ISO IEC 14496-15-2024 PDF

Full title and description

St ISO/IEC 14496-15:2024 — Information technology — Coding of audio-visual objects — Part 15: Carriage of timed text and other data in ISOBMFF (2024 version). This standard specifies formats and mechanisms for carrying timed text (subtitles, captions, and related data) and auxiliary data (such as event messages and media-related metadata) in ISOBMFF (ISO Base Media File Format) containers, ensuring interoperability for timed text interchange, synchronization, and presentation in MPEG-4 systems and related applications.

Abstract

ISO/IEC 14496-15:2024 defines a set of standardized sample entry formats, box structures, and metadata constructs for embedding and transporting timed text and related data within ISO Base Media File Format (ISOBMFF) files. It covers the representation of text streams, style and layout information, timing and synchronization, and associated event/message constructs, as well as registration and signalling mechanisms to enable consistent playback across platforms and devices. The 2024 edition updates and clarifies mappings, encodings, and interoperability behaviors to reflect current industry practice.

General information

• Status: Published standard (2024 edition)
• Publication date: 2024
• Publisher: ISO/IEC (Joint technical committee ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information)
• ICS / categories: 35.240.60 (Digital compression and cryptography for audiovisual systems), 33.180 (Multimedia)
• Edition / version: 2024 edition (latest revision of Part 15)
• Number of pages: Typically 30–80 pages (varies by published format); exact pagination for the 2024 PDF edition may vary

Scope

This part of ISO/IEC 14496 specifies the methods for carriage of timed text and associated data in the ISO Base Media File Format (ISOBMFF). It defines box (atom) structures, sample entry types, codecs and track signalling for subtitle/caption streams and auxiliary timed data, the mapping of text and styling formats into ISOBMFF, timing/sync rules relative to media tracks, and provisions for event messages and metadata. The scope includes interoperability considerations, backward-compatible registrations, and guidance for authoring and player implementations to ensure consistent handling of text presentation, language and track selection, and timed events.

Key topics and requirements

• Definitions of ISOBMFF sample entry types and box structures for timed text and data tracks.
• Mappings for common text formats (including text encodings and styling) into ISOBMFF containers.
• Timing and synchronization rules to align timed text with audio/video tracks and presentation timelines.
• Specification of event/message boxes for in-band signalling (e.g., timed metadata, captions, SCTE-like events).
• Language tagging, track selection semantics, and metadata for accessibility (captions, subtitles, descriptions).
• Interoperability and backward compatibility requirements for players, packagers and editors.
• Registration and signalling of custom timed data types while preserving conformance to the standard.

Typical use and users

The standard is used by multimedia system designers, media packagers, content authors, streaming service operators, player and device implementers, and accessibility tool developers. Typical tasks include multiplexing subtitles and captions into MP4/DASH/HLS origin files, authoring timed text tracks with styling and layout, implementing ISOBMFF parsers and renderers, and ensuring interoperable delivery of captions, subtitles, and timed metadata across platforms and devices.

Related standards

ISO/IEC 14496-15 is part of the MPEG-4 suite (ISO/IEC 14496). Closely related standards include other parts of ISO/IEC 14496 (container, systems and codecs), the ISO Base Media File Format (ISO/IEC 14496-12), specifications for timed text formats (such as TTML and WebVTT mappings), MPEG-DASH (for streaming use cases), and accessibility-related guidance from relevant organizations. Implementers frequently reference container and codec parts of ISO/IEC 14496 and ISOBMFF registration registries for interoperability.

Keywords

ISOBMFF, MP4, timed text, subtitles, captions, event messages, timed metadata, sample entry, box, atom, synchronization, accessibility, MPEG-4 Part 15, 14496-15

FAQ

Q: What is this standard?

A: ISO/IEC 14496-15:2024 (MPEG-4 Part 15) specifies how timed text and other timed data are carried inside ISO Base Media File Format containers, defining sample entries, box structures, timing and synchronization, and related metadata to ensure interoperable subtitle, caption and event handling.

Q: What does it cover?

A: It covers the structural and semantic rules for embedding text tracks and auxiliary timed data within ISOBMFF files, including format mappings, encoding and styling support, timing alignment with media tracks, event/message constructs, language and accessibility signalling, and registration of data types.

Q: Who typically uses it?

A: Media packagers, streaming service engineers, content authors, player developers, broadcast and OTT system integrators, and accessibility specialists use this standard to author, package and play back subtitles, captions and timed metadata consistently.

Q: Is it current or superseded?

A: The entry here refers to the 2024 edition; this is the current edition of Part 15 as of 2024. Users should confirm with the official standards body for any later amendments or corrigenda.

Q: Is it part of a series?

A: Yes. It is Part 15 of ISO/IEC 14496 (the MPEG-4 family). Other parts cover systems, container format, audio and video codec specifications, and related functionality.

Q: What are the key keywords?

A: ISOBMFF, timed text, subtitles, captions, event messages, timed metadata, MP4, sample entry, box, synchronization, accessibility.