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5.5 File-branding guidelines

The file-type brands defined in this specification are used to label 3GP files belonging to Release 7 and conforming to one or more profiles. 3GP files may also conform to earlier Releases or even to other file formats, such as MP4, which is also derived from the ISO base media file format [7].
Table 5.1 contains a non-exhaustive list of examples with 3GP files for various purposes. Note, however, that it only gives typical or suggested uses. Both writers and readers of files should exercise care when using brand identifiers. It is worth repeating the general guidelines here, remembering that a brand identifies a specification or a conformance point in a specification; its presence in a file indicates both:

that the file conforms to the specification; it includes everything required by, and nothing contrary to the specification (though there may be other material);
that a reader implementing that specification (possibly only that specification) is given permission to read and interpret the file.

All 3GP files of Release 5 or later shall contain the compatible brand ‘isom’ indicating that they conform to the ISO base media file format, unless the reader is required to interpret extensions specific to the AVC file format [20], for which case the compatible brand ‘avc1’ shall be used instead (see note 2), or extensions specific to extended presentations (see clause 11), for which case the compatible brand ‘iso2’ shall be used (see note 3). The major brand shall be included in the compatible brands list as well. If a file contains more than one (3GPP) brand in the compatible brands list, the major brand indicates the “best use” of the file. For example, a Release-5 file with audio combined with Timed text is best played by a Release-5 player, but may also be played by a Release-4 player that does not support timed text.

NOTE 1: Since movie fragments are not allowed in Release 4 and Release 5, a fragmented 3GP file should not contain ‘3gp4’ or ‘3gp5’ as brand or compatible brand. A player that does not support movie fragments will only be able to play the first fragment of a fragmented file
NOTE 2: Consider the brands ‘isom’ and ‘avc1’. The first indicates conformance to the base structure of the ISO base media file format (first version) [7]. The second, conformance to the AVC-specific extensions (structures such as sample groups, for example) [20]. A file labelled as ‘isom’ and ‘avc1’ conformant is indicating that either these extensions are not present, or if present, they can be ignored (as an ‘isom’ reader will not understand them). If the writer desires that only readers supporting the extensions read a file, then the ‘isom’ brand would be omitted. These extensions are all optional (i.e. none are required to be in a file, though if they are, an ‘avc1’-conformant reader must interpret them), and therefore a file not using them is still ‘avc1’ conformant.
NOTE 3: The second version of the ISO base media file format [7] defines the brand ‘iso2’ that in addition to ‘isom’ indicates conformance to extensions to the first version.

Table 5.1: Examples of brand usage in 3GP files

Conformance	Suffix	Brand	Compatible brands	Example content
MMS and download: Files shall contain one or more of the brands 3gp4, 3gp5, 3gp6 and 3gp7. It is good practice to include compatible brands of earlier releases to enable legacy players to play the files.
Release 4	.3gp	3gp4	3gp4	H.263 and AMR
Release 5, 4	.3gp	3gp5	3gp5, 3gp4, isom	H.263 and AMR
Release 6, 5, 4	.3gp	3gp6	3gp6, 3gp5, 3gp4, isom	H.263 and AMR
Release 7, 6, 5, 4	.3gp	3gp7	3gp7, 3gp6, 3gp5, 3gp4, isom	H.263 and AMR
Release 6, 5, 4	.3gp	3gp6	3gp6, 3gp5, 3gp4, isom	H.263, AMR and Timed text
Release 6, 5	.3gp	3gp6	3gp6, 3gp5, isom	Timed text
Release 6	.3gp	3gp6	3gp6, isom	H.264 (AVC) and AMR
Release 6	.3gp	3gp6	3gp6, isom	fragmented H.263 and AMR

Progressive download and MMS
Release 6, 5, 4	.3gp	3gr6	3gr6, 3gp6, 3gp5, 3gp4, isom	H.263
Release 6, 5, 4	.3gp	3gr6	3gr6, 3gp6, 3gp5, 3gp4, isom	interleaved H.263 and AMR
Release 6	.3gp	3gr6	3gr6, 3gp6, isom	fragmented and interleaved H.263 and AMR
Release 6	.3gp	3gr6	3gr6, 3gp6, avc1	interleaved H.264 (AVC) and AMR

Streaming servers: Some files may in principle also be used for MMS or download.
Release 6	.3gp	3gs6	3gs6, isom	AMR and hint track
Release 6	.3gp	3gs6	3gs6, isom	2 tracks H.263 and 2 hint tracks
Release 6, 5, 4	.3gp	3gs6	3gs6, 3gp6, 3gp5, 3gp4, isom	H.263, AMR and hint tracks

MBMS extended presentations:
Release 6	.3gp	3ge6	3ge6, iso2	SMIL, AMR and JPEG images

General purpose: Files that are not yet suitable for MMS, download or PSS streaming servers.
Release 6	.3gp	3gg6	3gg6, isom	4 tracks H.263 (and no hint tracks)
Release 6	.3gp	3gg6	3gg6, isom	2 tracks H.263, 3 tracks AMR

3GP file, also conforming to MP4
Release 4, 5 and MP4	.3gp	3gp5	3gp5, 3gp4, mp42, isom	MPEG-4 video

MP4 file, also conforming to 3GP
Release 5 and MP4	.mp4	mp42	mp42, 3gp5, isom	MPEG-4 video and AAC