Subject: [MMUSIC] Clearmode with multiple media types

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Wed, 9 Aug 2006 16:24:39 +0200

Hi,

If I use Clearmode to carry a 64kbit/s stream which contains multiple
media types (e.g. a multiplexed H.324 stream), what media type value in
the SDP m= line shall I use?

RFC4040 talks about "audio", but in this case the stream may contain
other media/data than audio.

The most logic option to me would be "data", but doesn't seem to be
in-line with the new SDP RFC... Or, would I have to writen an RFC to
describe this usage of "data"???

Regards,

Christer
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---

From: Gunnar Hellstrom <[email-masked]>
Date: Wed, 9 Aug 2006 16:31:54 +0100

Clearmode with multiple media typesWhat do you have in the channel?
V.80 modem tones from a PSTN connected H.324 or an H.324m datastream?

We have a similar problem with text telephony with origin in PSTN modem
tones.

There are some forces towards using RFC4351 carrying text-coded real-time
text with PSTN origin under MIME declaration audio/t140c so that it can be
interleaved with audio coders under the same m-line for the periods that the
session carries voice.

RFC 4351 was classified "Historical" already from publication in order to
remind implementors that this is not intended use of media descriptions and
discourage from widespread use in native IP environments.

We prefer to split the text telephony session in the text part, defined as
text/t140 as RFC 4103 and the audio part defined as audio/xxx with its
packetization, but there are situations when that is not easily done because
of gateway environment limitations.

I guess you will have similar problems if you were requested to split the
stream in m=video, m=audio and m=text .

I am interested to follow what advice you will get. It has general
applicability.

/ Gunnar
[email-masked]

  -----Original Message-----
  From: Christer Holmberg (JO/LMF) [mailto:[email-masked]]
  Sent: Wednesday, August 09, 2006 3:25 PM
  To: [email-masked]
  Subject: [MMUSIC] Clearmode with multiple media types

  Hi,

  If I use Clearmode to carry a 64kbit/s stream which contains multiple
media types (e.g. a multiplexed H.324 stream), what media type value in the
SDP m= line shall I use?

  RFC4040 talks about "audio", but in this case the stream may contain other
media/data than audio.

  Regards,

  Christer

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Wed, 9 Aug 2006 17:38:27 +0200

Hi, 

>What do you have in the channel? 

Well, the example I was thinking about is H.324m (sorry, I forgot the
"m" in the previous mail :). In that case the datastream could contain
audio, video, H.245, etc etc.
 
tones.
> 
>There are some forces towards using RFC4351 carrying text-coded
real-time text with PSTN origin under MIME declaration 
>audio/t140c so that it can be interleaved with audio coders under the
same m-line for the periods that the session 
>carries voice.
> 
>RFC 4351 was classified "Historical" already from publication in order
to remind implementors that this is not intended 
>use of media descriptions and discourage from widespread use in native
IP environments.
> 
>We prefer to split the text telephony session in the text part, defined
as text/t140 as RFC 4103 and the audio part 
>defined as audio/xxx with its packetization, but there are situations
when that is not easily done because of gateway 
>environment limitations.
> 
>I guess you will have similar problems if you were requested to split
the stream in m=video, m=audio and m=text .

If I de-multiplex the H.324m stream I will of course get individual
video streams (m=video), audio streams (m=audio) etc. But, until that I
only have a single stream, so I should be able to describe it with a
single m= line (m=<multiplexed H.324m datastream>).

Regards,

Christer

	-----Original Message-----
	From: Christer Holmberg (JO/LMF)
[mailto:[email-masked]]
	Sent: Wednesday, August 09, 2006 3:25 PM
	To: [email-masked]
	Subject: [MMUSIC] Clearmode with multiple media types

	Hi, 

	If I use Clearmode to carry a 64kbit/s stream which contains
multiple media types (e.g. a multiplexed H.324 stream), what media type
value in the SDP m= line shall I use?

	RFC4040 talks about "audio", but in this case the stream may
contain other media/data than audio. 

	The most logic option to me would be "data", but doesn't seem to
be in-line with the new SDP RFC... Or, would I have to writen an RFC to
describe this usage of "data"???

