安卓mediasoup webrtc h264 编解码相关源码分析

Posted 2022-02-01 清霜之辰

文章目录

• 安卓mediasoup webrtc h264 编解码相关源码分析
• • • • mediasoup H264 支持
      • 安卓 webrtc 视频采集流程源码分析
      • 安卓 mediasoup 为啥没有使用H264硬编解码
      • mediasoup-client-android 中 VideoStreamEncoder 初始化
      • webrtc 中 VideoStreamEncoder 初始化
      • 解码器 H264Encoder 创建
      • mediasoup H264Encoder 初始化
      • webrtc H264Encoder 初始化
      • webrtc H264Decoder初始化流程
      • openh264 提供编解码相关函数
      • webrtc 视频 H264 硬编码

安卓mediasoup webrtc h264 编解码相关源码分析

本文首发地址 https://blog.csdn.net/CSqingchen/article/details/120218923
最新更新地址 https://gitee.com/chenjim/chenjimblog
本文基于libmediasoupclient 3.2.0 和 webrtc branch-heads/4147（m84）
本文得熟悉相关基础，参考 文1 和 文2

mediasoup H264 支持

• 打开 rtc_use_h264
  在 webrtc.gni 中可以看到如下，也就是安卓默认不支持 h264
  rtc_use_h264 = proprietary_codecs && !is_android && !is_ios && !(is_win && !is_clang)
  可以将此处改为 true ，也可以带上编译参数 'rtc_use_h264=true,如下：
  ./tools_webrtc/android/build_aar.py --extra-gn-args 'rtc_use_h264=true'

• mediasoup-demo-android 的 forceH264
  通过代码我们看到，这个参数只在 UrlFactory.java 中拼接地址使用
  正常情况 如果 url 中 有forceH264=true, 就应该采用H264编码
  如浏览器输入 https://v3demo.mediasoup.org/?forceH264=true&roomId=123456 输出的视频就是H264
  （安卓默认显示黑屏，缺少H264解码器，另文 解决）
  但是 mediasoup-demo-android 菜单勾选forceH264了还是 VP8 编码，算是个BUG …

---

安卓 webrtc 视频采集流程源码分析

webrtc针对视频采集对外主要提供的是VideoCapturer接口，实现类有ScreenCapturerAndroid、FileVideoCapturer和CameraCapturer，分别表示屏幕、文件、摄像头三种不同的视频来源，因为android系统先后提供了camera1.0和camera2.0接口，因此CameraCapturer又用Camera1Capturer和Camera2Capturer两个子类分别表示。
主要类图

视频采集和分发流程如下图

更多细节可以参考原文 webrtc源码分析之视频采集之一, 感谢 Jimmy2012

---

安卓 mediasoup 为啥没有使用H264硬编解码

1. 安卓 mediasoup Java层 CreateMediaEngine 如下
   mediasoup-demo-android\\app\\src\\main\\java\\org\\mediasoup\\droid\\lib\\PeerConnectionUtils.java 中

    VideoEncoderFactory encoderFactory = new DefaultVideoEncoderFactory( mEglBase.getEglBaseContext(), true /* enableIntelVp8Encoder */, true);
    VideoDecoderFactory decoderFactory = new DefaultVideoDecoderFactory(mEglBase.getEglBaseContext());
    mPeerConnectionFactory = builder.setAudioDeviceModule(adm)
            .setVideoEncoderFactory(encoderFactory)
            .setVideoDecoderFactory(decoderFactory)
            .createPeerConnectionFactory();

大致跟 AppRTCDemo PeerConnectionClient.java 相同，AppRTCDemo 支持H264软硬编解码，
其中 .createPeerConnectionFactory(); 相关流程如下

--> createPeerConnectionFactory()  
--> JNI_PeerConnectionFactory_CreatePeerConnectionFactory(...)   
(webrtc/src/sdk/android/src/jni/pc/peer_connection_factory.cc)   
--> CreatePeerConnectionFactoryForJava(...) (webrtc/src/sdk/android/src/jni/pc/peer_connection_factory.cc) 

