11 Extended presentation format

26.2443GPP3GPP file format (3GP)Release 17Transparent end-to-end Packet-switched Streaming Service (PSS)TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

11.1 General

A 3GP file may include an extended presentation that consists of media files in addition to tracks for audio, video and text. Examples of such media files are static images, e.g. JPEG files, which can be stored in a 3GP "container file". A 3GP container file that includes an extended presentation must include a scene description that governs the rendering of all parts of the 3GP file.

11.2 Storage format

A 3GP file with an extended presentation shall include a Meta box (‘meta’) at the top level of the file as defined in [7]. The Meta box shall include the following boxes:

– Handler box with handler type ‘3gsd’ (3GPP scene description);

– Primary item box or XML box identifying the scene description;

– Item information box;

– Item location box (see below).

A scene description (e.g. an SVG scene, in the case of DIMS, or a SMIL file) shall be included either in an XML box or as an item located by the Item location box. The scene description may refer to both tracks and media files (items).

A 3GP file that contains media files and/or a scene description not stored in an XML box shall include an Item location box locating all contained files and the scene description. Each item corresponding to a media file of the Item location box shall also be included in the Item information box in order to specify its filename (item name) and MIME type. The Item information box shall also include an entry for the scene description that specifies its MIME type. By referring to a Protection scheme information box in the Item protection box, the Item information box can also indicate whether the content of an item is protected (encrypted) as defined in [7] and discussed in clause 10 of the present specification.

11.3 URL forms for items and tracks

All media files and the scene description included in a 3GP file are logically located in the same directory as the 3GP file itself. In general, the Meta box of a 3GP file serve as a container of files that logically "shadow" files outside the 3GP file. See the description of URL forms for Meta boxes in [7] for further details. The Movie box (‘moov’) of a 3GP file contains all media tracks and possible scene description update tracks.

The scene description (primary item) of a 3GP file addresses other resources by using relative URLs. In particular it addresses

– media files (items) by referring to their filenames;

– media tracks by referring to the Movie box with the relative URL "#box=moov".

The default is to address all tracks of the Movie box. However, it is possible to address individual media tracks in the Movie box by referring to their track IDs. The relative URL of a track is defined in terms of ABNF [31] as follows:

relative-track-URL = "#box=moov;track_ID=" track-number* ("," track-number)

track-number = 1*digit

Hence, individual tracks are referenced by listing their numbers, e.g. "#box=moov;track_ID=1,3".

A DIMS (SVG) scene description (primary item) can also address scene updates in a track using the above URL forms. For instance, applying updates to the scene description stored in track 1 after 10 seconds is done as follows:

Note: It is possible to include a 3GP file with tracks as a media file (addressed by filename) rather than using a top-level Movie box for tracks. However, this way the included 3GP file will be "hidden" one layer and interleaving between individual tracks and items less transparent.

11.4 Examples

11.4.1 SMIL presentation

The following example consists of a slide show in SMIL consisting of three images shown with the duration of 3 seconds each and an AMR clip that is played in parallel. The presentation is built from a number of separate files:

– SMIL file: "scene.smil";

– 3GP file with AMR: "audioclip.3gp";

– Image files: "pic1.jpg", "pic2.jpg" and "pic3.jpg".

These files can be packaged into a single 3GP file "presentation.3gp" as an extended presentation. The overall presentation is governed by the SMIL file located as the primary item of "presentation.3gp":

The audio track resides in the Movie box and is referred to as "#box=moov", whereas the images are included as media files in the Meta box.

11.4.2 DIMS presentation

The following example consists of a DIMS presentation that refers to images, an AMR clip and scene updates. The presentation is contained in a single Extended-presentation profile 3GP file containing:

– DIMS scene description (SVG scene) stored as item 1 identified by a Primary item box;

– DIMS updates stored as a DIMS track (track ID 1);

– AMR clip stored as an AMR track (track ID 2);

– Image files: "pic1.jpg", "pic2.jpg" and "pic3.jpg" stored as items 2, 3 and 4.

All references to the DIMS and AMR tracks and the images are made by relative URLs from the DIMS Unit in the primary item:

An Item information box specifies the MIME type of the scene description (SVG scene) and the filenames and MIME types of the image files. An Item location box specifies the locations of all items.