	Regards, 

	Christer

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Mon, 14 Aug 2006 17:57:09 +0200

Any comment on this? What media type value to use?

Regards,

Christer

-----Original Message-----

Sent: 9. elokuuta 2006 18:38
To: Gunnar Hellstrom; [email-masked]
Subject: RE: [MMUSIC] Clearmode with multiple media types

Hi, 

 
tones.
IP environments.

Regards,

Christer

	-----Original Message-----

	Hi, 

	Regards, 

	Christer

---

From: Gunnar Hellstrom <[email-masked]>
Date: Thu, 17 Aug 2006 22:52:09 +0200

RFC 2045 MIME Multipart says:

   In general, the top-level media type is used to declare the general
   type of data, while the subtype specifies a specific format for that
   type of data.  Thus, a media type of "image/xyz" is enough to tell a
   user agent that the data is an image, even if the user agent has no
   knowledge of the specific image format "xyz".  Such information can
   be used, for example, to decide whether or not to show a user the raw
   data from an unrecognized subtype -- such an action might be
   reasonable for unrecognized subtypes of text, but not for
   unrecognized subtypes of image or audio.  For this reason, registered
   subtypes of text, image, audio, and video should not contain embedded
   information that is really of a different type.  Such compound
   formats should be represented using the "multipart" or "application"
   types.

It seems as if "multipart" would be the correct media type for you, and a
specifically registered subtype for the multiplexing format.
However "multipart" is currently not included among the valid list of top
level media types for sdp, so it needs to get registered for that usage.

I am not sure this is the way mmusic want to go with componund media types.
?

Gunnar
----------------------------------------------------------------------------
-
Gunnar Hellstrom, Omnitor
[email-masked]
Mob: +46 708 204 288
Phone: +46 8 556 002 03
www.omnitor.se

-----Original Message-----
From: Christer Holmberg (JO/LMF) [mailto:[email-masked]]
Sent: Monday, August 14, 2006 5:57 PM
To: [email-masked]
Subject: RE: [MMUSIC] Clearmode with multiple media types

Regards,

Christer

-----Original Message-----

Hi,

tones.
IP environments.

Regards,

Christer

	-----Original Message-----

	Hi,

	Regards,

	Christer

---

From: Colin Perkins <[email-masked]>
Date: Fri, 18 Aug 2006 09:21:36 +0100

application/h324m although you'd need to register it first, of course.

Colin

---

From: "Belling, Thomas" <[email-masked]>
Date: Fri, 18 Aug 2006 14:15:19 +0200

Dear Christer,

using something like "application/h324M" to indicate that H.324M is
within the Clearmode codec is probably not the way to go, as this would
indicate that there is a particular RTP payload format for H.324M
directly within RTP.

Furthermore, given that the "clearmode" codec is defined in RFC 4040 and
MIME-registered under the "audio" type, there is little point in
changing that. "application" or something else might have been a better
choice, but the discussion is too late.

Another issue is that you desire to signal the contents of Clearmode. I
believe that "Clearmode" was originally designed for a SIP-I scenario,
where SIP is only in applied in a transit network and application
information is somewhere in the encapsulated ISUP.

If you still want to signal information about the applications within
clearmode on SDP level for other scenarios, one way to achieve that
would be to extend the clearmode MIME registration with optional
parameters to carry this information. However, I doubt that any native
SIP terminal would support the clearmode codec.

Thomas

> From: Colin Perkins [mailto:[email-masked]] 
> Sent: Friday, August 18, 2006 10:22 AM
> To: Christer Holmberg ((JO/LMF))
> Cc: [email-masked]
> Subject: Re: [MMUSIC] Clearmode with multiple media types
>

---

From: Colin Perkins <[email-masked]>
Date: Fri, 18 Aug 2006 13:37:31 +0100

Thomas,

You're right of course: if this is being sent within clearmode, the  
media type needs to indicate that clearmode is being used in the  
normal manner.

The alternative is to define an RTP payload format for h324M, instead  
of tunnelling inside clearmode. That would then use application/h324M  
as the media type.

Colin

---

From: "Belling, Thomas" <[email-masked]>
Date: Fri, 18 Aug 2006 15:08:02 +0200

"audio", because this is how clearmode is MIME-registered. 

