Media Types in 3GPP Timed text draft (was: RE: [AVT] RTP andMediaTypes)

Colin Perkins csp at
Tue Sep 7 14:25:52 CEST 2004


On 7 Sep 2004, at 12:56, Jose Rey wrote:
>> -----Original Message-----
>> From: Colin Perkins [mailto:csp at]
>> Sent: Tuesday, September 07, 2004 12:03 PM
>> To: Jose Rey
>> Cc: IETF AVT WG; Dave Singer; Magnus Westerlund; IETF-Types
>> Subject: Re: Media Types in 3GPP Timed text draft (was: RE: [AVT] RTP 
>> andMediaTypes)
>> On 17 Aug 2004, at 14:42, Jose Rey wrote:
>>> Dave and I have been discussing this offline and come to the 
>>> following
>>> conclusions:
>>> 1.- it is not envisioned that the 3GPP Timed Text payload format will
>>> be
>>> used for applications such as instant messaging or text conversation,
>>> which do not precise of text decoration for working properly, since
>>> there are other more appropriate media types covering these usages,
>>> like text/t140. Hence,  video/ is enough.
>> I agree that this is not likely to be used for instant messaging or
>> text conversation, although I don't understand why that would be
>> relevant?
> below..
>> Is this fundamentally text or a video codec? If it's a video
>> codec, it should be under "video/", otherwise under "text/".
> I think it is a video codec, since without the video capabilities
> (modifiers) it would just provide the same services as , e.g.,
> conversational text=just plain timed text, for which it is not thought 
> to be used.

There are other text formats that include formatting modifiers, for 
example "text/html". I don't understand why their presence would make 
this a video format.

>>> 2.- we are not clear on what exactly means to "relax rules for media
>>> registration under text/".  I.e. is text/t140 an example of these
>>> "relaxed" rules or does it comply with the traditional rules as per
>>> rfc 2046?  Does the relaxed rules just mean that besides text also
>>> payload headers of that media type are udnerstood?
>> My understanding is that the new rules are intended to allow formats
>> such as 3GPP timed text to be registered under the text top-level 
>> media
>> type, if appropriate, provided their domain of applicability is 
>> clearly
>> specified (e.g. the domain of applicability might be that the type is
>> defined for transfer via RTP only).
> The MIME subtype /3gpp-tt cannot be used for HTML download since for 
> that
> purpose a 3gp file and therefore the video/3gp MIME type is used.  So I
> think this is indeed restricted to RTP.  However,  what is the gain of 
> doing that?

My point was that, since this is restricted to transport via RTP, it 
can be registered under the "text" top-level media type.

> Given the answer to the first question I think registering under
> text/ would not be of any use?

Why not? It would seem to be the natural home for a timed text format.


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