ISO/IEC 14496-32:2025

International
Standard
ISO/IEC 14496-32
Second edition
Information technology — Coding of
2025-04
audio-visual objects —
Part 32:
File format reference software and
conformance
Reference number
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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Published in Switzerland
© ISO/IEC 2025 – All rights reserved
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference software . 1
5 Conformance . 2
5.1 Overview .2
5.2 Standard specific considerations .2
5.2.1 Considerations for ISO/IEC 14496-30 .2
5.3 File documentation .3
5.3.1 Files from related conformance programs .3
5.3.2 Files unique to this conformance program .4
Bibliography .23

© ISO/IEC 2025 – All rights reserved
iii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not
received notice of (a) patent(s) which may be required to implement this document. However, implementers
are cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held
responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This second edition cancels and replaces the first edition (ISO/IEC 14496-32:2021), which has been
technically revised.
The main changes are as follows:
— new conformance files have been added to the conformance suite with additional documentation in
Clause 5;
— obsolete spreadsheets and html files have been removed.
A list of all parts in the ISO/IEC 14496 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.

© ISO/IEC 2025 – All rights reserved
iv
International Standard ISO/IEC 14496-32:2025(en)
Information technology — Coding of audio-visual objects —
Part 32:
File format reference software and conformance
1 Scope
This document describes the reference software and conformance suite for the file format documents
in multiple standards. Since these standards share a lot of technology, their reference software and
conformance program are being handled together. These standards are: ISO/IEC 14496-12, ISO/IEC 14496-14,
ISO/IEC 14496-15, ISO/IEC 14496-30 and ISO/IEC 23008-12.
The purpose of the conformance suite is to cover the set of valid features that can be exercised in the file
format. Media conformance is not covered, though of course to exercise the file format features, media will
be stored.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 14496-12, Information technology — Coding of audio-visual objects — Part 12: ISO base media file format
ISO/IEC 14496-14, Information technology — Coding of audio-visual objects — Part 14: MP4 file format
ISO/IEC 14496-15, Information technology — Coding of audio-visual objects — Part 15: Carriage of network
abstraction layer (NAL) unit structured video in the ISO base media file format
ISO/IEC 14496-30, Information technology — Coding of audio-visual objects — Part 30: Timed text and other
visual overlays in ISO base media file format
ISO/IEC 23008-12, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 12: Image File Format
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 14496-12, ISO/IEC 14496-14,
ISO/IEC 14496-15, ISO/IEC 14496-30 and ISO/IEC 23008-12 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Reference software
The reference software for ISO/IEC 14496-12, ISO/IEC 14496-14, ISO/IEC 14496-15, ISO/IEC 14496-30, and
ISO/IEC 23008-12 is available at: http:// standards .iso .org/ iso -iec/ 14496/ -32/ ed -2/ en/ reference _software/

© ISO/IEC 2025 – All rights reserved
This link contains version v.0.3.0 of the software with the changelog included in the software package, which
documents new features compared to older versions.
5 Conformance
5.1 Overview
The conformance suite for ISO/IEC 14496-12, ISO/IEC 14496-14, ISO/IEC 14496-15, ISO/IEC 14496-30 and
ISO/IEC 23008-12 is provided at: http:// standards .iso .org/ iso -iec/ 14496/ -32/ ed -2/ en/ conformance/
The suite of conformance tests does not currently cover deliberately errored files. However, such files do
occur in practice and implementations should be written to be resilient.
There is no official reference tool provided to check the conformance of files. However, such tools do exist.
The reference software can be used to open files in ‘debug’ mode and provide a listing of what it finds, and
other trade associations and standards bodies might have validation tools tailored to their areas.
5.2 Standard specific considerations
5.2.1 Considerations for ISO/IEC 14496-30
Two files are proposed regarding:
— WebVTT;
— TTML.
There are several general features of ISO/IEC 14496-30 which are not exercised in the above files, specifically:
— a track with 'mul' language;
— a track sharing resources (images, …) between samples through the use of a MetaBox;
— file with a subtitle and a font track.
There are several features specific to the carriage of TTML in MP4 which are not exercised:
— timing:
— ‘empty’ sample;
— sample with a document containing a larger time range than the sample presentation range;
— sample with a document whose time range is smaller than the sample range;
— sample entry format:
— with multiple namespace values;
— with schema location;
— with auxiliary mime types;
— sample format:
— with additional resources.