> Sent: Friday, August 18, 2006 2:54 PM
> To: Belling, Thomas; Colin Perkins
> Cc: [email-masked]
> Hi Colin and Thomas,
> I think you missunderstood my question.
> 
> I am NOT proposing to change the "CLEARMODE" value, used in the rtpmap
> attribute.
> 
> I am asking what value to use for the media type part of the m= line?
> 
> m=<what value to use> 12345 RTP/AVP 97
> a=rtpmap:97 CLEARMODE/8000 
> 
> Regards,
> 
> Chriseter
> 
> 
> 
> 
> From: Belling, Thomas [mailto:[email-masked]] 
> Sent: 18. elokuuta 2006 15:15
> To: Colin Perkins; Christer Holmberg (JO/LMF)
> Cc: [email-masked]
> > >> We have a similar problem with text telephony with 
> origin in PSTN 
> > >> modem
> > > tones.
> > >>
> > > video streams (m=video), audio streams (m=audio) etc. But, until 
> > > that I only have a single stream, so I should be able to 
> describe it
> 
> > > with a single m= line (m=<multiplexed H.324m datastream>).
> > >
> > > Regards,
> > >
> > > Christer
> > >
> > >
> > >
> > >
> > > multiple media types (e.g. a multiplexed H.324 stream), 
> what media 
> > > type value in the SDP m= line shall I use?
> > >
> be

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Fri, 18 Aug 2006 15:13:10 +0200

Hi, 

>"audio", because this is how clearmode is MIME-registered. 

Yes. But, my question was whether "audio" really is the correct value,
if you have a multiplexed stream. I think that "data" would be much
better.

Regards,

Christer

> within the Clearmode codec is probably not the way to go, as this 
> would indicate that there is a particular RTP payload format for 
> H.324M directly within RTP.
> 
> Furthermore, given that the "clearmode" codec is defined in RFC 4040 
> and MIME-registered under the "audio" type, there is little point in 
> changing that. "application" or something else might have been a 
> better choice, but the discussion is too late.
> 
> Another issue is that you desire to signal the contents of Clearmode. 
> I believe that "Clearmode" was originally designed for a SIP-I 
> scenario, where SIP is only in applied in a transit network and 
> application information is somewhere in the encapsulated ISUP.
>

---

From: "Belling, Thomas" <[email-masked]>
Date: Fri, 18 Aug 2006 15:16:03 +0200

This is discussion that should have occured before the MIME
registration.
Now you need to comply with the "audio" registration.
Everything else would confuse existing implementations. 

> Sent: Friday, August 18, 2006 3:13 PM
> > > >> RFC 4351 was classified "Historical" already from 
> publication in 
> > > >> order
> > > >> use of media descriptions and discourage from 
> widespread use in 
> > > >> native
> > > > IP environments.
> > > >>
> > > >> We prefer to split the text telephony session in the 
> text part, 
> > > >> defined

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Fri, 18 Aug 2006 14:53:56 +0200

Hi Colin and Thomas,

Regards,

Chriseter

-----Original Message-----
From: Belling, Thomas [mailto:[email-masked]] 
Sent: 18. elokuuta 2006 15:15
To: Colin Perkins; Christer Holmberg (JO/LMF)
Cc: [email-masked]
Subject: RE: [MMUSIC] Clearmode with multiple media types

Dear Christer,

Thomas

> > that I only have a single stream, so I should be able to describe it

> > multiple media types (e.g. a multiplexed H.324 stream), what media 
be

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Thu, 24 Aug 2006 13:32:06 +0200

Hi,

RFC4040 says:

"Note: the choice of the "audio" top-level MIME type was
       made because the dominant uses of this pseudo-codec are
       expected to telephony and voice-gateway-related.  The
       "audio" type allows the use of sharing of the port in the
       SDP "m=" line with codecs such as audio/g711 [6], [7], for
       one example.  This sharing is an important application and
       would not be possible otherwise."

In the use-case I have in mind there would most likely be no "sharing of
the port", i.e. the m= line would only contain the clearmode codec, and
no audio codecs.

Regards,

Christer