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Re: active speaker information in mixed streams

From: Harald Alvestrand <harald@alvestrand.no>
Date: Fri, 07 Feb 2014 14:54:50 +0100
Message-ID: <52F4E5AA.8000904@alvestrand.no>
To: public-webrtc@w3.org
On 02/07/2014 11:09 AM, IƱaki Baz Castillo wrote:
> +1 for an API that retrieves the CSRC list of a receiving track (so
> the app could, somehow, map those SSRC values to a list of
> participants obtained by other means).
>
> In fact, it should be an event within the MediaStreamTrack that may
> fire every N seconds (when incoming RTP packets include a CSRC field):
>
> MediaStreamTrack.oncsrc =  function(sequence<ssrc>) {}

Absolutely disagree.

1) It is only needed when talking to devices that use CSRC mapping. This
is a property set that belongs to the peerconnection abstraction
(probably on the receiving doohickey), not to the more generic
MediaStram connection.

2) If this is going to be useful for active speaker switch indication,
the notification has to happen on a sub-second basis - too fast for a
reasonable periodic event.

(if you want to get a "feel" for the effect of delaying volume
indicators, play with the time constants in
https://code.google.com/p/webrtc/source/browse/trunk/samples/js/demos/html/local-audio-volume.html
- at the moment it is showing the result of sampling volume every 0.2
seconds.)

>
> 2014-02-07 Cullen Jennings (fluffy) <fluffy@cisco.com>:
>> On Jan 28, 2014, at 6:28 AM, Emil Ivov <emcho@jitsi.org> wrote:
>>
>>> Hey all,
>>>
>>> One requirement that we often bump against is the possibility to
>>> extract active speaker information from an incoming *mixed* audio
>>> stream. Acquiring the CSRC list from RTP would be a good solution to
>>> this. Audio levels as per RFC6465 would be even better.
>>>
>>> Are these something that could be foreseeable for 1.0 ?
>>>
>>> Emil
>> It seems like getting the CSRC from the stats API would be very helpful for a bunch of debugging audio issue as well
>>
>>
>>
>
>


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Received on Friday, 7 February 2014 13:55:19 UTC

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