OggText - Revision history

Silvia: replaced "type" with "category" for codecs

2009-01-22T04:13:08Z

replaced "type" with "category" for codecs

Silvia: replacement of "type" with "category"

2009-01-22T04:05:35Z

replacement of "type" with "category"

← Older revision		Revision as of 04:05, 22 January 2009
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	= Categories of Text Codecs =		= Categories of Text Codecs =

	In a [https://wiki.mozilla.org/Accessibility/Video_a11y_requirements requirements study undertaken by Mozilla], a substantial number of text codec ~~types~~ has been identified.		In a [https://wiki.mozilla.org/Accessibility/Video_a11y_requirements requirements study undertaken by Mozilla], a substantial number of text codec categories has been identified.

	Prominent examples are:		Prominent examples are:

Silvia: added description of why duplicating information in headers and skeleton

2009-01-01T20:14:12Z

added description of why duplicating information in headers and skeleton

← Older revision		Revision as of 20:14, 1 January 2009
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	* Content-Language, e.g. en-AU, de-DE according to [http://www.ietf.org/rfc/rfc4646.txt rfc4646/bcp47] and http://www.iana.org/assignments/language-tags		* Content-Language, e.g. en-AU, de-DE according to [http://www.ietf.org/rfc/rfc4646.txt rfc4646/bcp47] and http://www.iana.org/assignments/language-tags
	* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)		* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)

			Note that duplication of this information inside the text codec header and here is intentional, since the text codec can then be used also with other encapsulation formats. The additional exposure of this information in the skeleton header allows this information to be available without any text codec libraries (e.g. in a Web proxy).

	== Data pages ==		== Data pages ==

Silvia: removed stray half sentence

2009-01-01T20:07:03Z

removed stray half sentence

← Older revision		Revision as of 20:07, 1 January 2009
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	Header packets must appear in order and all header packets must appear before any data packet. Each header packet is encapsulated in one Ogg page.		Header packets must appear in order and all header packets must appear before any data packet. Each header packet is encapsulated in one Ogg page.

	~~A codec that wants to use this specification~~

Silvia: better link

2008-11-26T11:14:15Z

better link

← Older revision		Revision as of 11:14, 26 November 2008
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	This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.		This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.

	Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. Non-text representations of subtitles (e.g. bitmaps), [http://en.~~wikipedia~~.~~org~~/~~wiki~~/~~Closed_captioning#Terminology~~ open captions] and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.		Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. Non-text representations of subtitles (e.g. bitmaps), [http://www.washington.edu/accessit/articles?1050 open captions] and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.

	A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.		A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.

Silvia: added a link to open captions

2008-11-26T11:12:32Z

added a link to open captions

← Older revision		Revision as of 11:12, 26 November 2008
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	This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.		This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.

	Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. Non-text representations of subtitles (e.g. bitmaps), open captions and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.		Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. Non-text representations of subtitles (e.g. bitmaps), [http://en.wikipedia.org/wiki/Closed_captioning#Terminology open captions] and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.

	A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.		A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.

Silvia: further clarified what goes into OggText

2008-11-26T11:02:43Z

further clarified what goes into OggText

← Older revision		Revision as of 11:02, 26 November 2008
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	This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.		This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.

	Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. ~~However, encapsulation of non~~-text representations of subtitles ~~& open captions~~ (e.g. bitmaps) and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.		Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. Non-text representations of subtitles (e.g. bitmaps), open captions and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.

	A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.		A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.

Silvia: clarified what is meant to go into OggText

2008-11-26T11:01:29Z

clarified what is meant to go into OggText

← Older revision		Revision as of 11:01, 26 November 2008
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	This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.		This page describes a generic media mapping (i.e. rules for multiplexing) of "text codecs" into Ogg.

	Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. However, encapsulation of non-text representations of e.g. ~~subtitles, closed captions~~ and ~~even~~		Text codecs are sequences of text chunks that have a timing relationship to an audio or video stream. A text codec relates to data that is logically regarded as text, in particular data of content-type <tt>text/*</tt>, but is not restricted to these. The format is in particular meant to be used for subtitles and closed captions. However, encapsulation of non-text representations of subtitles & open captions (e.g. bitmaps) and auditive audio descriptions (i.e. soundfiles) are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.
	audio descriptions are not meant to go into OggText, since they provide less flexibility for display mechanisms, search indexing, and general processing.

