Re: [rtcweb] Proposed Plan for Usage of SDP and RTP - Lower level API minus SDP

Peter Thatcher <pthatcher@google.com> Thu, 07 March 2013 21:34 UTC

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From: Peter Thatcher <pthatcher@google.com>
Date: Thu, 7 Mar 2013 13:33:40 -0800
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To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
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Cc: "<rtcweb@ietf.org>" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Proposed Plan for Usage of SDP and RTP - Lower level API minus SDP
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A JSON format doesn't have to be "SDP in a different format".  It can
be much better.  It can expose an easy way to change the video
resolution to send, or a way to add/remove tracks easily.

Listing cameras, however, is a whole different topic.

On Thu, Mar 7, 2013 at 1:30 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> If your suggestion is only to convert the SDP to JSON, then that's a first
> step, but not the full story, because the complexity is just represented in
> a different format. I'm looking for something that helps programmers achieve
> their goals more easily.
>
> JSON is a first step, because it's a more readable data format. However, it
> doesn't help me, to e.g. list the cameras on offer and remove one, or change
> the offered video resolution. That needs manipulation functions.
>
>
>
> On Fri, Mar 8, 2013 at 8:25 AM, Peter Thatcher <pthatcher@google.com> wrote:
>>
>> So, would you like a SessionDescription that is easy to read and
>> manipulate, such as a JSON object?
>>
>> On Thu, Mar 7, 2013 at 1:22 PM, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>> > Agreed, but it's also not sufficient. SDP is not "programmer friendly"
>> > enough because it has too many details that are protocol-details only
>> > and
>> > it's too hard to see the semantic bits in SDP and ignore the rest.
>> >
>> > For example: the programmer wants to say - I want to get this video
>> > resolution, this audio bitrate & channels, I want to use this camera and
>> > this microphone for this call. Having to manipulate SDP directly for
>> > this is
>> > a programmer's nightmare.
>> >
>> > Silvia.
>> >
>> >
>> > On Fri, Mar 8, 2013 at 8:12 AM, Peter Thatcher <pthatcher@google.com>
>> > wrote:
>> >>
>> >> You can already do that by "munging" the SDP.  It's just not very
>> >> pleasant to do.
>> >>
>> >> On Thu, Mar 7, 2013 at 1:09 PM, Silvia Pfeiffer
>> >> <silviapfeiffer1@gmail.com> wrote:
>> >> > On Fri, Mar 8, 2013 at 5:51 AM, Mary Barnes
>> >> > <mary.ietf.barnes@gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> On Thu, Mar 7, 2013 at 12:42 PM, Eric Rescorla <ekr@rtfm.com> wrote:
>> >> >> >
>> >> >> > On Thu, Mar 7, 2013 at 9:56 AM, Mary Barnes
>> >> >> > <mary.ietf.barnes@gmail.com>
>> >> >> > wrote:
>> >> >> >>
>> >> >> >> On Thu, Mar 7, 2013 at 11:43 AM, Martin Thomson
>> >> >> >> <martin.thomson@gmail.com> wrote:
>> >> >> >> > Obviously I (and my employer) agree with these sentiments
>> >> >> >> > wholeheartedly.  Both Robin and Hadriel.
>> >> >> >> >
>> >> >> >> > That doesn't change the fact that a number of people are highly
>> >> >> >> > motivated to protect their investment in SDP offer/answer.  For
>> >> >> >> > those
>> >> >> >> > people, the pain that causes everyone else is clearly far less
>> >> >> >> > important than the pain they feel at this moment.  So here we
>> >> >> >> > are.
>> >> >> >>
>> >> >> >> [MB] I originally thought that either approach could work.  I did
>> >> >> >> see
>> >> >> >> the value that folks saw in using SDP offer/answer. But after
>> >> >> >> sitting
>> >> >> >> through the interim meeting last month, I am very much of the
>> >> >> >> mindset
>> >> >> >> that using SDP O/A is a bad idea.   I think many of us thought
>> >> >> >> that
>> >> >> >> using the SDP blob would help with interoperability with "legacy"
>> >> >> >> SIP
>> >> >> >> endpoints.  I don't see that now at all.  I think we will end up
>> >> >> >> with
>> >> >> >> a very fragile solution that will be very difficult to
>> >> >> >> extend/modify
>> >> >> >> later if we continue down the SDP O/A path.
>> >> >> >> [/MB]
>> >> >> >>
>> >> >> >
>> >> >> > Hasn't the WG already been asked this question not once but
>> >> >> > twice.
>> >> >> [MB] Yes.  And, some of us have changed our positions based upon the
>> >> >> challenges that the group is facing in getting the current approach
>> >> >> specified and agreed.  I don't disagree that it is not a good thing
>> >> >> that this is being discussed yet again.  [/MB]
>> >> >
>> >> >
>> >> > [Gotta love the triple negation!]
>> >> >
>> >> > Why can't we have it both ways?
>> >> >
>> >> > Maintain the current way to get the raw SDP using createOffer, but
>> >> > then
>> >> > provide an interface to change that offer before setLocalDescription.
>> >> >
>> >> > Even CISCO provides such an API:
>> >> >
>> >> >
>> >> > http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/sip_tn/8_5_1/4-sdp_api.html
>> >> > (I think we can do a better one than this, but it's a reference
>> >> > point).
>> >> >
>> >> > Cheers,
>> >> > Silvia.
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > rtcweb mailing list
>> >> > rtcweb@ietf.org
>> >> > https://www.ietf.org/mailman/listinfo/rtcweb
>> >> >
>> >
>> >
>
>