CreatePeerConnectionFactoryForJava(...)
  media_dependencies.task_queue_factory = dependencies.task_queue_factory.get();
  media_dependencies.adm = std::move(audio_device_module);
  media_dependencies.audio_encoder_factory = std::move(audio_encoder_factory);
  media_dependencies.audio_decoder_factory = std::move(audio_decoder_factory);
  media_dependencies.audio_processing = std::move(audio_processor);
   //分别是PeerConnectionUtils.java 传入的 encoderFactory 和 decoderFactory  
  media_dependencies.video_encoder_factory = absl::WrapUnique(CreateVideoEncoderFactory(jni, jencoder_factory));
  media_dependencies.video_decoder_factory = absl::WrapUnique(CreateVideoDecoderFactory(jni, jdecoder_factory));
  dependencies.media_engine = cricket::CreateMediaEngine(std::move(media_dependencies));
 

2. 安卓 mediasoup Native 层 CreateMediaEngine 如下

Handler::GetNativeRtpCapabilities (libmediasoupclient/src/Device.cpp)  
-->  std::unique_ptr<PeerConnection> pc(new PeerConnection(privateListener.get(), peerConnectionOptions))  
(libmediasoupclient/src/Handler.cpp)  
-->  webrtc::CreateBuiltinVideoEncoderFactory  (libmediasoupclient/src/PeerConnection.cpp)  
-->  webrtc::CreatePeerConnectionFactory 
-->  cricket::CreateMediaEngine(std::move(media_dependencies))  (webrtc/src/api/create_peerconnection_factory.cc)
-->  CreateMediaEngine  (webrtc/src/media/engine/webrtc_media_engine.cc)
-->  WebRtcVideoEngine::WebRtcVideoEngine  (webrtc/src/media/engine/webrtc_media_engine.cc)

从 libmediasoupclient/src/PeerConnection.cpp 中 PeerConnection 构造函数部分代码如下，我们可以看到音视频编解码器的创建工厂

  this->peerConnectionFactory = webrtc::CreatePeerConnectionFactory(
    this->networkThread.get(),
    this->workerThread.get(),
    this->signalingThread.get(),
    nullptr /*default_adm*/,
    webrtc::CreateBuiltinAudioEncoderFactory(),
    webrtc::CreateBuiltinAudioDecoderFactory(),
    webrtc::CreateBuiltinVideoEncoderFactory(),
    webrtc::CreateBuiltinVideoDecoderFactory(),
    nullptr /*audio_mixer*/,
    nullptr /*audio_processing*/);

这里的 CreateBuiltin...Factory 也传到 CreateMediaEngine
从上面 1 2 可以看到 CreateMediaEngine 传入了不同的 Factory，而且实际编解码使用的是后者，参见后文

