Informational F. Wong Internet Draft M. Macauley Intended status: Informational Harmonic Inc. Expires: December 26, 2012 June 2012 SMPTE-TT Embedded in ID3 for HTTP Live Streaming draft-smpte-id3-http-live-streaming-00 Abstract This document describes how the subtitle feature for different languages can be achievable in HTTP Live Streaming output streams. In order to achieve the goal, SMPTE-TT XML files are used to embed into the ID3 tag with user defined languages and text information stored in multiple frames. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, and it may not be published except as an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on December 26, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Wong & Macauley Expires December 26, 2012 [Page 1] Internet-Draft June 2012 Table of Contents 1. Introduction....................................................3 2. Conventions Used in This Document...............................3 3. ID3 Tag.........................................................3 3.1. User Defined Text Information Frame........................3 4. Presentation Time of Temporal Structuring Element in SMPTE-TT...4 5. Examples........................................................4 5.1. SMPTE-TT Example...........................................4 6. Security Considerations.........................................5 7. IANA Considerations.............................................5 8. References......................................................5 8.1. Normative References.......................................5 8.2. Informative References.....................................5 Authors' Addresses..................................................6 Wong & Macauley Expires December 26, 2012 [Page 2] Internet-Draft June 2012 1. Introduction Apple HTTP Live Streaming supports inclusion of timed metadata in ID3 format, carried in an elementary stream (PES) of MPEG-2 transport stream. The metadata stream will be in the same program as the main program containing video/audio content. Based on this mechanism, the SMPTE-TT XML files containing subtitle images are tagged by the ID3 tag and are embedded as timed metadata in TS segments according to the Apple HLS Metadata Specification. 2. Conventions Used in This Document 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 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. 3. ID3 Tag The ID3 Tag [ID3] contains the description of the subtitle and the content of SMPTE-TT XML files. The user defined text information frame (TXXX) defined in (ID3 tag version 2.3.0) is used when tagging the content. 3.1. User Defined Text Information Frame The SMPTE-TT XML files containing subtitle images are stored in a complete "User Defined Text Information Frame" (TXXX). The following attributes are defined: FRAME HEADER The value is ID3 Frame header. TEXT ENCODING The value is the text encoding byte. It denotes the text encoding used to encode the DESCRIPTION and VALUE field. DESCRIPTION The description contains Track Name and Language Descriptor in a text string encoded according to TEXT ENCODING. Track Name refers to a unique identifier of closed caption. Language Descriptor is used according ISO639-1. Wong & Macauley Expires December 26, 2012 [Page 3] Internet-Draft June 2012 E.g. If Track Name = 1, Language Descriptor = eng, the description would be Track:1,Lang:eng. VALUE The value is SMPTE-TT XML encoded according to TEXT ENCODING. 4. Presentation Time of Temporal Structuring Element in SMPTE-TT Temporal structures in SMPTE-TT contain the time information in XML attributes using timeExpression [W3C-TTML-1.0]. The timeExpression MUST be interpreted as relative to the presentation time of containing the ID3 Tag. 5. Examples 5.1. SMPTE-TT Example
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Wong & Macauley Expires December 26, 2012 [Page 4] Internet-Draft June 2012 6. Security Considerations Since the protocol relies on HTTP Live Streaming, most of the same security considerations apply. See section 11 of draft-pantos-http- live-streaming-08. 7. IANA Considerations Same IANA considerations of HTTP Live Streaming apply. See section 10 of draft-pantos-http-live-streaming-08. 8. References 8.1. Normative References [SMPTE377M] Society of Motion Picture and Television Engineers, "Material Exchange Format (MXF) File Format Specification", SMPTE 377M-2004, . [SMPTE400M] Society of Motion Picture and Television Engineers, "SMPTE Labels Structure", SMPTE 400M-2004, . 8.2. Informative References [ID3] ID3.org, "User defined text information frame", < http://www.id3.org/id3v2.3.0#head- 29e37534e169ad913deb6a4fee345028f3db7c3f>. [W3C-TTML-1.0] W3C, "Time Value Expression",< http://www.w3.org/TR/ttaf1-dfxp/#timing-value- timeExpression>. Wong & Macauley Expires December 26, 2012 [Page 5] Internet-Draft June 2012 Authors' Addresses Fei Wong Harmonic Inc. 4300 North First Street San Jose, CA 95134 United States Email: fei.wong@harmonicinc.com Moore Macauley Harmonic Inc. 4300 North First Street San Jose, CA 95134 United States Email: moore.macauley@harmonicinc.com Wong & Macauley Expires December 26, 2012 [Page 6]