Re: [AVT] I-D ACTION:draft-ietf-avt-rtp-atrac-family-03.txt

[Matthew Romaine <Matthew.Romaine at jp.sony.com>]

Colin,

Thanks for your input.  The need for the auxiliary field is to have a  
mechanism to transmit metadata regarding the current stream, for  
example track name, artist, album title, etc.  While we might try to  
specify every entry, there will eventually be a field we miss.  I am  
thinking XML could be a solution as it allows tag defining.  Would it  
be alright if we specified the field to be of XML data?  We would  
like to retain the information under one session and hence payload  
since the streamed content may be relayed to devices unable to handle  
more than one session....

Regards,
Matt

> > On 2005/05/19, at 5:02, Colin Perkins wrote:
> > > On 18 May 2005, at 06:42, Matthew Romaine wrote:
> > > > An auxiliary data section has also been added.
> > >
> > > The auxiliary data section was introduced in the -02 revision. I  
> > > think the presence of this section is a mistake: it's better to  
> > > signal extensions in the signalling protocol, rather than  
> > > allowing undocumented auxiliary data. We don't typically allow  
> > > such undefined extension fields in RTP payload formats.
> >
> > There have been a few requests from internal groups in Sony for  
> > this part of the payload, as a) it minimizes resources otherwise  
> > used externally (i.e. if another separate payload would be used),  
> > and b) some groups have not solidified the parameters they might  
> > be using.  These groups are requesting a mechanism to send data  
> > with the payload rather than at, say, the SDP level.  Since there  
> > will be a level of generality somewhere in the pipeline, I modeled  
> > this section after the mpeg4 payload (RFC 3640) since that was an  
> > accepted method.
> >
> > Is that enough of a justification?
>
> No, I don't think so. This is one of the (many) problematic  
> features of the MPEG-4 payload format, which I do not recommend  
> copying.  There are several unused bits in your payload header  
> which can be used in a standard way from a revised payload format  
> in future, should they be needed.
>
> Colin



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