Aiortc-datachannel-only

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* Defer adding remote candidates until after transport bundling to avoid
unnecessary mDNS lookups.

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* Add support for resolving mDNS candidates.
* Improve support for TURN, especially long-lived connections.

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Breaking
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* Make :meth:`RTCPeerConnection.addIceCandidate` a coroutine.
* Make :meth:`RTCIceTransport.addRemoteCandidate` a coroutine.

Media
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* Handle SSRC attributes in SDP containing a colon (372).
* Limit number of H.264 NALU per packet (394, 426).

Examples
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* `server` make it possible to specify bind address (347).

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Provide binary wheels for Linux, Mac and Windows on PyPI.

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Data channels
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* Add :attr:`RTCSctpTransport.maxChannels` property.
* Recycle stream IDs (256).
* Correctly close data channel when SCTP is not established (300).

Media
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* Add add :attr:`RTCRtpReceiver.track` property (298).
* Fix a crash in `AimdRateControl` (295).

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DTLS
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* Drop support for OpenSSL < 1.0.2.

Examples
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* `apprtc` fix handling of empty "candidate" message.

Media
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* Fix a MediaPlayer crash when stopping one track of a multi-track file (237, 274).
* Fix a MediaPlayer error when stopping a track while waiting for the next frame.
* Make `RTCRtpSender` resilient to exceptions raised by media stream tracks (283).