Bug 158191 – WebRTC: Update RTCPeerConnection.addTrack() to create (or reuse) an RTCRtpTransceiver

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore Misc.

[Adam Bergkvist]

When addTrack is called, there might be an existing RTCRtpTransceiver with an RTCRtpSender that can be reused. This procedure is described at [1].

[1] https://w3c.github.io/webrtc-pc/archives/20160513/webrtc.html#dom-rtcpeerconnection-addtrack

[Adam Bergkvist]

Created attachment 280254 [details]
Proposed patch

[Eric Carlson]

Comment on attachment 280254 [details]
Proposed patch

View in context: https://bugs.webkit.org/attachment.cgi?id=280254&action=review

> Source/WebCore/Modules/mediastream/RTCPeerConnection.h:67
> +    Vector<RefPtr<RTCRtpSender>> getSenders() const override { return m_transceiverSet->getSenders(); }
> +    Vector<RefPtr<RTCRtpReceiver>> getReceivers() const { return m_transceiverSet->getReceivers(); }

Can these return a reference to a const Vector: "const Vector<RefPtr<...>>&"?

> Source/WebCore/Modules/mediastream/RTCPeerConnection.h:68
> +    const Vector<RefPtr<RTCRtpTransceiver>>& getTransceivers() const override { return m_transceiverSet->list(); }

Can this be final instead of override?

[Adam Bergkvist]

(In reply to comment #2)
> Comment on attachment 280254 [details]
> Proposed patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=280254&action=review
> 
> > Source/WebCore/Modules/mediastream/RTCPeerConnection.h:67
> > +    Vector<RefPtr<RTCRtpSender>> getSenders() const override { return m_transceiverSet->getSenders(); }
> > +    Vector<RefPtr<RTCRtpReceiver>> getReceivers() const { return m_transceiverSet->getReceivers(); }
> 
> Can these return a reference to a const Vector: "const Vector<RefPtr<...>>&"?

Yes they can; and probably should :). createOfferTask uses getSenders() and modifies the resulting vector, but it can create a new vector from the const ref for its special purpose.

> > Source/WebCore/Modules/mediastream/RTCPeerConnection.h:68
> > +    const Vector<RefPtr<RTCRtpTransceiver>>& getTransceivers() const override { return m_transceiverSet->list(); }
> 
> Can this be final instead of override?

Seems to work. I'm a bit unsure what the result is being that the entire class is final.

[Adam Bergkvist]

Created attachment 280309 [details]
Updated patch

Made getSenders/Receivers() return a const Vector ref.

Kept 'override' on getTransceivers() since, to my understanding, final doesn't provide any extra functionality when the class is final already. I may be wrong on this though.

[Adam Bergkvist]

Comment on attachment 280309 [details]
Updated patch

Thanks for reviewing Eric!

[WebKit Commit Bot]

Comment on attachment 280309 [details]
Updated patch

Clearing flags on attachment: 280309

Committed r201601: <http://trac.webkit.org/changeset/201601>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Darin Adler]

Comment on attachment 280309 [details]
Updated patch

View in context: https://bugs.webkit.org/attachment.cgi?id=280309&action=review

> Source/WebCore/Modules/mediastream/MediaEndpointPeerConnection.cpp:135
> +    RtpSenderVector senders = RtpSenderVector(m_client->getSenders());

I don’t think we need to state the class name twice. Default behavior when receiving a const& is to make a copy, in fact, this should work:

    auto senders = m_client->getSenders();

But we need a comment explaining why we need a copy rather than using the reference. The copy is expensive.

[Adam Bergkvist]

Comment on attachment 280309 [details]
Updated patch

View in context: https://bugs.webkit.org/attachment.cgi?id=280309&action=review

>> Source/WebCore/Modules/mediastream/MediaEndpointPeerConnection.cpp:135
>> +    RtpSenderVector senders = RtpSenderVector(m_client->getSenders());
> 
> I don’t think we need to state the class name twice. Default behavior when receiving a const& is to make a copy, in fact, this should work:
> 
>     auto senders = m_client->getSenders();
> 
> But we need a comment explaining why we need a copy rather than using the reference. The copy is expensive.

The content of this function is replaced in https://bugs.webkit.org/show_bug.cgi?id=158203.