© ISO/IEC 2025 – All rights reserved
5.3 File documentation
5.3.1 Files from related conformance programs
5.3.1.1 Overview
Some files provided in this suite originate from external conformance programs, from other ISO documents
or external specifications. The latest version should be obtained from their original source as indicated in
the following sections.
5.3.1.2 Audio-based conformance files
ISO/IEC 14496-26 provides several MP4 files containing MPEG-4 AAC, MPEG-D MPS, and MPEG-D USAC
streams and exercising features of the ISOBMFF. Within these files, only some are necessary to cover all the
ISOBMFF features. These files are from the “AAC-Conformance” part. The features specifically exercised by
these files compared to existing files are: 'padb' and 'm4ae'.
The following files are also included for ISOBMFF conformance:
— ./mpeg-audio-conformance/aac-conformance/ac01.mp4 ('padb')
— ./mpeg-audio-conformance/aac-conformance/sls2100_aot02_048_16.mp4 ('m4ae')
Original files can be obtained from ISO/IEC 14496-26.
5.3.1.3 Timed text conformance files
DECE produced a set of Timed Text test vector files with video and audio tracks. Some of these files exercise
features of ISO/IEC 14496-12 and ISO/IEC 14496-30. The following files are added as part of ISOBMFF
conformance:
— Solekai002_1280_23_1x1_v7clear.uvu
— Solekai007_1920_29_1x1_v7clear.uvu
Original files can be obtained from https:// www .uvcentral .com/ cff/ cff -test -files .html.
5.3.1.4 DASH-based conformance files
The ISO/IEC 23009 series specifies the use of ISOBMFF files for adaptive streaming. ISO/IEC 23009-2
contains the following files that exercise specific features of the ISOBMFF:
— ./green/video_2500000bps_0.mp4
— ./green/meta_2500000bps_0.mp4m
— ./nalu/svc/mp4-onDemand-LastTime-depRep.mp4
— ./nalu/mvc/DDF_10s_25fps.mp4
Original files can be obtained from https:// testassets .dashif .org/ .
5.3.1.5 MAF-based conformance files
The ISO/IEC 23000 series uses the ISOBMFF standard at its core and contains some files (related to the PAAF
and VSAF standards). None of these files exercise new features, but they exercise some features differently.
The following files are copied in this ISOBMFF conformance:
— ./maf/vsaf/1.mp4
— ./maf/paaf/01_output_a.paf
© ISO/IEC 2025 – All rights reserved
Original files can be obtained from ISO/IEC 23000-6 and ISO/IEC 23000-10.
5.3.2 Files unique to this conformance program
5.3.2.1 a1-foreman-QCIF.mp4
This file is very simple. It has an MPEG-4 video part 2 visual track, and an AAC track, interleaved; and a
minimal BIFS scene and OD track, with an IOD.
5.3.2.2 a2-foreman-QCIF-hinted.mp4
This file is basically the same as a1-foreman-QCIF.mp4 but hinted for RTP transmission.
5.3.2.3 a3-tone-protected.mp4
This file uses the protected stream structures. The keys are also supplied (a3c-prot-keys.txt), and the result
of de-protection (a3b-tone-deprot.mp4, for comparison).
5.3.2.4 a4-tone-fragmented.mp4
This file uses movie fragments. The initial 1-second movie is followed by a 1-second movie fragment.
Fragment-aware readers should play 2 second of content, fragment-unaware readers only 1 second.
5.3.2.5 a5-foreman-AVC.mp4
This is a very simple video-only main profile AVC file. Since it is main profile, composition offsets are used.
5.3.2.6 a6_tone_multifile.mp4
This is the same tone as used in test a4-tone-fragmented.mp4, but the actual access units are stored in a
separate file, referenced by a relative URL “./myData.dat” from the main file.
5.3.2.7 a7-tone-oddities.mp4
This file also uses the 1-second tone. However, it has:
— a UUID,
— a non-standard 'junk' atom in it (which should be ignored),
— a free space box (which should also be ignored),
— the compact sample size table,
— a padding bits table (though the padding bits are all set to zero).
The 'mdat' atom has an implied length (the length in the file is zero, meaning to end of file).
5.3.2.8 a8-foreman_QCIF_edit.mp4
This file has the “foreman” 10 second of video, with 5 seconds before and after, of the “container” video.
