Simulcast support for iOS SDK

Original credit: https://github.com/shiguredo-webrtc-build/webrtc-build/blob/master/patches/ios_simulcast.patch

sdk/BUILD.gn

@@ -647,6 +647,7 @@ if (is_ios || is_mac) {
 
       deps = [
         ":av1",
+        ":simulcast",
         ":base_objc",
         ":native_video",
         ":videocodec_objc",
@@ -724,6 +725,22 @@ if (is_ios || is_mac) {
       ]
     }
 
+    rtc_library("simulcast") {
+      sources = [
+        "objc/components/video_codec/RTCVideoEncoderFactorySimulcast.h",
+        "objc/components/video_codec/RTCVideoEncoderFactorySimulcast.mm",
+        "objc/api/video_codec/RTCVideoEncoderSimulcast.h",
+        "objc/api/video_codec/RTCVideoEncoderSimulcast.mm",
+      ]
+
+      deps = [
+        ":base_objc",
+        ":wrapped_native_codec_objc",
+        "../media:rtc_media_base",
+        "../media:rtc_simulcast_encoder_adapter",
+      ]
+    }
+
     # Build the PeerConnectionFactory without audio/video support.
     # This target depends on the objc_peeerconnectionfactory_base which still
     # includes some audio/video related objects such as RTCAudioSource because
@@ -1239,6 +1256,7 @@ if (is_ios || is_mac) {
           "objc/components/video_codec/RTCVideoDecoderH264.h",
           "objc/components/video_codec/RTCVideoEncoderFactoryH264.h",
           "objc/components/video_codec/RTCVideoEncoderH264.h",
+          "objc/components/video_codec/RTCVideoEncoderFactorySimulcast.h",
           "objc/components/video_frame_buffer/RTCCVPixelBuffer.h",
           "objc/helpers/RTCCameraPreviewView.h",
           "objc/helpers/RTCDispatcher.h",
@@ -1285,6 +1303,7 @@ if (is_ios || is_mac) {
           "objc/api/video_codec/RTCVideoEncoderVP8.h",
           "objc/api/video_codec/RTCVideoEncoderVP9.h",
           "objc/api/video_codec/RTCVideoEncoderAV1.h",
+          "objc/api/video_codec/RTCVideoEncoderSimulcast.h",
           "objc/api/video_frame_buffer/RTCNativeI420Buffer.h",
           "objc/api/video_frame_buffer/RTCNativeMutableI420Buffer.h",
         ]

sdk/objc/api/video_codec/RTCVideoEncoderSimulcast.h

@@ -0,0 +1,13 @@
+#import "RTCMacros.h"
+#import "RTCVideoEncoder.h"
+#import "RTCVideoEncoderFactory.h"
+#import "RTCVideoCodecInfo.h"
+
+RTC_OBJC_EXPORT
+@interface RTC_OBJC_TYPE (RTCVideoEncoderSimulcast) : NSObject
+
++ (id<RTC_OBJC_TYPE(RTCVideoEncoder)>)simulcastEncoderWithPrimary:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)primary
+                                                         fallback:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)fallback
+                                                   videoCodecInfo:(RTC_OBJC_TYPE(RTCVideoCodecInfo) *)videoCodecInfo;
+
+@end

sdk/objc/api/video_codec/RTCVideoEncoderSimulcast.mm

@@ -0,0 +1,26 @@
+#import <Foundation/Foundation.h>
+
+#import "RTCMacros.h"
+#import "RTCVideoEncoderSimulcast.h"
+#import "RTCWrappedNativeVideoEncoder.h"
+#import "api/peerconnection/RTCVideoCodecInfo+Private.h"
+
+#include "native/api/video_encoder_factory.h"
+#include "media/engine/simulcast_encoder_adapter.h"
+
+@implementation RTC_OBJC_TYPE (RTCVideoEncoderSimulcast)
+
++ (id<RTC_OBJC_TYPE(RTCVideoEncoder)>)simulcastEncoderWithPrimary:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)primary
+                                                         fallback:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)fallback
+                                                   videoCodecInfo:(RTC_OBJC_TYPE(RTCVideoCodecInfo) *)videoCodecInfo {
+    auto nativePrimary = webrtc::ObjCToNativeVideoEncoderFactory(primary);
+    auto nativeFallback = webrtc::ObjCToNativeVideoEncoderFactory(fallback);
+    auto nativeFormat = [videoCodecInfo nativeSdpVideoFormat];
+    return [[RTC_OBJC_TYPE(RTCWrappedNativeVideoEncoder) alloc]
+        initWithNativeEncoder: std::make_unique<webrtc::SimulcastEncoderAdapter>(
+            nativePrimary.release(),
+            nativeFallback.release(),
+            std::move(nativeFormat))];
+}
+
+@end

sdk/objc/components/video_codec/RTCVideoEncoderFactorySimulcast.h

@@ -0,0 +1,16 @@
+#import <Foundation/Foundation.h>
+
+#import "RTCMacros.h"
+#import "RTCVideoEncoderFactory.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+RTC_OBJC_EXPORT
+@interface RTC_OBJC_TYPE (RTCVideoEncoderFactorySimulcast) : NSObject <RTC_OBJC_TYPE(RTCVideoEncoderFactory)>
+
+- (instancetype)initWithPrimary:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)primary
+                       fallback:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)fallback;
+
+@end
+
+NS_ASSUME_NONNULL_END

sdk/objc/components/video_codec/RTCVideoEncoderFactorySimulcast.mm

@@ -0,0 +1,39 @@
+#import <Foundation/Foundation.h>
+
+#import "RTCMacros.h"
+#import "RTCVideoCodecInfo.h"
+#import "RTCVideoEncoderFactorySimulcast.h"
+#import "api/video_codec/RTCVideoEncoderSimulcast.h"
+
+@interface RTC_OBJC_TYPE (RTCVideoEncoderFactorySimulcast) ()
+
+@property id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)> primary;
+@property id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)> fallback;
+
+@end
+
+
+@implementation RTC_OBJC_TYPE (RTCVideoEncoderFactorySimulcast)
+
+@synthesize primary = _primary;
+@synthesize fallback = _fallback;
+
+- (instancetype)initWithPrimary:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)primary
+                       fallback:(id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)fallback {
+    if (self = [super init]) {
+        _primary = primary;
+        _fallback = fallback;
+    }
+    return self;
+}
+
+- (nullable id<RTC_OBJC_TYPE(RTCVideoEncoder)>)createEncoder: (RTC_OBJC_TYPE(RTCVideoCodecInfo) *)info {
+    return [RTCVideoEncoderSimulcast simulcastEncoderWithPrimary: _primary fallback: _fallback videoCodecInfo: info];
+}
+
+- (NSArray<RTC_OBJC_TYPE(RTCVideoCodecInfo) *> *)supportedCodecs {
+    return [[_primary supportedCodecs] arrayByAddingObjectsFromArray: [_fallback supportedCodecs]];
+}
+
+
+@end