(per RFC4396) Media type: video Media subtype: 3gpp-tt Required parameters rate: Refer to Section 3 in RFC 4396. sver: The parameter "sver" contains a list of supported backwards-compatible versions of the timed text format specification (3GPP TS 26.245) that the sender accepts to receive (and that are the same that it would be willing to send). The first value is the value preferred to receive (or preferred to send). The first value MAY be followed by a comma-separated list of versions that SHOULD be used as alternatives. The order is meaningful, being first the most preferred and last the least preferred. Each entry has the format Zi(xi*256+yi), where "Zi" is the number of the Release and "xi" and "yi" are taken from the 3GPP specification version (i.e., vZi.xi.yi). For example, for 3GPP TS 26.245 v6.0.0, Zi(xi*256+yi)=6(0), the version value is "60". (Note that "60" is the concatenation of the values Zi=6 and (xi*256+yi)=0 and not their product.) If no "sver" value is available, for example, when streaming out of a 3GP file, the default value "60", corresponding to the 3GPP Release 6 version of 3GPP TS 26.245, SHALL be used. Optional parameters: tx: This parameter indicates the horizontal translation offset in pixels of the text track with respect to the origin of the video track. This value is the decimal representation of a 16-bit signed integer. Refer to TS 3GPP 26.245 for an illustration of this parameter. ty: This parameter indicates the vertical translation offset in pixels of the text track with respect to the origin of the video track. This value is the decimal representation of a 16-bit signed integer. Refer to TS 3GPP 26.245 for an illustration of this parameter. layer: This parameter indicates the proximity of the text track to the viewer. More negative values mean closer to the viewer. This parameter has no units. This value is the decimal representation of a 16-bit signed integer. tx3g: This parameter MUST be used for conveying sample descriptions out-of-band. It contains a comma-separated list of base64-encoded entries. The entries of this list MAY follow any particular order and the list SHALL NOT be empty. Each entry is the result of running base64 encoding over the concatenation of the (static) SIDX value as an 8-bit unsigned integer and the (static) sample description for that SIDX, in that order. The format of a sample description entry can be found in 3GPP TS 26.245 Release 6 and later releases. All servers and clients MUST understand this parameter and MUST be capable of using the sample description(s) contained in it. Please refer to RFC 3548 [6] for details on the base64 encoding. width: This parameter indicates the width in pixels of the text track or area of the text being sent. This value is the decimal representation of a 32-bit unsigned integer. Refer to TS 3GPP 26.245 for an illustration of this parameter. height: This parameter indicates the height in pixels of the text track being sent. This value is the decimal representation of a 32-bit unsigned integer. Refer to TS 3GPP 26.245 for an illustration of this parameter. max-w: This parameter indicates display capabilities. This is the maximum "width" value that the sender of this parameter supports. This value is the decimal representation of a 32-bit unsigned integer. max-h: This parameter indicates display capabilities. This is the maximum "height" value that the sender of this parameter supports. This value is the decimal representation of a 32-bit unsigned integer. Encoding considerations: This media type is framed (see Section 4.8 in [29]) and partially contains binary data. Restrictions on usage: This media type depends on RTP framing, and hence is only defined for transfer via RTP [3]. Transport within other framing protocols is not defined at this time. Security considerations: Please refer to Section 11 of RFC 4396. Interoperability considerations: The 3GPP Timed Text media format and its file storage is specified in Release 6 of 3GPP TS 26.245, "Transparent end-to- end packet switched streaming service (PSS); Timed Text Format (Release 6)". Note also that 3GPP may in future releases specify extensions or updates to the timed text media format in a backwards-compatible way, e.g., new modifier boxes or extensions to the sample descriptions. The payload format defined in RFC 4396 allows for such extensions. For future 3GPP Releases of the Timed Text Format, the parameter "sver" is used to identify the exact specification used. The defined storage format for 3GPP Timed Text format is the 3GPP File Format (3GP) [30]. 3GP files may be transferred using the media type video/3gpp as registered by RFC 3839 [31]. The 3GPP File Format is a container file that may contain, e.g., audio and video that may be synchronized with the 3GPP Timed Text. Published specification: RFC 4396 Applications which use this media type: Multimedia streaming applications. Additional information: The 3GPP Timed Text media format is specified in 3GPP TS 26.245, "Transparent end-to-end packet switched streaming service (PSS); Timed Text Format (Release 6)". This document and future extensions to the 3GPP Timed Text format are publicly available at http://www.3gpp.org. Magic number(s): None. File extension(s): None. Macintosh File Type Code(s): None. Person & email address to contact for further information: Jose Rey, jose.rey&eu.panasonic.com Yoshinori Matsui, matsui.yoshinori&jp.panasonic.com Audio/Video Transport Working Group. Intended usage: COMMON Authors: Jose Rey Yoshinori Matsui Change controller: IETF Audio/Video Transport Working Group delegated from the IESG.