Safari <=12.0 media establishing does not work due to `removeExtmapAllowMixed` shim not being applied

[ostap0207]

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• I have provided steps to reproduce (e.g. a link to a jsfiddle)
• I have provided browser name, version and adapter.js version
• This issue only happens when adapter.js is used

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Versions affected

Safari 12.0

adapter.js 7.7.0, 7.7.1, 8.0

Description

removeExtmapAllowMixed shim is not applied to iOS Safari 12.
Based on this PR's comments the shim should be applied to Safari < 13.1, however it is not applied in iOS Safari 12.

I think the culprit is this check https://github.com/webrtcHacks/adapter/blob/master/src/js/common_shim.js#L327

  if (browserDetails.browser === 'safari' && browserDetails.version >= 605) {
    return;
  }

browserDetails.version returns AppleWebKit version and this version is 605 in both iOS Safari 12 and iOS Safari 13.
For example here is UserAgent from iOS Safari 12:
Mozilla/5.0 (iPhone; CPU iPhone OS 12_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.0 Mobile/15E148 Safari/604.1
here is UserAgent from iOS Safari 13:
Mozilla/5.0 (iPhone; CPU iPhone OS 13_2_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Mobile/15E148 Safari/604.1

Based on local testing this shim is only needed in Safari 12.0 and below, as all works correctly in Safari 12.1+

Steps to reproduce

1. Go to https://appr.tc/ in Chrome 91 and create a room
2. Go to that room from iOS Safari 12, allow camera, in console paste the latest adapter release https://github.com/webrtcHacks/adapter/blob/master/release/adapter.js. This is because https://appr.tc/ does not use the newest version at the moment.
3. In iOS Safari press Join

Expected results

2-way video is established

Actual results

Error: setRemoteDescription: OperationError: Expects at least 2 fields.

[hthetiot]

How about using feature detection instead of user agent sniffing. All what is needed is try setRemoteDescription with extmap in a test RTCconnection, that much more reliable than user agent sniffing.

[ostap0207]

Wouldn't this require to always override setRemoteDescription, while we probably should override it only when needed?

[ostap0207]

Any updates on this? This breaks media establishing with Safari 12.0 for us.

[hthetiot]

you can always do that in the meantime on your signaling layer.

        // Remove extmap-allow-mixed sdp header
	if (desc && desc.sdp && desc.sdp.indexOf('\na=extmap-allow-mixed') !== -1) {
		desc = new RTCSessionDescription({
			type: desc.type,
			sdp: desc.sdp
				.split('\n')
				.filter((line) => {
					return line.trim() !== 'a=extmap-allow-mixed';
				})
				.join('\n')
		});
	}

via: https://github.com/cordova-rtc/cordova-plugin-iosrtc/blob/master/js/RTCPeerConnection.js#L316

[ostap0207]

Thanks for the workaround!