From 87b8c9b9ba05b2a4b3094de2b8700733da80980c Mon Sep 17 00:00:00 2001
From: Luke Bermingham <Luke.Bermingham@xa.epicgames.com>
Date: Sun, 10 Sep 2023 19:53:23 -0400
Subject: [PATCH] Bugfix: LiveLink App had two datachannels, one it created and
 one that was automatically created as part of the request from the UE side.
 Fix is to remove manual creation of the datachannel on the LiveLink app side.

#rb Brian.Smith
#jira UE-194903

[CL 27744198 by Luke Bermingham in ue5-main branch]
---
 .../vcam/WebRTC/Services/WebRTCClient.swift   | 21 ++++++-------------
 .../vcam/WebRTCStreamingConnection.swift      |  2 ++
 2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTC/Services/WebRTCClient.swift b/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTC/Services/WebRTCClient.swift
index 601111b402d2..34b30c660a54 100644
--- a/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTC/Services/WebRTCClient.swift
+++ b/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTC/Services/WebRTCClient.swift
@@ -61,12 +61,6 @@ final class WebRTCClient: NSObject {
         
         self.peerConnection = pc
         
-        // Create the data channel
-        if let dataChannel = createDataChannel(peerConnection: pc) {
-            dataChannel.delegate = self
-            self.dataChannel = dataChannel
-        }
-        
         self.configureAudioSession()
         self.peerConnection!.delegate = self
     }
@@ -178,15 +172,6 @@ final class WebRTCClient: NSObject {
 // MARK: Data Channels
 extension WebRTCClient: RTCDataChannelDelegate {
     
-    private func createDataChannel(peerConnection : RTCPeerConnection) -> RTCDataChannel? {
-        let config = RTCDataChannelConfiguration()
-        guard let dataChannel = peerConnection.dataChannel(forLabel: "iOSDataChannel", configuration: config) else {
-            debugPrint("Warning: Couldn't create data channel.")
-            return nil
-        }
-        return dataChannel
-    }
-    
     func sendData(_ data: Data) {
         let buffer = RTCDataBuffer(data: data, isBinary: true)
         self.dataChannel?.sendData(buffer)
@@ -239,6 +224,12 @@ extension WebRTCClient: RTCPeerConnectionDelegate {
     
     func peerConnection(_ peerConnection: RTCPeerConnection, didOpen dataChannel: RTCDataChannel) {
         debugPrint("peerConnection did open data channel")
+        
+        // Store datachannel internally for message sending and set datachannel delegate so we can react to its events
+        dataChannel.delegate = self
+        self.dataChannel = dataChannel
+        
+        // Send the device resolution over the datachannel
         self.sendDeviceResolution()
     }
     
diff --git a/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTCStreamingConnection.swift b/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTCStreamingConnection.swift
index 716be564ca81..38aa8e28c3de 100644
--- a/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTCStreamingConnection.swift
+++ b/Engine/Extras/VirtualProduction/LiveLinkVCAM/vcam/WebRTCStreamingConnection.swift
@@ -582,6 +582,8 @@ extension WebRTCStreamingConnection: WebRTCClientDelegate {
                 case .LatencyTest:
                     fallthrough
                 case .InitialSettings:
+                    // Do nothing with initial settings, but use it to send device resolution as this is a convenient time as we are guaranteed datachannel is working
+                    self.webRTCClient?.sendDeviceResolution()
                     fallthrough
                 case .FileExtension:
                     fallthrough