Added the API to create an RTCRtpSender to the Objective C wrapper.

Objective C applications can now create new RTCRtpSenders and change their tracks, which gives them more fine grained control than MediaStreams.

BUG=

Review-Url: https://codereview.webrtc.org/1888633002
Cr-Commit-Position: refs/heads/master@{#12570}

webrtc/examples/objc/AppRTCDemo/ARDAppClient.m

@@ -22,6 +22,7 @@
 #import "WebRTC/RTCMediaConstraints.h"
 #import "WebRTC/RTCMediaStream.h"
 #import "WebRTC/RTCPeerConnectionFactory.h"
+#import "WebRTC/RTCRtpSender.h"
 
 #import "ARDAppEngineClient.h"
 #import "ARDCEODTURNClient.h"
@@ -48,6 +49,9 @@ static NSInteger const kARDAppClientErrorCreateSDP = -3;
 static NSInteger const kARDAppClientErrorSetSDP = -4;
 static NSInteger const kARDAppClientErrorInvalidClient = -5;
 static NSInteger const kARDAppClientErrorInvalidRoom = -6;
+static NSString * const kARDMediaStreamId = @"ARDAMS";
+static NSString * const kARDAudioTrackId = @"ARDAMSa0";
+static NSString * const kARDVideoTrackId = @"ARDAMSv0";
 
 // TODO(tkchin): Remove guard once rtc_sdk_common_objc compiles on Mac.
 #if defined(WEBRTC_IOS)
@@ -505,9 +509,9 @@ static BOOL const kARDAppClientEnableTracing = NO;
   _peerConnection = [_factory peerConnectionWithConfiguration:config
                                                   constraints:constraints
                                                      delegate:self];
-  // Create AV media stream and add it to the peer connection.
-  RTCMediaStream *localStream = [self createLocalMediaStream];
-  [_peerConnection addStream:localStream];
+  // Create AV senders.
+  [self createAudioSender];
+  [self createVideoSender];
   if (_isInitiator) {
     // Send offer.
     __weak ARDAppClient *weakSelf = self;
@@ -606,17 +610,25 @@ static BOOL const kARDAppClientEnableTracing = NO;
   }
 }
 
-- (RTCMediaStream *)createLocalMediaStream {
-  RTCMediaStream *localStream = [_factory mediaStreamWithStreamId:@"ARDAMS"];
-  RTCVideoTrack *localVideoTrack = [self createLocalVideoTrack];
-  if (localVideoTrack) {
-    [localStream addVideoTrack:localVideoTrack];
-    [_delegate appClient:self didReceiveLocalVideoTrack:localVideoTrack];
+- (RTCRtpSender *)createVideoSender {
+  RTCRtpSender *sender =
+      [_peerConnection senderWithKind:kRTCMediaStreamTrackKindVideo
+                             streamId:kARDMediaStreamId];
+  RTCVideoTrack *track = [self createLocalVideoTrack];
+  if (track) {
+    sender.track = track;
+    [_delegate appClient:self didReceiveLocalVideoTrack:track];
   }
-  RTCAudioTrack *localAudioTrack =
-      [_factory audioTrackWithTrackId:@"ARDAMSa0"];
-  [localStream addAudioTrack:localAudioTrack];
-  return localStream;
+  return sender;
+}
+
+- (RTCRtpSender *)createAudioSender {
+  RTCRtpSender *sender =
+      [_peerConnection senderWithKind:kRTCMediaStreamTrackKindAudio
+                             streamId:kARDMediaStreamId];
+  RTCAudioTrack *track = [_factory audioTrackWithTrackId:kARDAudioTrackId];
+  sender.track = track;
+  return sender;
 }
 
 - (RTCVideoTrack *)createLocalVideoTrack {
@@ -634,7 +646,7 @@ static BOOL const kARDAppClientEnableTracing = NO;
         [_factory avFoundationVideoSourceWithConstraints:mediaConstraints];
     localVideoTrack =
         [_factory videoTrackWithSource:source
-                               trackId:@"ARDAMSv0"];
+                               trackId:kARDVideoTrackId];
   }
 #endif
   return localVideoTrack;

webrtc/sdk/objc/Framework/Classes/RTCMediaStreamTrack.mm

@@ -12,6 +12,11 @@
 
 #import "NSString+StdString.h"
 
+NSString * const kRTCMediaStreamTrackKindAudio =
+    @(webrtc::MediaStreamTrackInterface::kAudioKind);
+NSString * const kRTCMediaStreamTrackKindVideo =
+    @(webrtc::MediaStreamTrackInterface::kVideoKind);
+
 @implementation RTCMediaStreamTrack {
   rtc::scoped_refptr<webrtc::MediaStreamTrackInterface> _nativeTrack;
   RTCMediaStreamTrackType _type;

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm

@@ -311,6 +311,17 @@ void PeerConnectionDelegateAdapter::OnIceCandidate(
   _peerConnection->SetRemoteDescription(observer, sdp.nativeDescription);
 }
 
