Fix black video in calls, fixes #1002

This introduces multiple hacks to make things work:
1.) Rewrite jingle from/to peer to only contain VP8 codec. In particular
  we don't want to include error correcting pseudo-codecs like red, rtx etc.
2.) Use the video transceiver's setCodecPreferences() method to
  restrict to VP8, too. Also no error-correcting pseudo-codecs.
3.) Use uuid as stream id (not sure if this made any difference, though)

Author: tmolitor-stud-tu

Monal/Classes/AVCallUI.swift

@@ -72,7 +72,7 @@ struct AVCallUI: View {
     }
 
     func maybeStartRenderer() {
-        if !videoRenderingStarted && MLCallType(rawValue:call.callType) == .video && (MLCallState(rawValue:call.state) == .connecting || MLCallState(rawValue:call.state) == .connected) {
+        if !videoRenderingStarted && MLCallType(rawValue:call.callType) == .video && MLCallState(rawValue:call.state) == .connected {
             DDLogInfo("Starting local and remote video renderers...")
             //local video should be displayed as "mirrored", if front camera is used
             self.localRenderer.transform = CGAffineTransformMakeScale(cameraPosition == .front ? -1.0 : 1.0, 1.0)

Monal/Classes/MLCall.m

@@ -948,10 +948,10 @@ -(void) offerSDP
             self.encryptionState = MLCallEncryptionStateClear;
 
         XMPPIQ* sdpIQ = [[XMPPIQ alloc] initWithType:kiqSetType to:self.fullRemoteJid];
-        [sdpIQ addChildNode:[[MLXMLNode alloc] initWithElement:@"jingle" andNamespace:@"urn:xmpp:jingle:1" withAttributes:@{
+        [sdpIQ addChildNode:[self sanitizeJingleNode:[[MLXMLNode alloc] initWithElement:@"jingle" andNamespace:@"urn:xmpp:jingle:1" withAttributes:@{
             @"action": @"session-initiate",
             @"sid": self.jmiid,
-        } andChildren:children andData:nil]];
+        } andChildren:children andData:nil]]];
         @synchronized(self.candidateQueueLock) {
             self.localSDP = sdpIQ;
         }
@@ -1639,12 +1639,12 @@ -(void) processIncomingSDP:(NSNotification*) notification
         if([iqNode check:@"{urn:xmpp:jingle:1}jingle<action=session-accept>"])
         {
             type = @"answer";
-            rawSDP = [HelperTools xml2sdp:[iqNode findFirst:@"{urn:xmpp:jingle:1}jingle"] withInitiator:NO];
+            rawSDP = [HelperTools xml2sdp:[self sanitizeJingleNode:[iqNode findFirst:@"{urn:xmpp:jingle:1}jingle"]] withInitiator:NO];
         }
         else if([iqNode check:@"{urn:xmpp:jingle:1}jingle<action=session-initiate>"])
         {
             type = @"offer";
-            rawSDP = [HelperTools xml2sdp:[iqNode findFirst:@"{urn:xmpp:jingle:1}jingle"] withInitiator:YES];
+            rawSDP = [HelperTools xml2sdp:[self sanitizeJingleNode:[iqNode findFirst:@"{urn:xmpp:jingle:1}jingle"]] withInitiator:YES];
         }
     }
     //handle session-terminate: fake jmi finish message and handle it
@@ -1758,10 +1758,10 @@ -(void) processIncomingSDP:(NSNotification*) notification
                     [self.account send:[[XMPPIQ alloc] initAsResponseTo:iqNode]];
 
                     XMPPIQ* sdpIQ = [[XMPPIQ alloc] initWithType:kiqSetType to:self.fullRemoteJid];
-                    [sdpIQ addChildNode:[[MLXMLNode alloc] initWithElement:@"jingle" andNamespace:@"urn:xmpp:jingle:1" withAttributes:@{
+                    [sdpIQ addChildNode:[self sanitizeJingleNode:[[MLXMLNode alloc] initWithElement:@"jingle" andNamespace:@"urn:xmpp:jingle:1" withAttributes:@{
                         @"action": @"session-accept",
                         @"sid": self.jmiid,
-                    } andChildren:children andData:nil]];
+                    } andChildren:children andData:nil]]];
                     [self.account send:sdpIQ];
 
                     @synchronized(self.candidateQueueLock) {
@@ -1884,4 +1884,17 @@ -(BOOL) decryptFingerprintsInIqNode:(XMPPIQ*) iqNode
     return retval;
 }
 
