ATSC transport stream data services

Crawls, bugs and other superimposed graphics or animations sometimes impede the enjoyment of watching a broadcast. Years ago they were interesting differentiating features, but now they frequently divert attention away from the program. Wouldn’t it be wonderful to control what can be seen on the screen, or ask for more info, purchase an item or see an extended commercial? Imagine that, a viewer that actually requests to see a longer commercial!

Once simply used for audio, video and program guides, ATSC transport stream (TS) standards have expanded to define algorithms that facilitate data delivery. The common receiver can be an HDTV, STB, PC or any other presentation device. Simultaneously, a BOC must also expand its infrastructure in support of enhanced features.

Flow downstream

TS data delivery standards facilitate applications such as enhanced television, Webcasting, and streaming video services. Interoperable standards will make this technology transparent to the viewer, easy to use, reliable and secure. They are the enabling technologies of what is envisioned as the media networked home of tomorrow.

Before diving into the formal documents it would be helpful to get an overview of the ATSC data TS methodology. A Broadcast Engineering article by Richard Chernock and Jerry Whitaker, and a University of Virginia Web site are good places to start.

The foundation of all data delivery standards is the ATSC Standard A/90 Data Broadcast Standard. It defines protocols for download of data, delivery of datagrams compatible with digital multiplex transport streams. The standard supports data services that are both TV program-related and non-program related. A/91: Implementation Guidelines for the Data Broadcast Standard provides a set of guidelines for the use and implementation of ATSC A/90 Data Broadcast Standard.

ATSC working and study groups have recommended additional standards using A/90 as their basis. Many have been adopted. Together, this suite of specifications enables interoperability among applications by providing a common protocol.

Software updates or upgrades of firmware, operating system software and device driver software can be accomplished via data in the TS. A/94: ATSC Data Application Reference Model defines an application reference model (ARM). A/95: Transport Stream File System Standard (TSFS) defines the standard for delivery of directories and files. And A/97: Software Download Data Service specifies a data service that may be used to download software.

Paddle upstream

Killer apps are sought after like treasure, and the killer app of HDTV may be interactive TV (ITV). ITV is a capability enabling technology, while the actual features the standards facilitate are the real killer apps. Interactivity requires the use of a two-way interaction channel that enables communications between the client device and remote servers, the backchannel.

The backchannel scenario differs for each delivery mechanism. Over the air transmission lacks a backchannel. DBS also suffers from lack of a backchannel. Cable systems have a built-in backchannel.

The common receiver

Interactive and enhanced applications need access to common receiver features in a platform-independent manner. A/100: DTV Application Software Environment - Level 1 (DASE-1) adopted in 2002, defines middleware that permits programming content and applications to run uniformly on all brands and models of receivers.

DASE is specified in eight parts. An overview of the implementation can be gained by a reading of A/100-1, DASE-1 Part 1: Introduction, Architecture, and Common Facilities. The other parts specify a declarative and procedural application environment, API, security and other relevant modules.

Frequently, by the time a technology gets through the standardization process, an improvement has come along. Similarly, in less than three years, DASE is now the basis of a proposed ATSC standard that enables interactive features. The Advanced Common Applications Platform (ACAP) specification seeks to ensure interoperability between ACAP applications and different implementations of platforms supporting ACAP. ACAP is intended to apply to broadcast systems and receivers for over-the-air broadcast and cable TV systems but may also be applied to other transport systems such as satellite.

Completing the interactive suite, A/93: Synchronized/Asynchronous Trigger Standard facilitates transmission of synchronized data elements, and synchronized and asynchronous events. A/96: ATSC Interaction Channel Protocols defines a core suite of protocols to enable remote interactivity in television environments.

BOC implementation of TS data standards

In the BOC an automated Internet-like data download infrastructure must be created. Applications must be authored or purchased and the transport stream multiplexed. Provisions for reception of backchannel data must be implemented as well. This may be considerably more complicated than transitioning to HDTV broadcasting and will require many varied technical talents. Because no one person can know everything, project management and team building are essential for success.

The ATSC Implementation Subcommittee's Data Implementation Working Group (DIWG) has issued a report, Implementation of Data Broadcasting in a DTV Station, that describes interconnections between the components of DTV data broadcast equipment and flow control for opportunistic data broadcast and data synchronization.

Awakening to the potential of ATSC TS data standards

Targeted advertising technologies using ATSC data standards are now being deployed. When integrated with Internet-like permission-granted tracking and preference capabilities, targeting advertising could deliver an increased return with customized commercials for specific demographics.

For example, a cruise line could produce a commercial template, then shoot addressable segments targeted by certain demographics: families with young children, singles or senior citizens. Just-In-Time assembly of demographically relevant commercials facilitates insertion of personalized-addressable segments to demographically appropriate viewers. The spot would then close with a regional “where to purchase” tag line.

Another possible use of ATSC data standards may be enhanced services. For example, a news broadcast could add a button to click on for story background, biographical information, historical context or other information.

Will HDTV replace the Internet?

Eventually, the Internet will be fully integrated with every device in a home media network. The A/92: Delivery of IP Multicast Sessions over Data Broadcast Standard specifies the delivery of Internet Protocols (IP) Multicast sessions, the delivery of data for describing the characteristics of a session, and usage of the ATSC A/90 Data Broadcast Standard for IP Multicast. This is the first step in getting HDTV on the Web. Adding a backchannel will complete the implementation.

The marriage of broadcast and IT has been consummated in the ATSC data services standards, will live happily ever after in the home digital networks of the future.


PSIP and data broadcasting: Keys to making the ATSC A/90 standard work
By Richard Chernock and Jerry Whitaker, Oct 1, 2002

Standardization Efforts

Further reading


Interactive TV

Personal Home Digital

W3C Recommendation - Jan. 7,

Technical correction: Reader Robert Gross points out that in the May 16, 2005, issue of Transition to Digital, "ATSC transports streams," it was incorrectly stated that " …there is a defined relationship between video and audio PIDs for a given program".

As he notes: "This was present in the original version of the standard (ATSC A/53) and was known as the program paradigm. The program paradigm was dropped from the standard in later versions. The video and audio PIDs for each program are listed in the Program Map Table for that program and referenced in the Service Location Descriptor of the Virtual Channel Table."

Thanks for setting the record straight.

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