+- (RTCRtpSender *)senderWithKind:(NSString *)kind
+                        streamId:(NSString *)streamId {
+  std::string nativeKind = [NSString stdStringForString:kind];
+  std::string nativeStreamId = [NSString stdStringForString:streamId];
+  rtc::scoped_refptr<webrtc::RtpSenderInterface> nativeSender(
+      _peerConnection->CreateSender(nativeKind, nativeStreamId));
+  return nativeSender ?
+      [[RTCRtpSender alloc] initWithNativeRtpSender:nativeSender]
+      : nil;
+}
+
 - (NSArray<RTCRtpSender *> *)senders {
   std::vector<rtc::scoped_refptr<webrtc::RtpSenderInterface>> nativeSenders(
       _peerConnection->GetSenders());

webrtc/sdk/objc/Framework/Classes/RTCRtpSender.mm

@@ -10,8 +10,10 @@
 
 #import "RTCRtpSender+Private.h"
 
+#import "NSString+StdString.h"
 #import "RTCMediaStreamTrack+Private.h"
 #import "RTCRtpParameters+Private.h"
+#import "WebRTC/RTCLogging.h"
 
 #include "webrtc/api/mediastreaminterface.h"
 
@@ -21,19 +23,28 @@
 
 - (instancetype)initWithNativeRtpSender:
     (rtc::scoped_refptr<webrtc::RtpSenderInterface>)nativeRtpSender {
+  NSParameterAssert(nativeRtpSender);
   if (self = [super init]) {
     _nativeRtpSender = nativeRtpSender;
+    RTCLogInfo(@"RTCRtpSender(%p): created sender: %@", self, self.description);
   }
   return self;
 }
 
+- (NSString *)senderId {
+  return [NSString stringForStdString:_nativeRtpSender->id()];
+}
+
 - (RTCRtpParameters *)parameters {
   return [[RTCRtpParameters alloc]
       initWithNativeParameters:_nativeRtpSender->GetParameters()];
 }
 
-- (BOOL)setParameters:(RTCRtpParameters *)parameters {
-  return _nativeRtpSender->SetParameters(parameters.nativeParameters);
+- (void)setParameters:(RTCRtpParameters *)parameters {
+  if (!_nativeRtpSender->SetParameters(parameters.nativeParameters)) {
+    RTCLogError(@"RTCRtpSender(%p): Failed to set parameters: %@", self,
+        parameters);
+  }
 }
 
 - (RTCMediaStreamTrack *)track {
@@ -45,4 +56,15 @@
   return nil;
 }
 
+- (void)setTrack:(RTCMediaStreamTrack *)track {
+  if (!_nativeRtpSender->SetTrack(track.nativeTrack)) {
+    RTCLogError(@"RTCRtpSender(%p): Failed to set track %@", self, track);
+  }
+}
+
+- (NSString *)description {
+  return [NSString stringWithFormat:@"RTCRtpSender {\n  senderId: %@\n}",
+      self.senderId];
+}
+
 @end

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaStreamTrack.h

@@ -22,6 +22,9 @@ typedef NS_ENUM(NSInteger, RTCMediaStreamTrackState) {
 
 NS_ASSUME_NONNULL_BEGIN
 
+RTC_EXTERN NSString * const kRTCMediaStreamTrackKindAudio;
+RTC_EXTERN NSString * const kRTCMediaStreamTrackKindVideo;
+
 RTC_EXPORT
 @interface RTCMediaStreamTrack : NSObject
 

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h

@@ -171,6 +171,16 @@ RTC_EXPORT
 
 @end
 
+@interface RTCPeerConnection (Media)
+
+/**
+ * Create an RTCRtpSender with the specified kind and media stream ID.
+ * See RTCMediaStreamTrack.h for available kinds.
+ */
+- (RTCRtpSender *)senderWithKind:(NSString *)kind streamId:(NSString *)streamId;
+
+@end
+
 @interface RTCPeerConnection (DataChannel)
 
 /** Create a new data channel with the given label and configuration. */

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCRtpSender.h

@@ -19,22 +19,20 @@ NS_ASSUME_NONNULL_BEGIN
 RTC_EXPORT
 @protocol RTCRtpSender <NSObject>
 
+/** A unique identifier for this sender. */
+@property(nonatomic, readonly) NSString *senderId;
+
 /** The currently active RTCRtpParameters, as defined in
  *  https://www.w3.org/TR/webrtc/#idl-def-RTCRtpParameters.
  */
-@property(nonatomic, readonly) RTCRtpParameters *parameters;
+@property(nonatomic, copy) RTCRtpParameters *parameters;
 
 /** The RTCMediaStreamTrack associated with the sender.
  *  Note: reading this property returns a new instance of
  *  RTCMediaStreamTrack. Use isEqual: instead of == to compare
  *  RTCMediaStreamTrack instances.
  */
-@property(nonatomic, readonly) RTCMediaStreamTrack *track;
-
-/** Set the new RTCRtpParameters to be used by the sender.
- *  Returns YES if the new parameters were applied, NO otherwise.
- */
-- (BOOL)setParameters:(RTCRtpParameters *)parameters;
+@property(nonatomic, copy, nullable) RTCMediaStreamTrack *track;
 
 @end