However, the edit list should select only foreman. The container ship should not appear. Note that the
I-frames do not land on the edit boundaries. A player will have to pre-roll the video from an I-frame to work
correctly.
5.3.2.9 a9-aac-samplegroups-edit.mp4
This file demonstrates the suggested way of handling AAC: it has a pre-roll sample group, and a track edit
that is not aligned at either start or end with an AAC sample boundary.

© ISO/IEC 2025 – All rights reserved
5.3.2.10 a10-foreman_QCIF-raw.mp4
This file contains ‘raw’ (YUV420) video. Since this is an unregistered codec type (it is supported in QuickTime
movie files) this is an unrecognized codec type from an ISOBMFF reader’s point of view.
5.3.2.11 LargerThan4GB.mp4
This file tests handling of very large (> 4GB) files.
The 'mdat' atom has a large (64-bit) size, and all the samples are at the end, preceded by 4 GB of zeroes.
Therefore, the chunk offset table is also a 'co64', not a 'stco'. The actual media data is a simple AAC tone.
5.3.2.12 f1.mp4
This file is a simple AVC + AAC file. It has an MPEG-4 AVC Baseline visual track (including the optional
BitrateBox), and an AAC track.
5.3.2.13 f2.mp4
This file is a protected AVC + AAC file. The 128-bit key for the decryption process is 0x010203040506
07080102030405060708 for both tracks. The salt (counter offset) is 0x0000000000000001 for the audio and
0x0000000000000002. Because of the usage of protected streams, 'isom' was replaced with 'iso2' in the list
of compatible brands.
5.3.2.14 male_amr122.3gp
This file and the following 3GP files contain AMR speech at 12.2 or 6.7 kbps, with or without DTX (silence
frames). In addition, 3GP files with hint tracks are provided.
AMR 12.2 kbps, no DTX
5.3.2.15 male_amr122DTX.3gp
AMR 12.2 kbps, DTX
5.3.2.16 female_amr67_hinted.3gp
AMR 6.7 kbps, no DTX, hint track
5.3.2.17 female_amr67DTX_hinted.3gp
AMR 6.7 kbps, DTX, hint track
5.3.2.18 pdin_example.3gp
This file contains one video track with AVC and a progressive download information box specifying required
initial delays for six different download rates. The download rates 5106, 7659, 10213, 12766, 15319 and
20426 bytes per second require initial delays of 20808, 7206, 1089, 652, 396 and 200 seconds, respectively.
5.3.2.19 rs_example_r1.3gp
This file contains three video tracks with AVC at different bitrates, three audio tracks with HE-AACv2 at
different bitrates, track selection box, and rate share information with two operation points. For the first
operation point (100 kilobits per second), the target rate shares are 20 % for audio and 80 % for video. For
the second operation point (160 kilobits per second), the target rate share weights are 20 and 140 for audio
and video, respectively. As the sum is not 100 for the second case, the numbers correspond to weights that
need to be normalized by the server/player. Depending on the available bitrate, the server selects which
tracks to stream/play.
© ISO/IEC 2025 – All rights reserved
5.3.2.20 01_simple.mp4
Simple AV file (MPEG-4 ASP video, AAC audio), BIFS + OD scene, 2 timelines (BIFS/OD and A/V), interleaved.
5.3.2.21 02_dref_edts_img.mp4
Image track, audio track with edit list, with media data located outside the file.
5.3.2.22 03_hinted.mp4
Simple video file with MPEG-4 ASP visual, hinted for RTP (RFC 3640 payload).
5.3.2.23 04_bifs_video.mp4
Video (MPEG-4 ASP visual) + BIFS text (reading 'unprotected video'), with a single timeline.
5.3.2.24 05_bifs_video_protected_v2.mp4
Protected video (MPEG-4 ASP visual) + BIFS text (reading 'protected video'), with a single timeline. Keys are
described in an item located in a 'meta' box at the file root level, ISMA KMS URI referring to this item. Keys are:
— key 0x2b7e151628aed2a6abf7158809cf4f3c
— salt 0xf8f9fafbfcfdfeff
Only I-frames of the video track are encrypted.
5.3.2.25 06_bifs.mp4
Simple animation with a single BIFS track. File 'moov' box is located after 'mdat' box.
5.3.2.26 07_bifs_sprite.mp4
Simple looping animation with two BIFS tracks, exercising decoding dependency and synchronization track
references.
Animation track uses ShadowSync samples in-between regular samples.
