Re: [MMUSIC] Proposal for what bundle should say about demux

On 5/24/13 5:14 AM, Emil Ivov wrote:
> On 24.05.13, 12:02, Kevin Dempsey wrote:
>> I didn't say anything about changing the PTs.
>
> Sorry, I misunderstood.
>
>> The answerer decides what
>> it codecs it will use from the ones listed in the offer. If it doesn't
>> support any other mechanism to allow demux then it must choose codecs
>> that have PTs on only one m-line, or not accept the BUNDLE.
>
> Matching packets to m= lines is the concern of the receiving party. So
> is the mechanism that it uses. What you are suggesting is for the
> answerer to basically say: "It seems to me that you won't be able to
> demux these two payloads so I will not send them to you because I know
> better".
>
> In the same time the offerer may be planning on using a demux technique
> that the answerer simply isn't aware of. For example (and this is really
> just to make a point, so please don't assume I am suggesting something
> like this in general) if 101 is mapped to both telephone-event and VP8,
> demuxing can be easily made without any other knowledge of SSRC or
> header extensions.

ISTM that after the O/A exchange both sides need to have a common 
understanding that their communications will be understandable.

If the combination of the offer and answer aren't sufficient for each 
side to encode what it sends in a way that it knows can be demuxed 
according in accord with the O/A, then that offer should be incorrect.

IMO injecting "magic" into this isn't helpful.

	Thanks,
	Paul

> Cheers,
> Emil
>
>
>>
>>
>> On 24 May 2013 09:59, Emil Ivov <emcho@jitsi.org
>> <mailto:emcho@jitsi.org>> wrote:
>>
>>      On 24.05.13, 11:40, Kevin Dempsey wrote:
>>      > Isn't the onus on the answerer to ensure the demux is possible,
>>      since it
>>      > is accepting the bundle. Therefore if it doesn't support signalling
>>      > SSRCs or an offerred 'fancy-RFC m-line matching' method, it must only
>>      > send PTs that are tied to a single m-line.
>>
>>      PTs are defined by the offerer. The answerer cannot change them for the
>>      offerer-bound direction (even if it could request different values for
>>      the packets that it, the answerer, is going to receive).
>>
>>      Emil
>>
>>
>>      >
>>      >
>>      > On 24 May 2013 08:17, Emil Ivov <emcho@jitsi.org
>>      <mailto:emcho@jitsi.org>
>>      > <mailto:emcho@jitsi.org <mailto:emcho@jitsi.org>>> wrote:
>>      >
>>      >     On 24.05.13, 00:59, Paul Kyzivat wrote:
>>      >     > IMO the "before the O/A completes" issues are separate from
>>      the "after
>>      >     > the O/A completes" issues. I'm still not convinced that the
>>      >     "before the
>>      >     > O/A completes" issues are important. (We have reliable 183
>>      >     responses to
>>      >     > deal with it.) But I'm ok with Cullen using PT to solve that
>>      >     problem if
>>      >     > he thinks he needs to.
>>      >
>>      >     I wasn't referring to "before the O/A completes" situations.
>>      If your
>>      >     peer does not support fancy-RFC m-line matching nor does it
>>      provide
>>      >     SSRCs, you have to be able to fall back to PT demuxing.
>>      >
>>      >     Therefore, all your offers have to accommodate for that
>>      possibility
>>      >     unless you know that the offer is going to someone who also
>>      supports
>>      >     other mechanisms.
>>      >
>>      >     Emil
>>      >
>>      >     --
>>      >     https://jitsi.org
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>>      >
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>