ISO/IEC 14496-20:20 08分别定义了一种场景描述格式（LASeR）和一种聚合格式（SAF），它们适用于向诸如移动电话的资源受限设备表示和传递富媒体服务。LASeR旨在在场景描述级别满足富媒体服务的所有要求。LASeR支持:从SVG继承的一组优化的对象来描述富媒体场景，SVG上的一小组关键兼容扩展，编码和传输激光流然后重建SVG内容的能力，动态更新场景以实现响应、平滑和连续的服务，简单而有效的压缩以改善交付和解析时间以及存储大小，设计目标之一是允许直接实现所记录的SDL，以及符合ISO/IEC 23001-1解码激光比特流，与具有帧精确同步的音频和视频流的高效接口，使用任何字体格式，包括OpenType行业标准，以及从其他流行的富媒体格式轻松转换，以便利用现有内容和开发人员社区。激光的技术选择标准包括压缩效率，但也包括代码和内存占用以及性能。其他目标包括:可伸缩性、对用户环境的适应性、格式的可扩展性、定义小概要的能力、J2ME实现的可行性、错误恢复和实现的安全性。SAF旨在在媒体/场景描述和现有传输协议之间的接口上满足富媒体服务的所有要求:任何类型的流的简单聚合、MPEG和非MPEG流、针对带宽有限的网络优化的数据包报头、轻松映射到流行的流格式、缓存管理功能和可扩展性。SAF旨在补充LASeR提供简单的交互式服务，带来:高效和动态的打包，以极低的开销应对高延迟网络、媒体交织和同步支持。ISO/IEC 14496-20:20 08定义了SAF用于激光内容；然而，激光可以独立于SAF使用。

ISO/IEC 14496-20:2008 defines a scene description format (LASeR) and an aggregation format (SAF) respectively suitable for representing and delivering rich-media services to resource-constrained devices such as mobile phones.

LASeR aims at fulfilling all the requirements of rich-media services at the scene description level. LASeR supports:

• an optimized set of objects inherited from SVG to describe rich-media scenes,


• a small set of key compatible extensions over SVG,


• the ability to encode and transmit a LASeR stream and then reconstruct SVG content,


• dynamic updating of the scene to achieve a reactive, smooth and continuous service,


• simple yet efficient compression to improve delivery and parsing times, as well as storage size, one of the design goals being to allow both for a direct implementation of the SDL as documented, as well as for a decoder compliant with ISO/IEC 23001-1 to decode the LASeR bitstream,


• an efficient interface with audio and visual streams with frame-accurate synchronization,


• use of any font format, including the OpenType industry standard, and


• easy conversion from other popular rich-media formats in order to leverage existing content and developer communities.

Technology selection criteria for LASeR included compression efficiency, but also code and memory footprint and performance. Other aims included: scalability, adaptability to the user context, extensibility of the format, ability to define small profiles, feasibility of a J2ME implementation, error resilience and safety of implementations.

SAF aims at fulfilling all the requirements of rich-media services at the interface between media/scene description and existing transport protocols:

• simple aggregation of any type of stream,


• signaling of MPEG and non-MPEG streams,


• optimized packet headers for bandwidth-limited networks,


• easy mapping to popular streaming formats,


• cache management capability, and


• extensibility.

SAF has been designed to complement LASeR for simple, interactive services, bringing:

• efficient and dynamic packaging to cope with high latency networks,


• media interleaving, and


• synchronization support with a very low overhead.

ISO/IEC 14496-20:2008 defines the usage of SAF for LASeR content; however, LASeR can be used independently from SAF.