	A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.		A text codec should not contain binary data, in particular images. Where images are needed, they should be referenced. This can be done through a URL and thus having the image external to the media data. It could also be done by embedding the image inside the Ogg stream in a different track to the text codec. This is outside this specification though.

Silvia: added reference to rfc

2008-11-25T12:37:47Z

added reference to rfc

← Older revision		Revision as of 12:37, 25 November 2008
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	** if no [http://www.iana.org/assignments/character-sets charset parameter] is given, it defaults to UTF-8		** if no [http://www.iana.org/assignments/character-sets charset parameter] is given, it defaults to UTF-8
	** the default directionality of this text is implicitly given by the charset; text codecs are free to use additinal LTR/RTL information		** the default directionality of this text is implicitly given by the charset; text codecs are free to use additinal LTR/RTL information
	* Content-Language, e.g. en-AU, de-DE according to rfc4646 and http://www.iana.org/assignments/language-tags		* Content-Language, e.g. en-AU, de-DE according to [http://www.ietf.org/rfc/rfc4646.txt rfc4646/bcp47] and http://www.iana.org/assignments/language-tags
	* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)		* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)

Silvia: fixed the directionality question

2008-11-25T12:35:31Z

fixed the directionality question

← Older revision		Revision as of 12:35, 25 November 2008
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	* Content-Type, e.g. text/x-cmml, text/x-srt according to rfc2045		* Content-Type, e.g. text/x-cmml, text/x-srt according to rfc2045
	** if no [http://www.iana.org/assignments/character-sets charset parameter] is given, it defaults to UTF-8		** if no [http://www.iana.org/assignments/character-sets charset parameter] is given, it defaults to UTF-8
	** directionality of this text is implicitly given by the charset		** the default directionality of this text is implicitly given by the charset; text codecs are free to use additinal LTR/RTL information
	* Content-Language, e.g. en-AU, de-DE according to rfc4646 and http://www.iana.org/assignments/language-tags		* Content-Language, e.g. en-AU, de-DE according to rfc4646 and http://www.iana.org/assignments/language-tags
	* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)		* Text-Type, e.g. CC, SUB, etc (see abbreviations as defined above)

← Older revision		Revision as of 04:13, 22 January 2009
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	In Ogg, there is a sequence of header pages, a sequence of data pages, and an EOS page, which finishes the stream. The pages have to be ordered non-decreasing with time. No data can come before any of the header pages or after the EOS page.		In Ogg, there is a sequence of header pages, a sequence of data pages, and an EOS page, which finishes the stream. The pages have to be ordered non-decreasing with time. No data can come before any of the header pages or after the EOS page.

	Text codecs have to take complete care of their layout. E.g. if srt is encapsulated into Ogg with this mapping, it makes sense to specify the relative screen region into which the srt text segments are to be rendered in an srt header page. Otherwise the media player has to make assumptions based on the codec ~~type~~.		Text codecs have to take complete care of their layout. E.g. if srt is encapsulated into Ogg with this mapping, it makes sense to specify the relative screen region into which the srt text segments are to be rendered in an srt header page. Otherwise the media player has to make assumptions based on the codec category.

	[Possibly it makes sense to define some default layout options for the different codec ~~types~~.]		[Possibly it makes sense to define some default layout options for the different codec categories.]


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	\| Granuleshift \| Padding / future use \| 32-35		\| Granuleshift \| Padding / future use \| 32-35
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| Text ~~type~~ code \| 36-39		\| Text category code \| 36-39
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| Message header fields: Content-type & Content-language \| 40-		\| Message header fields: Content-type & Content-language \| 40-
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	3 Bytes padding data that may be used for future requirements and are mandated to zero in this revision.		3 Bytes padding data that may be used for future requirements and are mandated to zero in this revision.

	* Text ~~type~~ code:		* Text category code:
	A 4 Byte string signifying one of the text codec types as listed above. This provides information to the media player as to what kind of data to expect in the sequel.		A 4 Byte string signifying one of the text codec types as listed above. This provides information to the media player as to what kind of data to expect in the sequel.