Co-ordinates television standards among different communications media focusing on digital television, interactive systems, and broadband multimedia communications. Also developing digital television implementation strategies
Adopted by U.S., Canada, S. Korea, Taiwan and Argentina
– For equal data rate, COFDM requires more than twice as much power as VSB to achieve equal coverage, causing much more interference into analog service, making DTV channel assignments much more difficult
• Relaunch of U.K. DTV service with more robust transmission scheme only delivers13.6 Mbps in a 6 MHz channel, compared to 19.4 Mbps for ATSC/VSB!
– VSB’s additional 2.5 dB advantage in peak-to-avg. ratio means COFDM transmitters would require much higher procurement and operation costs
– VSB offers better impulse noise performance than DVB-T, a crucial difference for the ability to use VHF channels
– VSB receiver improvements have eliminated multipath performance problems
Dolby AC-3 multi-channel audio
– Consistently better performance than MPEG Layer-II at equal bit rates
– AC-3 is already the de facto worldwide standard, now available as an option with DVB
DASE : D TV A pplication S oftware E nvironment, which is defined by ATSC Specification a_100_1 ~ a_100_8
ATSC A/100_1: DASE-1 Part 1: Introduction, Architecture, and Common Facilities . Introduces the DASE Standard, defines the DASE Architecture, and specifies Common Facilities which must be processed by both the DASE declarative application environment and the DASE procedural application environment.
ATSC A/100_2: DASE-1 Part 2: Declarative Applications and Environment , specifies all facilities which are specifically processed by the DASE declarative application environment
ATSC A/100_3: DASE-1 Part 3: Procedural Applications and Environment , specifies all facilities which are specifically processed by the DASE procedural application environment.
ATSC A/100-4, DASE-1 Part 4: Application Programming Interface , specifies the syntax and semantics of the DASE specific APIs exposed to DASE Procedural Applications.
ATSC A/100-5, DASE-1 Part 5: ZIP Archive Resource Format , specifies an archive content type supported by the common facilities.
ATSC A/100-6, DASE-1 Part 6: Security , specifies all facilities which relate to the common security aspects of DASE Applications and DASE Systems.
ATSC A/100-7, DASE-1 Part 7: Application Delivery System – ARM Binding .Specifies all facilities which relate to the binding of DASE Applications and the DASE System to the ATSC Data Application Reference Model (A/94), which, in turn, specifies an application delivery system which employs the ATSC Data Broadcast Standard (A/90).
ATSC A/100-8, DASE-1 Part 8: Conformance , specifies the overall conformance requirements for DASE Applications and DASE Systems.
DASE Content is generally organized as a collection of one or more DASE Applications, each of each of which takes the form of either a declarative application or a procedural application.
Declarative Applications A DASE declarative application (DA) is a DASE Application whose initial entity is the specific markup content type application/xhtml+xml. In addition to markup content, a DASE declarative application may contain stylesheet and script content as well as other content types.
Procedural Applications A DASE procedural application (PA) is a DASE Application whose initial entity is the specific active object content type application/javatv-xlet. In addition to active object content, a DASE procedural application may contain archive and application defined content as well as other common content types.
DASE System The DASE System interacts with receiver platform services in order to accept input from the broadcast transport and the end-user and generate graphics and audio output for presentation on the receiver platform’s display and audio rendering systems. The receiver platform provides essential services to the DASE System such as operating system services, input/output services, and memory services.
Declarative Application Environment A DASE declarative application environment (DAE) is a logical subsystem of the DASE System which processes markup, stylesheet, and script content. A key component of the declarative application environment is the declarative content decoding engine (DCDE), which takes the form of an XDML parser and a stylesheet and script interpreter.
Procedural Application Environment A DASE procedural application environment (PAE) is a logical subsystem of the DASE System which processes active object content. A key component of the procedural application environment is the procedural content execution engine (PCEE), which, for example, may take the form of a Java Virtual Machine.
The Declarative Application Environment processes declarative applications.
The Procedural Application Environment processes procedural applications. The Java Byte Code Interpreter (a Java Virtual Machine) serves as the Procedural Content Execution Engine and is a part of the Procedural Application Environment. Java Application Programming Interfaces (APIs) provide procedural applications with access to the receiver’s functions.
Common content decoders serve both procedural and declarative application needs for the decoding and presentation of common content types such as PNG, JPEG and Portable Font Resource formats.
iBlast is a nationwide digital distribution network that uses the powerful transmitters of local TV stations to broadcast rich media content directly to home computers, digital set-top boxes, and other receiving devices. Digital media such as movies, movie trailers, games, music and software are broadcast wirelessly to PCs, DTV, STB etc.