+-(MLXMLNode*) sanitizeJingleNode:(MLXMLNode*) jingleNode
+{
+    //modify jingle to only include VP8, VP9 and H264 codecs
+    //in particular this means: not having any error correction codecs: these cause black video streams
+    NSArray* allowedCodecs = @[@"VP8"];//, @"VP9", @"H264"];
+    MLXMLNode* sanitizedNode = [jingleNode copy];
+    for(MLXMLNode* videoNode in [sanitizedNode find:@"content/{urn:xmpp:jingle:apps:rtp:1}description<media=video>"])
+        for(MLXMLNode* payloadNode in [videoNode find:@"payload-type"])
+            if(![allowedCodecs containsObject:[payloadNode findFirst:@"/@name"]])
+                [videoNode removeChildNode:payloadNode];
+    return sanitizedNode;
+}
+
 @end

Monal/Classes/WebRTCClient.swift

@@ -32,7 +32,6 @@ final class WebRTCClient: NSObject {
     @objc public let peerConnection: RTCPeerConnection
     private let rtcAudioSession =  RTCAudioSession.sharedInstance()
     private let audioQueue = DispatchQueue(label: "audio")
-    private let streamId = "-"
     private var mediaConstrains: [String:String] = [:]
     private var videoCapturer: RTCVideoCapturer?
     private var localVideoTrack: RTCVideoTrack?
@@ -110,8 +109,8 @@ final class WebRTCClient: NSObject {
         self.peerConnection = peerConnection!
         super.init()
 
-        self.createMediaSenders(audioOnly: audioOnly)
         self.peerConnection.delegate = self
+        self.createMediaSenders(audioOnly: audioOnly)
 
         // see https://stackoverflow.com/a/43765394
         if audioOnly {
@@ -207,15 +206,30 @@ final class WebRTCClient: NSObject {
 
     @objc
     func renderRemoteVideo(to renderer: RTCVideoRenderer) {
+        DDLogInfo("Now rendering remote video to RTCVideoRenderer view...")
         self.remoteVideoTrack?.add(renderer)
     }
 
     @objc
     func addVideo() {
         let videoTrack = self.createVideoTrack()
         self.localVideoTrack = videoTrack
-        self.peerConnection.add(videoTrack, streamIds: [self.streamId])
-        self.remoteVideoTrack = self.peerConnection.transceivers.first { $0.mediaType == .video }?.receiver.track as? RTCVideoTrack
+        
+        self.peerConnection.add(videoTrack, streamIds: [UUID().uuidString])
+        let videoTransceiver = self.peerConnection.transceivers.first { $0.mediaType == .video }!
+//         let videoTransceiver = self.peerConnection.addTransceiver(of:.video, init:RTCRtpTransceiverInit())!
+//         videoTransceiver.sender.track = videoTrack
+        
+        let capabilities = WebRTCClient.factory.rtpSenderCapabilities(forKind: kRTCMediaStreamTrackKindVideo)
+        let codecs = capabilities.codecs
+        let preferredCodecs = codecs.filter { $0.name=="VP8" }
+        do {
+            try videoTransceiver.setCodecPreferences(preferredCodecs)
+        } catch {
+            DDLogError("Error setting codec preferences: \(String(describing:error))")
+        }
+        
+        self.remoteVideoTrack = videoTransceiver.receiver.track as? RTCVideoTrack
     }
 
     @objc
@@ -236,7 +250,10 @@ final class WebRTCClient: NSObject {
     private func createMediaSenders(audioOnly: Bool) {
         //Audio
         let audioTrack = self.createAudioTrack()
-        self.peerConnection.add(audioTrack, streamIds: [self.streamId])
+        
+//         let audioTransceiver = self.peerConnection.addTransceiver(of:.audio, init:RTCRtpTransceiverInit())
+//         audioTransceiver?.sender.track = audioTrack
+        self.peerConnection.add(audioTrack, streamIds: [UUID().uuidString])
 
         //Video
         if !audioOnly {
@@ -313,10 +330,14 @@ extension WebRTCClient: RTCPeerConnectionDelegate {
 
     func peerConnection(_ peerConnection: RTCPeerConnection, didAdd stream: RTCMediaStream) {
         DDLogDebug("peerConnection did add stream")
+//         self.remoteVideoTrack = stream.videoTracks.first(where: { $0 is RTCVideoTrack }) as? RTCVideoTrack
     }
 
     func peerConnection(_ peerConnection: RTCPeerConnection, didRemove stream: RTCMediaStream) {
         DDLogDebug("peerConnection did remove stream")
+//         if stream.videoTracks.first(where: { $0.trackId == self.remoteVideoTrack?.trackId }) != nil {
+//             self.remoteVideoTrack = nil
+//         }
     }
 
     func peerConnectionShouldNegotiate(_ peerConnection: RTCPeerConnection) {