Need guidance for implementing ice candidate pool

[Olivier Crête]

Hi,

Giving this a bit more though, I guess one could create those
unallocated streams hidden inside libnice and expose them when
nice_agent_add_stream() is called, but it's a bit trickier as that
means forcing eveyr stream to have the same number of components, which
isn't standard in ICE (but it's always true for webrtc as rtcp-mux is
mandated now).

Olivier

On Mon, 2021-05-03 at 15:42 -0400, Olivier Crête via gstreamer-devel
wrote:
> Hi,
> 
> With my libnice maintainer hat on, it's definitely something I would
> accept.
> 
> The tricky part is the implementation. At first, I though we'd want
> to create a new object separate from the ICE agent to do the
> gathering, but it gets quite tricky quickly as the gathering and
> especially TURN code is quite tied to the ICE agent code.
> 
> And looking at the spec, I think the implementation is mostly a
> webrtc level issue. All that you need to do is to add a new API to
> GstWebRTCICE to create GstWebRTCICEStream objects ahead of time and
> "cache" them, then when gst_webrtc_ice_add_stream() is called, you
> can just return one of the pre-allocated streams. The only issue is
> that we need to add an API to libnice to mark a stream "unallocated"
> so that it gets ignored when doing the freezing/unfreezing dance, and
> the same thing needs to happen inside webrtcbin so they get ignored
> when trying to compute the overall agent state.
> 
> Olivier
> 
> 
> On Mon, 2021-05-03 at 21:21 +0200, Mathieu Duponchelle via gstreamer-
> devel wrote:
> > Hey, this seems interesting, perhaps open an issue in libnice's
> > gitlab to discuss this?
> > 
> > On 5/2/21 5:29 AM, Sherrill Lam via gstreamer-devel wrote:
> > 
> > > 
> > > Hi there!
> > > 
> > > My team is interested to implement a prefetch ice candidate pool
> > > and add an ice-candidate-pool-size property ( [rtc
> > > spec](https://www.w3.org/TR/webrtc/#dom-rtcconfiguration-icecandidatepoolsize
> > > ) ) for webrtcbin element. We think it will help accelerate the
> > > SDP generation at startup process. We’d like to get more guidance
> > > on what would be the best way to do it.
> > > 
> > > Although ice candidate pool is a webrtc concept, I think it might
> > > make more sense if the pool itself is implemented within
> > > NiceAgent in Libnice. We could add an API in Libnice to create
> > > such a pool with a specified pool size and start generating ice
> > > candidates. When nice_agent_gather_candidates() is called, it
> > > will first check if there are candidates in the pool before
> > > generating new ones.
> > > 
> > > Any thoughts or suggestions?
> > > 
> > > Thanks!
> > > Sherrill
> > > 
> > > 
> > > _______________________________________________
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> 
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-- 
Olivier Crête
olivier.crete at collabora.com

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