---

mediasoup-client-android 中 VideoStreamEncoder 初始化

后文前提是已经能够 使用H264软编码
调用堆栈如下

private void onNewConsumer(...)  (org.mediasoup.droid.lib.RoomClient.java)
-->  public Consumer consume(...)  (org.mediasoup.droid.RecvTransport.java)  
-->  Java_org_mediasoup_droid_RecvTransport_nativeConsume   (mediasoup-client-android\\mediasoup-client\\src\\main\\jni\\transport_jni.cpp)   
-->  Consumer* RecvTransport::Consume(...)  (libmediasoupclient/src/Transport.cpp）    
-->  RecvHandler::RecvResult RecvHandler::Receive(...)  (libmediasoupclient/src/Handler.cpp)   
-->  this->pc->SetRemoteDescription(PeerConnection::SdpType::OFFER, offer)    
-->  PeerConnection::SetRemoteDescription(...)    (webrtc/src/pc/peer_connection.cc)   
-->  PeerConnection::DoSetRemoteDescription(...)
-->  PeerConnection::ApplyRemoteDescription(...) 
-->  PeerConnection::UpdateSessionState(...)  
-->  PeerConnection::PushdownMediaDescription(...)    
-->  BaseChannel::SetRemoteContent(...)    (webrtc/src/pc/channel.cc)   
-->  VoiceChannel::SetRemoteContent_w(...)
-->  WebRtcVideoChannel::SetSendParameters  (webrtc/src/media/engine/webrtc_video_engine.cc)  
-->  WebRtcVideoChannel::ApplyChangedParams(...) 
-->  WebRtcVideoChannel::WebRtcVideoSendStream::SetSendParameters(...)   
-->  WebRtcVideoChannel::WebRtcVideoSendStream::SetCodec(..)  
-->  WebRtcVideoChannel::WebRtcVideoSendStream::RecreateWebRtcStream(...)  
-->  webrtc::VideoSendStream* Call::CreateVideoSendStream(,)  (webrtc/src/call/call.cc)  
-->  webrtc::VideoSendStream* Call::CreateVideoSendStream(,,) 
-->  VideoSendStream::VideoSendStream(..)  (webrtc/src/video/video_send_stream.cc)  
-->  std::unique_ptr<VideoStreamEncoderInterface> CreateVideoStreamEncoder(..) (webrtc/src/api/video/video_stream_encoder_create.cc)
-->  VideoStreamEncoder::VideoStreamEncoder(...)  (webrtc/src/video/video_stream_encoder.cc)  

---

webrtc 中 VideoStreamEncoder 初始化

这里基于应用 AppRTCDemo，并在应用中开启H264编解码，相关调用堆栈及说明如下

onCreateSuccess()   (src/main/java/org/appspot/apprtc/PeerConnectionClient.java)  
-->  peerConnection.setLocalDescription(sdpObserver, newDesc)   
-->  Java_org_webrtc_PeerConnection_nativeSetLocalDescription(...)   
(./out/release-build/arm64-v8a/gen/sdk/android/generated_peerconnection_jni/PeerConnection_jni.h)   
-->  PeerConnection::SetLocalDescription (pc/peer_connection.cc)
-->  PeerConnection::DoSetLocalDescription 
-->  PeerConnection::ApplyLocalDescription 
-->  PeerConnection::UpdateSessionState 
-->  PeerConnection::PushdownMediaDescription()  (pc/peer_connection.cc)
-->  BaseChannel::SetLocalContent()   (pc/channel.cc)    
-->  VideoChannel::SetLocalContent_w(...)
-->  BaseChannel::UpdateLocalStreams_w(..)    
-->  WebRtcVideoChannel::AddSendStream(..)      (media/engine/webrtc_video_engine.cc)  
-->  WebRtcVideoChannel::WebRtcVideoSendStream::WebRtcVideoSendStream(..)  
-->  WebRtcVideoChannel::WebRtcVideoSendStream::SetCodec(..)  
-->  WebRtcVideoChannel::WebRtcVideoSendStream::RecreateWebRtcStream()  
-->  webrtc::VideoSendStream* Call::CreateVideoSendStream(..)  (call/call.cc)   
-->  VideoSendStream::VideoSendStream(..)   (video/video_send_stream.cc)   
-->  std::unique_ptr<VideoStreamEncoderInterface> CreateVideoStreamEncoder(..)  (api/video/video_stream_encoder_create.cc)  
-->  VideoStreamEncoder::VideoStreamEncoder()   (video/video_stream_encoder.cc)   

从上面两小节可以看到：mediasoup 和 webrtc VideoStreamEncoder 创建有稍微差别

---

解码器 H264Encoder 创建

视频帧分发 到

VideoStreamEncoder::OnFrame (webrtc/src/video/video_stream_encoder.cc)    
-->  VideoStreamEncoder::ReconfigureEncoder()   
-->  encoder_ = settings_.encoder_factory->CreateVideoEncoder(encoder_config_.video_format)    
  (webrtc/src/video/video_stream_encoder.cc)  
//这里的 `settings_` 是在上步创建时赋值，会影响后续 `Encode` 的创建        

