ISO/IEC 14496-32:2025

Overview

ISO/IEC 14496-32:2025 - "Information technology - Coding of audio‑visual objects - Part 32: File format reference software and conformance" defines the reference software and conformance suite for the family of ISO Base Media File Format (ISOBMFF) based file format standards. It consolidates the conformance program for multiple related parts that share common file format technology and provides test vectors, documentation and reference implementations to exercise valid file format features. The standard focuses on file-format conformance (not media codec conformance) and supplies reference software and a test suite hosted on the ISO website.

Key topics

• Reference software distribution: A reference implementation (version v.0.3.0 in the published package) is published by ISO to help implementers parse and debug ISOBMFF files.
• Conformance suite: A curated set of test files and documentation that exercise valid file‑format features across related standards; the suite is available from ISO and links to files from other conformance programs when relevant.
• Scope limitations: The suite covers file format features only - media conformance (codec bitstream correctness) is outside its scope, though media is included to exercise containers.
• Test coverage and examples: Includes simple AV files, hinted RTP files, protected/fragmented files, large‑file (>4 GB) tests (e.g., LargerThan4GB.mp4), raw/unregistered codec samples, Timed Text vectors (WebVTT and TTML), AMR/3GP examples, and DASH/MAF derived test files.
• Conformance considerations: Notes on features not currently exercised (e.g., specific TTML carriage cases, track language 'mul', shared MetaBox resources), guidance on using reference software in debug mode, and the absence of deliberately malformed test vectors in the suite.
• Maintenance notes: This second edition adds new conformance files and removes obsolete spreadsheets/html artifacts.

Applications

ISO/IEC 14496-32:2025 is practical for:

• File format implementers - developers building ISOBMFF/MP4 parsers, muxers and editors.
• Player and streaming vendors - ensuring correct handling of container features such as edit lists, fragments, hint tracks and large file offsets.
• Test labs and QA teams - using reference files to validate file-level conformance and robustness.
• Standards bodies and integrators - aligning conformance programs across MP4, timed text (TTML/WebVTT) and related specifications.
• Content delivery and CDN engineers - verifying packaging behaviors for adaptive streaming and progressive download scenarios.

Who should use it: codec integrators, media‑player developers, QA/test engineers, standards implementers and researchers working with MP4/ISOBMFF.

Related standards

This part is explicitly linked to:

• ISO/IEC 14496-12 (ISO base media file format)
• ISO/IEC 14496-14 (MP4 file format)
• ISO/IEC 14496-15 (NAL unit carriage in ISOBMFF)
• ISO/IEC 14496-30 (Timed text and overlays in ISOBMFF)
• ISO/IEC 23008-12 (Image File Format)

Keywords: ISO/IEC 14496-32:2025, ISOBMFF, MP4 conformance, file format reference software, MP4 test suite, TTML, WebVTT, AAC, AVC, 3GP, conformance testing.