Network Working Group Barry Short Internet-Draft The Ogg Vorbis Community / OpenDrama Expires: July 7, 2003 January 7, 2003 The audio/rtp-vorbis MIME Type draft-short-avt-rtp-vorbis-mime-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This internet draft will expire on July 7, 2003. 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 RFC 2119 [1]. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document explains the need for a MIME subtype which identifies a Vorbis audio payload to be used within a Realtime Transport Protocol (RTP) bitstream. This document also provides the necessary information to register audio/rtp-vorbis as a MIME type. Short Expires July 7, 2003 [Page 1] Internet-Draft draft-short-avt-rtp-vorbis-mime-00.txt January 2003 1. Introduction The Vorbis Bitstream format [5] developed by Xiph.org is a compressed audio format that uses pyschoacoustic compression algorithms with highly optimized bit-allocation. It has been developed as part of a larger project which aims to present a series of multimedia content carrier bitstreams, which are to be freely available to the computing community at large. These bitstreams are created by software or hardware encoder-decoders (codecs). For file based storage, Vorbis is generally encapsulated within the Ogg bitstream format described in [2]. However, raw packets from the Vorbis codecs can be used directly with transport mechanisms that provide their own framing and packet-separation. One such mechanism is the Real-time Transport Protocol (RTP), described in [3]. A payload format for using Vorbis audio over RTP is described in [4]. This document serves to register the audio/rtp-vorbis MIME type, and is a companion document to [4]. 2. Registration Information: To: ietf-types@iana.org Subject: Registration of MIME type audio/rtp-vorbis Media MIME type name: audio Media MIME subtype name: rtp-vorbis Required Parameters: none Optional Parameters: none Encoding Considerations: The Vorbis audio data is always wrapped within and RTP bitstream when transported with this MIME type. Since the Vorbis data is already compressed as detailed above, further lossless compression MAY be unnecessary. However, RTP header compression MAY be used to reduce the packet size. See [4] for further information on RTP encoding issues. Short Expires July 7, 2003 [Page 2] Internet-Draft draft-short-avt-rtp-vorbis-mime-00.txt January 2003 Security Considerations: The Vorbis format is highly specified [5] and so cannot contain security violating code. It could be possible to exploit errors or vulnerabilities in the decoder implementation, by abusing fields with arbitrary code. It is the decoder's responsibility to ensure that untrusted code is not executed. Vorbis bitstreams are neither signed nor encrypted, so external security systems should be added to ensure authenticity or confidentiality where required. Cryptographic authentication of incoming RTP and RTCP packets is highly recommended. Without such protections, attackers could corrupt the audio bitstream, potentially damaging speakers and eardrums. Further RTP security considerations are detailed in [3]. Interoperability Consideration: Conformance to the specification detailed in [4] ensures no interoperability issues need arise. Published Specification: See [4] Applications which use this media type: Any application which uses the specification outlined in [4] will be able to decode the bitestream. Additional Information: Magic Numbers: none File Extention: none Macintosh File Type Code: none Object Identifier(s) of OID(s): none Short Expires July 7, 2003 [Page 3] Internet-Draft draft-short-avt-rtp-vorbis-mime-00.txt January 2003 Person & Email address to contact for further information: For questions about this proposal contact: Barry Short . For technical questions about Vorbis see the mailing list of the developer community Internet Usage: COMMON Author/Change Controller: This document was written by Barry Short, changes of this document will be handled by the author or a representative of the Vorbis development community. 3. Security Considerations: Security considerations are discussed in the security considerations clause in section 2 of this document. 4. References 1. Key words for use in RFCs to Indicate Requirement Levels (RFC 2119) 2. The Ogg encapsulation format, Work in Progress, draft-pfeiffer-ogg-fileformat-00.txt 3. RTP: A Transport Protocol for Real-Time Applications, (RFC 1889) 4. RTP Payload Format for Vorbis Encoded Audio. Work in Progress, draft-kerr-avt-vorbis-rtp-00.txt 5. libvorbis: Available from Xiph website, http://www.xiph.org 5. Author's address Barry Short Centre for Music Technology University of Glasgow Glasgow UK G12 8LT Phone: +44 141 330 5740 Email: b.short@elec.gla.ac.uk Short Expires July 7, 2003 [Page 4] Internet-Draft draft-short-avt-rtp-vorbis-mime-00.txt January 2003 6. Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 7. Acknowledgement This document borrows from previous MIME type registrations, Internet-Drafts and RFCs. Thanks also to the Vorbis community. Short Expires July 7, 2003 [Page 5]