Support for simulcast in Android SDK

Adapted from Shiguredo's patch https://github.com/shiguredo-webrtc-build/webrtc-build/blob/master/patches/android_simulcast.patch

sdk/android/BUILD.gn

@@ -520,6 +520,8 @@ if (is_android) {
     sources = [
       "api/org/webrtc/SoftwareVideoDecoderFactory.java",
       "api/org/webrtc/SoftwareVideoEncoderFactory.java",
+      "api/org/webrtc/SimulcastVideoEncoder.java",
+      "api/org/webrtc/SimulcastVideoEncoderFactory.java",
     ]
 
     deps = [
@@ -854,13 +856,29 @@ if (current_os == "linux" || is_android) {
     ]
   }
 
+  rtc_library("simulcast_jni") {
+    visibility = [ "*" ]
+    allow_poison = [ "software_video_codecs" ]
+    sources = [
+      "src/jni/simulcast_video_encoder.cc",
+      "src/jni/simulcast_video_encoder.h"
+    ]
+    deps = [
+      ":base_jni",
+      ":video_jni",
+      ":native_api_codecs",
+      "../../media:rtc_simulcast_encoder_adapter"
+    ]
+  }
+
   rtc_library("swcodecs_jni") {
     visibility = [ "*" ]
     allow_poison = [ "software_video_codecs" ]
     deps = [
       ":libaom_av1_jni",
       ":libvpx_vp8_jni",
       ":libvpx_vp9_jni",
+      ":simulcast_jni",
     ]
   }
 

sdk/android/api/org/webrtc/SimulcastVideoEncoder.java

@@ -0,0 +1,28 @@
+package org.webrtc;
+
+public class SimulcastVideoEncoder extends WrappedNativeVideoEncoder {
+
+    static native long nativeCreateEncoder(VideoEncoderFactory primary, VideoEncoderFactory fallback, VideoCodecInfo info);
+
+    VideoEncoderFactory primary;
+    VideoEncoderFactory fallback;
+    VideoCodecInfo info;
+
+    public SimulcastVideoEncoder(VideoEncoderFactory primary, VideoEncoderFactory fallback, VideoCodecInfo info) {
+        this.primary = primary;
+        this.fallback = fallback;
+        this.info = info;
+    }
+
+    @Override
+    public long createNativeVideoEncoder() {
+        return nativeCreateEncoder(primary, fallback, info);
+    }
+
+    @Override
+    public boolean isHardwareEncoder() {
+        return false;
+    }
+
+}
+

sdk/android/api/org/webrtc/SimulcastVideoEncoderFactory.java

@@ -0,0 +1,43 @@
+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+import android.support.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Arrays;
+
+public class SimulcastVideoEncoderFactory implements VideoEncoderFactory {
+
+    VideoEncoderFactory primary;
+    VideoEncoderFactory fallback;
+
+    public SimulcastVideoEncoderFactory(VideoEncoderFactory primary, VideoEncoderFactory fallback) {
+        this.primary = primary;
+        this.fallback = fallback;
+    }
+
+    @Nullable
+    @Override
+    public VideoEncoder createEncoder(VideoCodecInfo info) {
+        return new SimulcastVideoEncoder(primary, fallback, info);
+    }
+
+    @Override
+    public VideoCodecInfo[] getSupportedCodecs() {
+        List<VideoCodecInfo> codecs = new ArrayList<VideoCodecInfo>();
+        codecs.addAll(Arrays.asList(primary.getSupportedCodecs()));
+        codecs.addAll(Arrays.asList(fallback.getSupportedCodecs()));
+        return codecs.toArray(new VideoCodecInfo[codecs.size()]);
+    }
+
+}

sdk/android/src/jni/simulcast_video_encoder.cc

@@ -0,0 +1,34 @@
+#include <jni.h>
+
+#include "sdk/android/src/jni/jni_helpers.h"
+#include "sdk/android/src/jni/video_encoder_factory_wrapper.h"
+#include "sdk/android/src/jni/video_codec_info.h"
+#include "sdk/android/native_api/codecs/wrapper.h"
+#include "media/engine/simulcast_encoder_adapter.h"
+#include "rtc_base/logging.h"
+
+using namespace webrtc;
+using namespace webrtc::jni;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// (VideoEncoderFactory primary, VideoEncoderFactory fallback, VideoCodecInfo info)
+JNIEXPORT jlong JNICALL Java_org_webrtc_SimulcastVideoEncoder_nativeCreateEncoder(JNIEnv *env, jclass klass, jobject primary, jobject fallback, jobject info) {
+    RTC_LOG(LS_INFO) << "Create simulcast video encoder";
+    JavaParamRef<jobject> info_ref(info);
+    SdpVideoFormat format = VideoCodecInfoToSdpVideoFormat(env, info_ref);
+
+    // TODO: 影響は軽微だが、リークする可能性があるので将来的に修正したい
+    // https://github.com/shiguredo-webrtc-build/webrtc-build/pull/16#pullrequestreview-600675795
+    return NativeToJavaPointer(std::make_unique<SimulcastEncoderAdapter>(
+			    JavaToNativeVideoEncoderFactory(env, primary).release(),
+			    JavaToNativeVideoEncoderFactory(env, fallback).release(),
+			    format).release());
+}
+
+
+#ifdef __cplusplus
+}
+#endif