5.3.2.27 08_bifs_carousel_v2.mp4
Simple animation with a single BIFS track. Random access samples are inserted in-between the samples for
the BIFS carrousel and signalled with a sample dependency type box.
5.3.2.28 09_text.mp4
Sample MPEG-4 streaming text file, stored in 3GPP text track format, with 2 sample descriptions.
5.3.2.29 10_fragments.mp4
Simple AV file (MPEG-4 ASP video, AAC audio), BIFS + OD scene, stored as a sequence of 500 ms fragments.
5.3.2.30 12_metas.mp4
File with a single image track, containing 3 'meta' boxes (file, movie and track level). Meta at movie level has
an item referencing the entire file.

© ISO/IEC 2025 – All rights reserved
5.3.2.31 13_long.mp4
Long duration file, with MPEG-4 ASP track (only I-frames present). Total file duration is 5000000000 seconds
(158 Years 81 Days 08:53:20).
5.3.2.32 14_large.mp4
Large file exercising 64 bits chunk offset.
5.3.2.33 16_vtt.mp4
The file 16_vtt.mp4 contains the following boxes:
— wvtt
— vttC
— vttc
— ctim
— iden
— sttg
— payl
— vtte
— vtta
5.3.2.34 17_negative_ctso.mp4
This file contains a single AVC video track with a ctts box using version 1. The box declares negative
composition offset such that the offset of the first frame is 0.
5.3.2.35 18_pssh_v2.mp4
This file contains an encrypted video track. The file also contains 2 pssh boxes: one with only opaque data
and the other one with KID information.
5.3.2.36 19_ttml.mp4
This file contains a simple TTML track.
5.3.2.37 20_stxt.mp4
This file contains a track of type 'stxt' whose content is SVG, the mime type is image/svg+xml. The SVG
content is distributed over 4 samples. The configuration of the track contains the header of the SVG content.
5.3.2.38 21_segment.mp4
This file contains a self-initializing DASH media segment with the following boxes: 'sdix', 'prft', trun v1, sgpd.
5.3.2.39 22_tx3g.mp4
The file provides a simple 3GPP Timed Text stream stored in an mp4 file.

© ISO/IEC 2025 – All rights reserved
5.3.2.40 compact-no-code-fec-1.iso3
This file contains one JPEG file stored as an item. Compact No-Code FEC is used, and the file is partitioned
into one source block. The file contains also one hint track for FLUTE transmission.
5.3.2.41 compact-no-code-fec-2.iso3
This file contains one JPEG file stored as items. Compact No-Code FEC is used, and the file is partitioned into
three source blocks. The file contains also one hint track for FLUTE transmission.
5.3.2.42 mbms-fec.iso3
This file contains two JPEG files stored as items. MBMS-FEC is used and both files are partitioned into one
source block and several sub-blocks. Parity symbols for the source block are stored as an FEC reservoir item.
The file contains also three hint tracks for FLUTE transmission with FEC overheads 10 %, 20 % and 40 %.
Each hint track defines transmission of both JPEG files over one FLUTE channel.
5.3.2.43 fragment-random-access-1+AF8-rev1.mp4
This uses movie fragment random access boxes (movie fragment random access, track fragment random
access, movie fragment random access offset in ISO/IEC 14496-12). These boxes help readers to search
where random access points are.
There are random access points at 1-second interval.
For the purpose of reference, the initial 1-second movie is followed by a 14-second movie fragment. The
movie consists of audio and video tracks. Fragment aware readers should play 15.3 seconds of content,
fragment-unaware readers only 1 second.
5.3.2.44 fragment-random-access-2.mp4
This file uses movie fragment random access boxes as 5.3.2.43. However, there are random access points
at 5-second interval. For reference, the initial 1-second movie is followed by a 10.1-second movie fragment.
The movie consists of audio and video tracks. Fragment aware readers should play 15.1 seconds of content,
fragment-unaware readers only 5 seconds.
5.3.2.45 timed-metadata.mp4
Simple audio file with a timed-metadata track.
5.3.2.46 restricted.mp4
Post-decoder requirements on media with the 'resv', 'rinf', 'stvi', and 'schi' boxes.
This bitstream exercises the method of restricting access to video media. The media itself is in stereoscopic
3D format with side-by-side frame packing.
