Re: [AVT] Re: draft-jones-avt-audio-t38-04.txt

[Magnus Westerlund <magnus.westerlund at ericsson.com>]

Hi,

As I understand it, the below SDP attributes are in fact only used when 
the usage is with m= lines that looks like the following (using udptl or 
tcp as protocol):

From section D.2.4.1 of T.38

m=image 49170 udptl t38
a=T38FaxRateManagement:transferredTCF
a=T38FaxUdpEC:t38UDPFEC
m=image 49172 tcp t38
a=T38FaxRateManagement:localTCF

While what we are now defining is the parameter that belongs to the T.38 
RTP payload format. This new payload format should really use the 
standard procedures for any m= line with RTP in it. Therefore you need 
to follow the methods in RFC 3555 for this.

Cheers

Magnus

Colin Perkins wrote:

> On Tuesday 25 May 2004 18:12, Mundra, Satish wrote:
>
> > Magnus,
> >
> >
> > Currently following attributes have been registered with IANA for
> > att-field (media-level) for use with image/t38.
> >          
> >                T38FaxVersion                [ITU-T Rec. T.38 Annex D]
> >                T38maxBitRate                [ITU-T Rec. T.38 Annex D]
> >                T38FaxFillBitRemoval         [ITU-T Rec. T.38 Annex D]
> >                T38FaxTranscodingMMR         [ITU-T Rec. T.38 Annex D]
> >                T38FaxTranscodingJBIG        [ITU-T Rec. T.38 Annex D]
> >                T38FaxRateManagement         [ITU-T Rec. T.38 Annex D]
> >                T38FaxMaxBuffer              [ITU-T Rec. T.38 Annex D]
> >                T38FaxMaxDatagram            [ITU-T Rec. T.38 Annex D]
> >                T38FaxUdpEC                  [ITU-T Rec. T.38 Annex D]
> >
> >
> > Why not simply reuse them for audio/t38 too instead of registering new
> > ones ? It will simplify handling of SDP for those that currently
>
> support
>
> > image/t38.
>
>
> Well...  these should have been registered as MIME parameters for use in
>
> "a=fmtp:", rather than as attributes. As it stands, they're inconsistent
>
> with other payload formats.
>
> Colin

--

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: magnus.westerlund at ericsson.com


_______________________________________________
Audio/Video Transport Working Group
avt at ietf.org
https://www1.ietf.org/mailman/listinfo/avt