4 Overview

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

The 3GPP file format (3GP) is defined in this specification as an instance of the ISO base media file format [7]. 3GP is mandated in [8] to be used for continuous media along the entire delivery chain envisaged by the MMS, independent of whether the final delivery is done by streaming or download, thus enhancing interoperability.

In particular, the following stages are considered:

– upload from the originating terminal to the MMS proxy;

– file exchange between MMS servers;

– transfer of the media content to the receiving terminal, either by file download , by streaming or MBMS download delivery [40]. In the first and last case the self-contained file is transferred, whereas in the second case, for RTP streaming, the content is extracted from the file and streamed according to open payload formats. In this case, no trace of the file format remains in the content that goes on the wire/in the air. In segmented streaming over DASH [49], the file is divided into segments for transfer.

For the PSS, the 3GPP file format is mandated in [3] to be used for timed text and it should be supported by PSS servers; 3GP files with streaming-server extensions should be used for storage in streaming servers and the "hint track" mechanism should be used for the preparation for streaming. For Adaptive HTTP Streaming, HTTP streaming extensions are defined.

This specification also defines the necessary structure for integration over several codecs into the ISO base media file format [7]. In particular, this specification defines:

• the necessary structure for integration of 3GPP defined codecs such as AMR, AMR-WB, Enhanced aacPlus and EVS in clauses 6.
• the necessary structure for integration of H.263 video [9] in clause 6.6.