Internet DRAFT - draft-smpte-id3-http-live-streaming
draft-smpte-id3-http-live-streaming
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
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This Internet-Draft will expire on December 26, 2012.
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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
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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.
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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
<tt xml:lang="CHI" xmlns="http://www.w3.org/ns/ttml"
xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
xmlns:tts="http://www.w3.org/ns/ttml#style"
xmlns:smpte="http://www.smpte-ra.org/schemas/2052-1/2010/smpte-tt">
<head />
<body>
<div begin="00:00:01:229" end="00:00:02:152" tts:extent="39% 6%"
tts:origin="30% 87%">
<metadata>
<smpte:image imagetype="PNG" encoding="Base64">
iVBO
...
gg==
</smpte:image>
</metadata>
</div>
<div begin="00:00:02:199" end="00:00:03:0" tts:extent="20% 6%"
tts:origin="39% 87%">
<metadata>
<smpte:image imagetype="PNG" encoding="Base64">
iVBO
...
</smpte:image>
</metadata>
</div>
</body>
</tt>
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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,
<http://www.smpte.org>.
[SMPTE400M] Society of Motion Picture and Television
Engineers, "SMPTE Labels Structure", SMPTE 400M-2004,
<http://www.smpte.org>.
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>.
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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
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