• 如下是 mediasoup 中 H264 Encode 的调用栈堆

-->  internal_encoder = std::make_unique<EncoderSimulcastProxy>(internal_encoder_factory_.get(), format)   (webrtc\\src\\api\\video_codecs\\builtin_video_encoder_factory.cc)   
-->  EncoderSimulcastProxy::EncoderSimulcastProxy (webrtc\\src\\media\\engine\\encoder_simulcast_proxy.cc)   
-->  InternalEncoderFactory::CreateVideoEncoder (webrtc/src/media/engine/internal_encoder_factory.cc)  
-->  H264Encoder::Create()  (webrtc/src/modules/video_coding/codecs/h264/h264.cc)   
-->  H264EncoderImpl::H264EncoderImpl  (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl.cc)  

• 如下是 webrtc AppRTCDemo 中 调用栈堆

-->  VideoEncoderFactoryWrapper::CreateVideoEncoder (sdk/android/src/jni/video_encoder_factory_wrapper.cc)
-->  Java_VideoEncoderFactory_createEncoder()  (./out/release-build/arm64-v8a/gen/sdk/android/generated_video_jni/VideoEncoderFactory_jni.h)  
//这里会调用Java层代码 VideoEncoderFactory 的 createEncoder(..)
//我在应用中开启了硬编码和H264 Base编解码，所以 DefaultVideoEncoderFactory 是 VideoEncoderFactory 的实现,进而返回 VideoEncoderFallback (...)
--> VideoEncoderFallback(VideoEncoder fallback, VideoEncoder primary)   
(sdk/android/api/org/webrtc/VideoEncoderFallback.java)  
--> public long createNativeVideoEncoder()   (sdk/android/api/org/webrtc/VideoEncoderFallback.java)  
--> JNI_VideoEncoderFallback_CreateEncoder(...) (sdk/android/src/jni/video_encoder_fallback.cc) 
--> CreateVideoEncoderSoftwareFallbackWrapper()  (api/video_codecs/video_encoder_software_fallback_wrapper.cc)  
//VideoEncoderSoftwareFallbackWrapper 是最终的 Encode 
--> VideoEncoderSoftwareFallbackWrapper::VideoEncoderSoftwareFallbackWrapper(..)   
 (api/video_codecs/video_encoder_software_fallback_wrapper.cc)  


//JNI_VideoEncoderFallback_CreateEncoder 函数  如下 
static jlong JNI_VideoEncoderFallback_CreateEncoder(...) 
  //通过 JavaToNativeVideoEncoder 和 传入的 j_fallback_encoder 创建一个软解码器  
  std::unique_ptr<VideoEncoder> fallback_encoder = JavaToNativeVideoEncoder(jni, j_fallback_encoder);  
  //通过 JavaToNativeVideoEncoder 和 传入的 j_primary_encoder 创建一个硬解码器  
  //会调用到 DefaultVideoEncoderFactory.java 中 createEncoder
  std::unique_ptr<VideoEncoder> primary_encoder = JavaToNativeVideoEncoder(jni, j_primary_encoder);  
  //将软编码器和硬编码器传入 CreateVideoEncoderSoftwareFallbackWrapper
  VideoEncoder* nativeWrapper =  CreateVideoEncoderSoftwareFallbackWrapper(std::move(fallback_encoder),std::move(primary_encoder)) .release();
  return jlongFromPointer(nativeWrapper);


// 函数 VideoEncoderFactoryWrapper::CreateVideoEncoder 如下  
std::unique_ptr<VideoEncoder> VideoEncoderFactoryWrapper::CreateVideoEncoder(
    const SdpVideoFormat& format) 
  JNIEnv* jni = AttachCurrentThreadIfNeeded();
  ScopedJavaLocalRef<jobject> j_codec_info = SdpVideoFormatToVideoCodecInfo(jni, format);
  ScopedJavaLocalRef<jobject> encoder = Java_VideoEncoderFactory_createEncoder(jni, encoder_factory_, j_codec_info);
  if (!encoder.obj()) return nullptr;
  return JavaToNativeVideoEncoder(jni, encoder);



