will enable meeting of the requirements have been developed over the last few years. Now it is necessary to examine the overall system so as to develop a complete set of requirements and then to standardize the necessary solutions to those needs.

IS-232 – DTV Transport and Data Interfaces

17 May 2002, Download PDF File

This document lists currently used input and output interfaces for encoders and multiplexers.

IS-266 – Report on Latency and Timing Issues

13 June 2002, Download PDF File

Programs starting and finishing at unpredictable times can cause great inconvenience to viewers, particularly if they are trying to view or record successive programs on different stations. This is a serious problem, which to avoid upsetting the viewing public, broadcasters will have to address in the near term.

IS-277 – Assessment of Data Content/Delivery for Control of the Digital Broadcast Transport Stream and PSIP Generation

25 September 2002, Download PDF File

These findings result from an investigation carried out by ATSC Implementation Subcommittee PSIP Working Group during the period February – September 2002, and were adopted by the IS on 24 September 2002. They reference an informative document from the ATSC IS PSIP Working Group, Assessment of Data Content and Delivery for Control of the Digital Broadcast Transport Stream and PSIP Generation, dated 24 September 2002.

IS-312 – Optimization of Image Formatting for Transmission and Display

9 June 2004, Download PDF File

Existing HDTV receivers do not always display HD and/or SD program material in the optimum or most pleasing manner considering the aspect ratio of the original and transmitted image size and shape. Similarly, broadcasters do not always optimize the image format of program material for simulcast NTSC and DTV channel transmission. Parameters for aspect ratio, AFD, and bar data are defined in A/53C but these are not being fully utilized by broadcasters, professional equipment, and consumer receiver and display products. Professional broadcast equipment tools are available to assist with optimization of image formats but these are frequently not used or only partially utilized by program producers and broadcasters. The ATSC Implementation Subcommittee (IS) finds that there is a need for further work by the ATSC, CEA, and SMPTE to review and further analyze the considerations and issues identified in the document with the goal of producing one or more recommended practices for use by broadcasters and professional and consumer equipment manufacturers, related to the optimization of image formatting for transmission and in receivers and video displays.

IS-318 – Multichannel Audio Program Delivery and Metadata Considerations (Pre-emission)

10 September 2004, Download PDF File

The successful delivery of high-quality multichannel audio begins with a descriptive and accurate program delivery specification. As has been the case since the days of monophonic audio, it is imperative that broadcasters require that audio be delivered in a standard and consistent manner. These basic requirements still hold true for multichannel audio, and expand to encompass proper audio metadata. An introduction to audio metadata is presented, giving a list of all of the parameters, then a detailed treatment of the three most important parameters: Dialogue Level, Dynamic Range Control, and Downmixing- better known as the Three D’s. Finally, six typical program scenarios are presented. Signal flow is followed from initial production, through delivery to the network, distribution to the local station, and reception by the consumer. A list of recommended metadata parameters for each scenario is also included.