Re: [rtcweb] Proposal for dealing with CNAMEs and MSIDs for synchronization

On 2013-02-10 23:36, Harald Alvestrand wrote:
> On 02/10/2013 01:47 PM, Stefan Håkansson LK wrote:
>> On 2013-02-09 15:40, Harald Alvestrand wrote:
>>> On 02/09/2013 02:11 PM, Stefan Håkansson LK wrote:
>>>> On 2013-02-08 22:37, Harald Alvestrand wrote:
>>
>> Just to verify that I get all of this correctly:
>> * There is a privacy issue if the app at the peer can find out if the
>> tracks for _different_ MediaStream's have local sources
>> * This could be found out if the CNAME's are the same and if CNAME's
>> are made available to the application
>> * Therefore we should have a design where tracks belonging to
>> different MediaStream's use different CNAME's even if they originate
>> from local sources at the same end-point
>>
>> Did I get that right?
> Points one and two, yes. Point three, no, that's not my thinking.
> I see no reason to force different CNAMEs, I just want to permit it.
>>
>> To me this seems far fetched. With this design you would have to
>> select between synchronization and privacy, if you care about privacy
>> each track would go to a different MediaStream (audio to one MS, video
>> to another in the simple "one audio+one video" case) and there would
>> be no sync.
>>
>> If this is indeed a problem, then there must be other ways. A setting
>> "privacy=on" on PeerConnection, or do not expose CNAME to the app (do
>> we really need to signal it?; and [1] indicates you can use other
>> CNAME's than those signaled).
> What I'd like to have is to have no statement that forces (even at
> SHOULD level) all local sources to have the same CNAME, and perhaps even
> an explicit statement that the sender can use different CNAMEs for local
> sources if it wants to (for whatever reason it wants to do so), as long
> as they are in different tracks.

The problem I have with this is that it makes it impossible for someone 
building a service to know whether streams will be synced (and I mean in 
situations when syncing makes sense - not when the video is delayed by 
500ms) or not. This is fully up to the browser - it may be that 
sometimes they are and sometimes not.

I would prefer that all streams used the same CNAME (if it is signaled 
or not is another question). If this is a privacy issue I think we 
should solve that instead of having the browser use, or not use, the 
same CNAMEs at its own will.

>
>
>
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