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

Colin Perkins csp at
Tue Sep 7 14:58:31 CEST 2004

On 7 Sep 2004, at 13:54, Jose Rey wrote:
>> 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.
> Ok, I was guiding myself more by the what I understood as type of apps.
> However, just for my clarity: if we wouldn't use the "relaxed rules" 
> could I still use text/? Is text/t140 conformat to the 'traditional 
> rules'?

None of the RTP payload formats -- not text, audio or video -- can be 
used with the 'traditional' rules. This is the reason why the MIME 
registration rules are being updated.

>>>>> 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.
> What I mean is what would be the use of having two, not one or the 
> other.

The media type for the file format may well be different than that for 
the RTP payload format, if that's what you mean.


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