10. The SMIL 2.1 Timing and Synchronization Module Updates

Editor for SMIL 2.1

Dick Bulterman, CWI/Amsterdam

Editors for SMIL 2.0:

Patrick Schmitz, Microsoft

Jeff Ayars, RealNetworks

Bridie Saccocio, RealNetworks

Muriel Jourdan, INRIA.

10.1 Overview and Summary of Changes for SMIL 2.1

This section is informative

The SMIL 2.1 specification leaves the basic syntax and semantics of the SMIL 2.0 timing model unchanged [SMIL20-timing]. The only change for SMIL 2.1 that SMIL 2.0's ExclTimeContainers module is deprecated and replaced with two new modules: BasicExclTimeContainers and BasicPriorityClassContainers. This partitioning is done to reduce the implementation burden of the excl element on low-powered devices or in implementations in which the full functionality of the priority class mechanism of SMIL 2.0 is not required.

The following sections will highlight any text changes to the SMIL 2.0 timing and synchronization specification [SMIL20-timing]. Where no changes have been made, this is explicitly noted.

As a result of this change, SMIL 2.1 Timing and Synchronization support is broken down into 16 modules instead of the 15 modules used in SMIL 2.0. These modules are described in Appendix A: SMIL Timing and Synchronization modules.

Note: A SMIL 2.0 errata was raised which affects SMIL 2.1 Timing and Synchronization Module Update . Please refer to the SMIL 2.0 [Second Edition] Errata page, for details. This errata should be incorporated in the next SMIL 2.1 Proposed Recommendation full version.

10.2 Introduction

This section remains unchanged.

10.3 Overview of SMIL timing

This section remains unchanged.

10.4 Language definition

The majority of this section remains unchanged for SMIL 2.1 except for the description of the behavior of the excl element.

10.4.1 Attributes

This sub-section remains unchanged.

10.4.2 Elements

The definitions of the par, seq, and priorityClass elements in the SMIL 2.0 specification remain unchanged in SMIL 2.1. The only change made in this section is the definition of the excl element.

The excl element

SMIL 2.1 modifies the definition of the SMIL 2.0 exclusive container, excl. The modification provides default behavior for implementations that only support the exclusive element and not the priorityClass element.

This section provides all of the normative text of the exclusive element definition. For examples and use cases, please refer to the SMIL 2.0 specification [SMIL20-timing].

This section is normative

excl

This defines a time container with semantics based upon par, but with the additional constraint that only one child element may play at any given time. If any element begins playing while another is already playing, the element that was playing is stopped. If the priorityClass element is also supported by a profile, child elements in an excl container may be grouped into categories; the behavior of the element that was playing at the time a new element starts can be defined to have stop/pause/interruption behavior. The priorityClass can define several levels of interrupt behavior (one per class), each of which can be controlled explicitly.

Implicit duration of excl containers

This section is normative

• The implicit duration of an excl container is defined the same as for a par container, using the endsync="last" semantics. However, since the default timing for children of excl is interactive, the implicit duration for excl time containers with only default timing on the children will be 0.

The remainder of this section remains unchanged.

10.4.3 Semantics of the Timing Model

This sub-section remains unchanged.

10.4.4 Clarifications and surprising results

This sub-section remains unchanged.

10.5 Integrating SMIL Timing and Synchronization into a host language

This section remains unchanged.

10.6 Document object model support

This sub-section remains unchanged.

10.7 Glossary

This sub-section remains unchanged.

10.8 Appendix A: SMIL Timing and Synchronization modules

This section is normative.

All SMIL 2.0 timing and synchronization modules remain unchanged except as noted in this section.

ExclTimeContainers

This module is depreciated in SMIL 2.1.

BasicExclTimeContainers

This module is new to SMIL 2.1. It includes a time container that defines a mutually exclusive set of elements and describes the 'stop' interrupt semantic among these elements.

Module dependencies

None.

Included features

excl element, fill and endsync attributes.

Other module specific integration requirements

fill="transition" is only supported when BasicTransitions or InlineTransitions is included in the language profile. If FillDefault is not included in the profile, fill="default" is interpreted the same as fill="auto".

BasicPriorityClassContainers

This module is new to SMIL 2.1. It includes a child element for the excl that is used to describe interrupt semantics among group of children of the the exclusive element.

Module dependencies

The BasicExclTimeContiners module must be included in a profile containing the BasicPriorityClassContainers module

Included features

priorityClass element.

Other module specific integration requirements

None.

10.9 Appendix B: Annotated examples

This sub-section remains unchanged.

10.10 Appendix C: Differences from SMIL 1.0

This sub-section remains unchanged.

10.11 Appendix D: Unifying event based and scheduled timing

This sub-section remains unchanged.