Intent to Implement and Ship: Partial RTCRtpReceiver and RTCRtpContributingSource

[Henrik Boström]

Contact emails

hb...@chromium.org, gui...@chromium.org, dead...@chromium.org

Spec

https://w3c.github.io/webrtc-pc/#rtcpeerconnection-interface-extensions

https://w3c.github.io/webrtc-pc/#dom-rtcrtpreceiver

https://w3c.github.io/webrtc-pc/#dom-rtcrtpcontributingsource

Summary While we intend to implement all of the RTP Media API (old intent to implement and ship), this intent is to first implement and ship a subset of the receiving parts of the API that is useful on its own.

This allows keeping track of which source is sending to a track when there are multiple sources that can send to a receiving track.

RTCPeerConnection extension:

- sequence<RTCRtpReceiver> getReceivers();

RTCRtpSender support:

- MediaStreamTrack track;

- sequence<RTCRtpContributingSource> getContributingSources();

RTCRtpContributingSource support:

- DOMHighResTimeStamp timestamp;

- unsigned long source;

- byte? audioLevel;

Motivation The W3C WebRTC working group has consensus around adding this API.

Compatibility Risk

Low risk. There is consensus and it is currently partially supported by other browsers:

https://developer.microsoft.com/en-us/microsoft-edge/platform/catalog/?q=specName%3Awebrtc%20rtpreceiver&page=1

https://developer.microsoft.com/en-us/microsoft-edge/platform/catalog/?q=specName%3Awebrtc%20contributing&page=1 Ongoing technical constraints

None Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes or no.

Yes. OWP launch tracking bug https://bugs.chromium.org/p/chromium/issues/detail?id=703122 Link to entry on the Chrome Platform Status https://www.chromestatus.com/feature/5715393821802496 Requesting approval to ship?

Yes.

[PhistucK]

Have you tried Firefox? MDN usually has an entry for everything it implements and those do not have entries. This worries me a bit.

☆PhistucK

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[the.s...@gmail.com]

We just haven't written those docs yet because priority-wise, we had other things that had to be done first. They're coming... :)

Eric Shepherd
Senior Technical Writer
Mozilla
https://developer.mozilla.org/
Blog: http://www.bitstampede.com/
Twitter: http://twitter.com/sheppy

☆PhistucK

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[Henrik Boström]

At the moment, Firefox stable has among the things listed in this intent RTCPeerConnection.getReceivers() and RTCRtpReceiver with track but no getContributingSources() yet.

[Philipp Hancke]

Firefox implements RTCRtpReceiver and getReceivers() but doesn't implement the getContributingSources method.

getContributingSources in Edge is from ORTC, the (webkit)RTCPeerConnection in Edge implements neither getSenders nor getReceivers currently (15.15055) so there is no way to get access those objects.

[Philip Jägenstedt]

I took a quick look at the API surface in the spec and filed one issue:

https://github.com/w3c/webrtc-pc/issues/1090

The biggest risk with shipping partial support might be if other browser supports more than that and that there's feature detection code that assumes support of that whole surface is present based on a single test. Happily, it looks like Gecko doesn't support RTCRtpContributingSource, and its RTCRtpReceiver has only the track attribute.

Edge 15 doesn't seem to have RTCRtpContributingSource, but its RTCRtpReceiver has a few things beyond track, namely onerror, rtcpTransport and transport. I don't know if that's cause for concern, but probably not since problematic code would already be broken in Firefox.

LGTM1

☆PhistucK

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[Dimitri Glazkov]

LGTM2

[Chris Harrelson]

LGTM3

LGTM2

☆PhistucK

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[Henrik Boström]

Update to technical constraints / RTCRtpContributingSource.audioLevel:

Because the audio level requires the support of a new RTP header extension we might not define audioLevel in the M59 shipping. (Current audio levels is currently available through other APIs which is sufficient for most use cases that are interested in audio level but not per-source and there isn't a history over the last 10 s.)

This shouldn't affect the arguments for or against this release though since the main thing with this feature is "source" and other browser don't deliver audioLevel either.

[Philip Jägenstedt]

Omitting audioLevel until it's clear how it should work SGTM.

LGTM3

LGTM2

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[Chris Harrelson]

Sounds fine to me too, thanks for asking. (No need to wait for a third piece of API owner feedback either.)

LGTM3

LGTM2

☆PhistucK

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