Registration of media type text/3gpp-tt
Jose Rey
rey at panasonic.de
Mon Sep 13 10:29:51 CEST 2004
Hello,
please consider the following media type text/3gpp-tt for registration under
the IETF tree. This section is copied from the draft
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-3gpp-timed-text-06.tx
t.
MIME type: text
MIME subtype: 3gpp-tt
Required parameters
rate:
the RTP timestamp clockrate is equal to the clockrate of
the media. If RTP packets are generated out of a 3GP
file, the clockrate of the text media MUST be copied
from the 3GP file, i.e. the clockrate is the value of
"timescale" parameter in the Media Header Box describing
that text track. Other tracks (audio/video/text) in the
3GP file may have their own clockrates as indicated in
their corresponding Media Header Box. For live
encoding, a clockrate of 1000 Hz is RECOMMENDED but
other values MAY be used. If a different timestamp rate
value is used, this MUST be chosen carefully as per
Section 3 in RFCXXXX.
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 which are the same that it would be
willing to send). The first value is the value
preferred to be received ( 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,
"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 its product.)
width:
This parameter indicates the width in pixels of the text
track or area of the text being sent. This is a 16 bit
integer.
height:
This parameter indicates the height in pixels of the
text track being sent. This is a 16 bit integer.
max-w:
This parameter indicates display capabilities. This is
the maximum "width" value that the sender of this
parameter supports. This is a 16 bit unsigned integer.
max-h:
This parameter indicates display capabilities. This is
the maximum "height" value that the sender of this
parameter supports. This is a 16 bit unsigned integer.
tx:
This parameter indicates the horizontal translation
offset in pixels of the text track with respect to the
origin of the video track. This is a 16 bit integer.
ty:
This parameter indicates the vertical translation offset
in pixels of the text track with respect to the origin
of the video track. This is a 16 bit integer.
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 is a 16 bit
integer.
Optional parameters:
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 that MAY follow any particular order and the list
MAY be empty. The absence of this parameter is
equivalent to an empty list of sample descriptions.
Each entry is the result of running base64 encoding over
the concatenation of the SIDX and the sample description
for that SIDX, in this 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.
Encoding considerations:
RTP payloads complying with this payload format contain binary
data.
Note that this type is incompatible with the use of text media
types in other protocols, e.g. text/html. This is because in
order to extract and decode any of the timed text media it is
necessary understand the (binary) payload headers defined in
RFCXXXX.
Restrictions on usage:
This type is only defined for transfer via RTP.
Security considerations:
Please refer to Section 10 of RFCXXXX.
Interoperability considerations:
The 3GPP Timed Text media format for which this payload format
is defined is specified in Release 6 of 3GPP TS 26.245
"Transparent end-to-end packet switched streaming service (PSS);
Timed Text Format (Release 6)". The 3GPP file format (3GP) and
the SMIL language profile used can be found in Release 5 of 3GPP
TS 26.234 and in the corresponding specifications for later
Releases. Note also that 3GPP may in future Releases specify
extensions or updates to the media format in a backwards-
compatible way, e.g. new modifier boxes or extensions to the
sample descriptions. The payload format defined in RFCXXXX
Rey & Matsui [Page 29]
Internet Draft Payload Format for 3GPP Timed Text September 10, 2004
allows for such extensions. For future 3GPP Releases of the
Timed Text Format, the parameter "sver" is used to identify the
exact specification used.
Published specification: RFC XXXX
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, rey at panasonic.de
Yoshinori Matsui, matsui.yoshinori at jp.panasonic.com
Audio/Video Transport Working Group.
Intended usage: COMMON
Author/Change controller:
Jose Rey
Yoshinori Matsui
IETF AVT WG
Thank,
---------------------------------
Jose Rey
Mobile Multimedia Team
Panasonic R&D Center Germany GmbH
D-63225 Langen, Germany
Tel.:+49-6103-766-134
Fax :+49-6103-766-166
Email: rey at panasonic.de
Web: www.prdcg.panasonic.de
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