(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.