//在 VideoEncoderFactoryWrapper::CreateVideoEncoder 中可以看到 以上 encode 接着传入 JavaToNativeVideoEncoder  
std::unique_ptr<VideoEncoder> JavaToNativeVideoEncoder(..)  
Java_VideoEncoder_createNativeVideoEncoder(..) (out/release-build/arm64-v8a/gen/sdk/android/generated_video_jni/VideoEncoder_jni.h) 
createNativeVideoEncoder()  (sdk/android/api/org/webrtc/VideoEncoder.java)
//这里返回到了java层，而 VideoEncoder 只是一个接口，
//通过 DefaultVideoEncoderFactory.java 中 createEncoder 可以看到这里用的是  VideoEncoderFallback.java 
Java_org_webrtc_VideoEncoderFallback_nativeCreateEncoder (out/release-build/arm64-v8a/gen/sdk/android/generated_video_jni/VideoEncoderFallback_jni.h)  
JNI_VideoEncoderFallback_CreateEncoder(...)    (sdk/android/src/jni/video_encoder_fallback.cc)

相关类的关系图如下

另：在 internal_encoder_factory.cc 中我们可以看到有 V8 V9 H264 AV1 Encoder 的创建，如下:

std::unique_ptr<VideoEncoder> InternalEncoderFactory::CreateVideoEncoder(const SdpVideoFormat& format) 
  if (absl::EqualsIgnoreCase(format.name, cricket::kVp8CodecName))
    return VP8Encoder::Create();
  if (absl::EqualsIgnoreCase(format.name, cricket::kVp9CodecName))
    return VP9Encoder::Create(cricket::VideoCodec(format));
  if (absl::EqualsIgnoreCase(format.name, cricket::kH264CodecName))
    return H264Encoder::Create(cricket::VideoCodec(format));
  if (kIsLibaomAv1EncoderSupported &&absl::EqualsIgnoreCase(format.name, cricket::kAv1CodecName))
    return CreateLibaomAv1Encoder();
  return nullptr;

---

mediasoup H264Encoder 初始化

视频帧分发到

VideoStreamEncoder::OnFrame (webrtc/src/video/video_stream_encoder.cc)  
ReconfigureEncoder()   
--> encoder_->InitEncode(...)  
--> EncoderSimulcastProxy::InitEncode(...)  (webrtc/src/media/engine/encoder_simulcast_proxy.cc)   
--> H264EncoderImpl::InitEncode(...) (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl.cc)  
其中还会调用 `H264EncoderImpl::SetRates`、`H264EncoderImpl::CreateEncoderParams` 等  

- H264Encoder 编码  
视频帧分发到 VideoStreamEncoder::OnFrame (webrtc/src/video/video_stream_encoder.cc)  
-->  MaybeEncodeVideoFrame    
-->  VideoStreamEncoder::EncodeVideoFrame  
-->  encoder_->Encode(...)  
-->  H264EncoderImpl::Encode (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl.cc)  
-->  encoded_image_callback_->OnEncodedImage 编码完成回调  

---

webrtc H264Encoder 初始化

VideoStreamEncoder::OnFrame (webrtc/src/video/video_stream_encoder.cc)  
VideoStreamEncoder::MaybeEncodeVideoFrame 
VideoStreamEncoder::ReconfigureEncoder()
VideoEncoderSoftwareFallbackWrapper::InitEncode  (api/video_codecs/video_encoder_software_fallback_wrapper.cc)   
VideoEncoderWrapper::InitEncode  (sdk/android/src/jni/video_encoder_wrapper.cc)    
VideoEncoderWrapper::InitEncodeInternal 
Java_VideoEncoderWrapper_createEncoderCallback  (out/release-build/arm64-v8a/gen/sdk/android/generated_video_jni/VideoEncoderWrapper_jni.h)
//最终使用 JAVA 层 HardwareVideoEncoder
public VideoCodecStatus initEncode(Settings settings, Callback callback)  (sdk/android/src/java/org/webrtc/HardwareVideoEncoder.java)

