ISO/IEC 14496-14:2020

Overview

ISO/IEC 14496-14:2020 defines the MP4 file format as a specific instance of the ISO Base Media File format (ISO/IEC 14496-12). This third-edition (2020) standard specifies how MPEG‑4 audio‑visual content and associated metadata are stored, identified and organized in MP4 container files. It covers the mapping of elementary streams, object descriptors, track management, synchronization, and additional MP4-specific boxes and fields used for interchange, editing and streaming workflows.

Key topics and technical requirements

• MP4 as an ISO Media File instance: MP4 inherits the general ISO Base Media File format structure and exercises its full set of features for MPEG‑4 presentations.
• Storage of MPEG‑4 streams: Media data is stored as access units (samples) in their natural, non‑fragmented form to preserve streaming protocol independence and facilitate local editing.
• Elementary stream descriptors (ESDescriptor):
  • ES_ID stored as 0 in the file (track lower‑16 bits used when streamed).
  • streamDependenceFlag set to 0 in-file; dependencies are indicated by track references of type 'dpnd'.
  • URLflag indicates whether the stream is local or referenced externally.
  • SLConfigDescriptor is predefined as type 2 for in-file streams (exceptions when referring to external streams).
• Object descriptors and OD handling: Initial object descriptor and OD tracks are handled specially. For editability, track information is stored in per-track sample descriptions and rewritten when streamed; object descriptor boxes use file-specific descriptors (e.g., ES_ID_Inc).
• Additions to the Base Media Format: MP4 defines specific boxes and fields including the Object Descriptor Box, track reference types, track header box, handler types, MPEG‑4 media header boxes, sample description boxes and degradation priority values.
• Synchronization, composition and hinting: Rules for synchronizing streams, composition of presentations, and handling of hint tracks (for streaming/multiplexing) are specified. Handling of audio timestamps and profile/level indication is covered in Annex A.
• Normative references: ISO/IEC 14496‑12 (Base Media File format) and ISO/IEC 14496‑1 (Systems) are normative prerequisites.

Applications and who uses it

• Media software developers (players, encoders, packagers)
• Streaming service engineers (CDN packaging, hint track generation)
• Content creators and post‑production tools (interchange and editing)
• Device manufacturers implementing MP4 playback/recording
• Archivists and digital preservation teams standardizing stored audiovisual assets

Practical uses include interchange files for editing, creation of hinted presentations for streaming, storing synchronized audio/video tracks with metadata, and ensuring interoperable packaging across platforms.

Related standards

• ISO/IEC 14496‑12 - ISO Base Media File format (normative basis)
• ISO/IEC 14496‑1 - MPEG‑4 Systems (relevant for system-level aspects)

Keywords: MP4 file format, ISO/IEC 14496-14, ISO Base Media File format, MPEG‑4, media container, ESDescriptor, Object Descriptor Box, hint tracks, streaming, sample description.