Network Working Group R. Castagno Request for Comments: 3839 Nokia Mobile Phones Category: Standards Track D. Singer Apple Computer, Inc. July 2004
MIME Type Registrations for 3rd Generation Partnership Project (3GPP) Multimedia files
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document serves to register and document the standard MIME types associated with the 3GPP multimedia file format, which is part of the family based on the ISO Media File Format.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119].
The third-generation partnership project (3GPP) for third-generation cellular telephony has defined a standard file format to contain audio/visual sequences which may be downloaded to cellular phones [3GPP]. At the time of writing, the 3GPP file format (3GP) can contain H.263 or MPEG-4 video, and AMR Narrow-band speech, AMR wide- band speech, or AAC audio, and 3GPP timed text.
Within the file, as with all files in the 'ISO' family, there is an intrinsic file-type box, which identifies those specifications to which the file complies, and which players (possibly compliant with only one specification) are permitted by the content author to play the file. This identification is through four-letter 'brands'.
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RFC 3839 MIME Type Registrations for 3GPP July 2004
Files identified by the MIME [MIME1] type defined here MUST contain a brand defined in a standard issued by 3GPP that can apply to 3GPP files, in their compatible brands list.
The MIME types defined here are needed to correctly identify such files when they are served over HTTP, included in multi-part documents, or used in other places where MIME types are used.
The 3GPP file format may contain audio, video, and displayable text data. There is currently no provision for 'active' elements (such as scripts) of any kind.
Clearly it is possible to author malicious files which attempt to call for an excessively large picture size, high sampling-rate audio etc. However, clients can and usually do protect themselves against this kind of attack.
It should be noted that selected metadata fields may encompass information partly intended to protect the media against unauthorized use or distribution. In this case, the intention is that alteration or removal of the data in the field would be treated as an offense under national agreements based on World Intellectual Property Organization (WIPO) treaties.
3GPP files have an extensible structure, so that it is theoretically possible that metadata fields or media formats could be defined in the future which could be used to induce particular actions on the part of the recipient, thus presenting additional security risks. However, this type of capability is currently not supported in the referenced specification.
There is no current provision in the standards for encryption, signing, or authentication of these file formats.
This registration applies to all files defined as using the '3GP' file format and identified with a suitable brand in a 3GPP specification. The usual file suffix for all these files is ".3gp".
The type "audio/3gpp" may be used for files containing audio but no visual presentation (neither video nor timed text, for example).
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RFC 3839 MIME Type Registrations for 3GPP July 2004
To: ietf-types@iana.org Subject: Registration of Standard MIME media type audio/3gpp
MIME media type name: audio MIME subtype name: 3gpp Required parameters: none Optional parameters: none Ongoing work related to this registration may introduce new optional parameters. One example area of effort may introduce a parameter that would allow for codecs in use within the MIME type to be asserted and determined without examination of the file. Those with interests in the area should monitor registrations for updates. Encoding considerations: files are binary and should be transmitted in a suitable encoding without CR/LF conversion, 7-bit stripping etc.; base64 is a suitable encoding. Note that this MIME type is used only for files; separate types are used for real-time transfer, such as for the RTP payload format for AMR audio [RFC3267]. Security considerations: see the security considerations section in RFC 3839 Interoperability considerations: The 3GPP organization has defined the specification, interoperability, and conformance, and conducts regular interoperability testing. Published specification: 3GPP 26.234, Release 5; 3GPP 26.244, Release 6 or later. 3GPP specifications are publicly accessible at the 3GPP web site, www.3gpp.org. Applications which use this media type: Multi-media Additional information: The type "audio/3gpp" MAY be used for files containing audio but no visual presentation. Files served under this type MUST NOT contain any visual material. (Note that 3GPP timed text is visually presented and is considered to be visual material).
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RFC 3839 MIME Type Registrations for 3GPP July 2004
Magic number(s): None. However, the file-type box must occur first in the file, and MUST contain a 3GPP brand in its compatible brands list. File extension(s): 3gp and 3gpp are both declared at http://www.nist.gov/nics/; 3gp is preferred Macintosh File Type Code(s): '3gpp' Person & email address to contact for further information: Nokia MIME manager, mime@nokia.com Intended usage: COMMON Change controller: 3GPP
The type "video/3gpp" is valid for all files. It is valid to serve an audio-only file as "video/3gpp".
To: ietf-types@iana.org Subject: Registration of Standard MIME media type video/3gpp
MIME media type name: video MIME subtype name: 3gpp Required parameters: none Optional parameters: none Encoding considerations: files are binary and should be transmitted in a suitable encoding without CR/LF conversion, 7-bit stripping etc.; base64 is a suitable encoding. Note that this MIME type is used only for files; separate types are used for real-time transfer, such as for the RTP payload formats for H.263 [RFC2429] and AMR audio [RFC3267]. Security considerations: see the security considerations section in RFC 3839 Interoperability considerations: The 3GPP organization has defined the specification, interoperability, and conformance, and conducts regular interoperability testing. Published specification: 3GPP 26.234, Release 5; 3GPP 26.244, Release 6 or later. 3GPP specifications are publicly accessible at the 3GPP web site, www.3gpp.org. Applications which use this media type: Multi-media
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RFC 3839 MIME Type Registrations for 3GPP July 2004
Additional information: Magic number(s): None. However, the file-type box must occur first in the file, and MUST contain a 3GPP brand in its compatible brands list. File extension(s): 3gp and 3gpp are both declared at http://www.nist.gov/nics/; 3gp is preferred Macintosh File Type Code(s): '3gpp' Person & email address to contact for further information: Nokia MIME manager, mime@nokia.com Intended usage: COMMON Change controller: 3GPP
The review of the 3GPP SA4 committee is gratefully acknowledged, in particular Per Frojdh. The chairs of the AVT working group, in particular Colin Perkins, have provided both excellent guidance and feedback, for which the authors are grateful.
[3GPP] Published specifications in releases 5 and 6: Release 5: 3GPP TS 26.234: Transparent end-to-end packet switched streaming service (PSS); Protocols and codecs. Release 6: 3GPP TS 26.244: Transparent end-to-end packet switched streaming service (PSS); 3GPP file format (3GP)
[MIME1] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
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RFC 3839 MIME Type Registrations for 3GPP July 2004
[RFC2429] Bormann, C., Cline, L., Deisher, G., Gardos, T., Maciocco, C., Newell, D., Ott, J., Sullivan, G., Wenger, S. and C. Zhu, "RTP Payload Format for the 1998 Version of ITU-T Rec. H.263 Video (H.263+)", RFC 2429, October 1998.
[RFC3267] Sjoberg, J., Westerlund, M., Lakaniemi, A. and Q. Xie, "Real-Time Transport Protocol (RTP) Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate WideBand (AMR-WB) Audio Codecs", RFC 3267, June 2002.
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