5.3.2.47 sg-tl-st.mp4
— Level assignment 'leva' box
— Sub-tracks
— strk box
— stri box
— strd box
© ISO/IEC 2025 – All rights reserved
— stsg box
— Segment index box sidx box
— Sub-segment index ssix box
— Temporal level sample group within sgpd and sbgp boxes.
This bitstream exercises a method of splitting video media data such that it can be efficiently transmitted,
decoded, and played back at full framerate or half framerate.
The first M samples in the mdat box (sample group 1) give an independently decodable media segment, and
the remaining samples (sample group 2) are not referenced by any samples in group 1.
Sample groups 1 and 2 are assigned to temporal levels 1 and 2 respectively. Each level is referenced as a
byte range in the sub-segment index. Two sub-tracks are defined, the first of which applies only to sample
group 1, and the second of which applies to the full range of samples.
5.3.2.48 subs_tile_hvc1.mp4
This file contains a hvc1 sample entry HEVC video track with associated tile-based sub-sample (flags=2).
The sub-sample information box (subs) is used to provide information such as sub-sample sizes in bytes,
priority, etc. without having to decode HEVC data. The sub-samples are derived by using entry point offsets
found from the HEVC slice header. The values of discardable and subsample_priority fields in the subs box
are set to 0 and the field subsample_size is set to the entry point offset value.
5.3.2.49 subs_slice_hvc1.mp4
The file contains a hvc1 sample entry HEVC video track with associated slice-based sub-sample (flags=4).
The sub-sample information box (subs) is constructed by using the sizes of the slices. The values of
discardable and subsample_priority fields in the subs box are set to 0 and the field subsample_size is set to
the slice size in bytes.
5.3.2.50 aggr_hvc1.mp4
Aggregators inside the file:
— Aggregator container in the HEVC bit stream
— Aggregates SHVC enhancement layer
This file includes an aggregator container around SHVC enhancement layer NAL units so that the video can
be viewed and decoded as normal HEVC. Decoder supporting aggregators can increase video resolution by
extracting the enhancement layer. Aggregator is a special type of NAL unit including or referring to a set of
data. In this coded bit stream, the aggregator includes the aggregated data.
5.3.2.51 trgr_hvc1.mp4
This bit stream includes a track group box (trgr) that groups related tracks together and a hvc1 sample
entry that contains the HEVC video configurations.
5.3.2.52 alst_hvc1.mp4
The alternative startup sequences sample group (alst) is indicated by two parameters: roll_count and
first_output_sample, which specify the number of samples in the group and the first sample in the sequence
to be sent to the output, respectively. In addition, the random access point (RAP) sample group ('rap ') is
used to point the location of the sync samples where alst sample group could be found in the stream. The
RAP sample group is composed of CRA/BLA/IDR/IRAP pictures. A position in the stream is sought among
the RAP samples preceding the position of interest. If the selected sample also belongs to the alst sample
group, alternative startup sequence is activated. With roll_count=2 and first_output_sample=1, S is
© ISO/IEC 2025 – All rights reserved
sent to a decoder, S .S are skipped, and S is sent to a decoder after which alternative startup sequence is
1 7 8
complete and the decoding continues normally.
5.3.2.53 rtp_rtcp_reception_hint_tracks_v2.mp4
— RTP Reception Hint Track sample entry rrtp
— Timescale entry box tims
— Time offset box tsro
— Timestamp Synchrony box tssy
— RTP Track SDP Hint Information box 'sdp '
— RTCP Reception Hint Track sample entry rtcp
— Track Reference Type Box: Content description cdsc
— RTP movie information box 'rtp '
— Hint media header (in RTP reception hint tracks) hmhd
— Null media header box (in RTCP reception hint tracks) nmhd
This file contains two media tracks, two RTP Reception Hint Tracks, and two RTCP Reception Hint Tracks. The
file is composed of Received RTP Hint Sample Entry box (rrtp) for the RTP Reception Hint Track description,
timescale entry box (tims) for timescale, time offset box (tsro) for first sample RTP timestamp offset, and
timestamp synchrony box (tssy) for signalling whether a track has been synchronized during recording.
timestamp_sync field has been set to 1 indicating no synchronization was done during recording. Both
RTP Reception Hint Tracks also have an RTP Track SDP Hint Information box ('sdp ') containing a media
description part of an SDP message. The RTCP reception Hint Tracks are described by Received RTCP Hint
Sample Entry box (rtcp). In addition, RTCP tracks have a Content Description box (cdsc)
...