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

Jose Rey rey at
Tue Sep 7 13:56:26 CEST 2004


Thanks for your answers. See inline.

> -----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)
> Jose,
> 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?


> 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

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



> Colin

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