---

webrtc H264Decoder初始化流程

VideoReceiver2::Decode (modules/video_coding/video_receiver2.cc)
–>
VCMDecoderDataBase::GetDecoder (modules/video_coding/decoder_database.cc)
–>
H264DecoderImpl::InitDecode (modules/video_coding/codecs/h264/h264_decoder_impl.cc)
–>
avcodec_find_decoder (third_party/ffmpeg/libavcodec/allcodecs.c)
其中 av_codec_iterate 会用到 codec_list(在 libavcodec/codec_list.c)
也就是为啥 开启h264软编解码 需要修改此处

---

openh264 提供编解码相关函数

WelsCreateDecoder;
WelsCreateSVCEncoder;
WelsDestroyDecoder;
WelsDestroySVCEncoder;
WelsGetCodecVersion;
WelsGetCodecVersionEx;

使用 openh264 编解码示例
https://blog.csdn.net/NB_vol_1/article/details/103376649

---

webrtc 视频 H264 硬编码

安卓设备由于碎片化，早期的版本并不支持硬编码，又存在不同的芯片厂商如高通、MTK、海思、三星等
最终并不是所有安卓设备都支持硬编解码

• 修改 MediaCodecUtils.java 中 SOFTWARE_IMPLEMENTATION_PREFIXES
  建议把 "OMX.SEC." 去掉
  因为在 HardwareVideoDecoderFactory.java 和 PlatformSoftwareVideoDecoderFactory 中，
  MediaCodecUtils.SOFTWARE_IMPLEMENTATION_PREFIXES 包含芯片厂家被加不支持硬编码黑名单了。。。

• 支持的 H264 的芯片代码前缀如下，参考自 一朵桃花压海棠 博文

private static final String[] supportedH264HwCodecPrefixes = 
    "OMX.qcom.", "OMX.Intel.", "OMX.Exynos."
    ,"OMX.Nvidia.H264."     /*Nexus 7(2012), Nexus 9, Tegra 3, Tegra K1*/
    ,"OMX.ittiam.video."    /*Xiaomi Mi 1s*/
    ,"OMX.SEC.avc."         /*Exynos 3110, Nexus S*/
    ,"OMX.IMG.MSVDX."       /*Huawei Honor 6, Kirin 920*/
    ,"OMX.k3.video."        /*Huawei Honor 3C, Kirin 910*/
    ,"OMX.hisi."            /*Huawei Premium Phones, Kirin 950*/
    ,"OMX.TI.DUCATI1."      /*Galaxy Nexus, Ti OMAP4460*/
    ,"OMX.MTK.VIDEO."       /*no sense*/
    ,"OMX.LG.decoder."      /*no sense*/
    ,"OMX.rk.video_decoder."/*Youku TVBox. our service doesn't need this */
    ,"OMX.amlogic.avc"      /*MiBox1, 1s, 2. our service doesn't need this */
;

• 修改 HardwareVideoEncoderFactory.java 和 HardwareVideoDecoderFactory 相关代码以支持更多芯片
  如需暴力修改可以参考 https://www.pianshen.com/article/63171561802/

---

其它相关文档

• WebRTC on Android: how to enable hardware encoding on multiple devices
  https://medium.com/bumble-tech/webrtc-on-android-how-to-enable-hardware-encoding-on-multiple-devices-5bd819c0ce5

• 安卓webrtc在ubuntu 2004下编译使用
  https://blog.csdn.net/CSqingchen/article/details/120016697

• Android 断点调试 webrtc、 medieasoup
  https://blog.csdn.net/CSqingchen/article/details/120156900

• 安卓增加 mediasoup webrtc 日志输出
  https://blog.csdn.net/CSqingchen/article/details/120156669

• 安卓 Mediasoup V3 基于webrtc 分支m84 的编译
  https://blog.csdn.net/CSqingchen/article/details/120163087

• 安卓 webrtc 开启h264 软编解码
  https://blog.csdn.net/CSqingchen/article/details/120199702

• 安卓mediasoup输出H264流(支持H264编码)
  https://blog.csdn.net/CSqingchen/article/details/120218832

• 安卓mediasoup webrtc h264 软编解码相关源码分析
  https://blog.csdn.net/CSqingchen/article/details/120218923