源码分析"/>
安卓mediasoup webrtc h264 编解码相关源码分析
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
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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/?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
- 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)
--> CreatePeerConnectionFactoryForJava(...) (webrtc/src/sdk/android/src/jni/pc/peer_connection_factory) 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));
}
- 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)
--> CreateMediaEngine (webrtc/src/media/engine/webrtc_media_engine)
--> WebRtcVideoEngine::WebRtcVideoEngine (webrtc/src/media/engine/webrtc_media_engine)
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)
--> PeerConnection::DoSetRemoteDescription(...)
--> PeerConnection::ApplyRemoteDescription(...)
--> PeerConnection::UpdateSessionState(...)
--> PeerConnection::PushdownMediaDescription(...)
--> BaseChannel::SetRemoteContent(...) (webrtc/src/pc/channel)
--> VoiceChannel::SetRemoteContent_w(...)
--> WebRtcVideoChannel::SetSendParameters (webrtc/src/media/engine/webrtc_video_engine)
--> WebRtcVideoChannel::ApplyChangedParams(...)
--> WebRtcVideoChannel::WebRtcVideoSendStream::SetSendParameters(...)
--> WebRtcVideoChannel::WebRtcVideoSendStream::SetCodec(..)
--> WebRtcVideoChannel::WebRtcVideoSendStream::RecreateWebRtcStream(...)
--> webrtc::VideoSendStream* Call::CreateVideoSendStream(,) (webrtc/src/call/call)
--> webrtc::VideoSendStream* Call::CreateVideoSendStream(,,)
--> VideoSendStream::VideoSendStream(..) (webrtc/src/video/video_send_stream)
--> std::unique_ptr<VideoStreamEncoderInterface> CreateVideoStreamEncoder(..) (webrtc/src/api/video/video_stream_encoder_create)
--> VideoStreamEncoder::VideoStreamEncoder(...) (webrtc/src/video/video_stream_encoder)
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)
--> PeerConnection::DoSetLocalDescription
--> PeerConnection::ApplyLocalDescription
--> PeerConnection::UpdateSessionState
--> PeerConnection::PushdownMediaDescription() (pc/peer_connection)
--> BaseChannel::SetLocalContent() (pc/channel)
--> VideoChannel::SetLocalContent_w(...)
--> BaseChannel::UpdateLocalStreams_w(..)
--> WebRtcVideoChannel::AddSendStream(..) (media/engine/webrtc_video_engine)
--> WebRtcVideoChannel::WebRtcVideoSendStream::WebRtcVideoSendStream(..)
--> WebRtcVideoChannel::WebRtcVideoSendStream::SetCodec(..)
--> WebRtcVideoChannel::WebRtcVideoSendStream::RecreateWebRtcStream()
--> webrtc::VideoSendStream* Call::CreateVideoSendStream(..) (call/call)
--> VideoSendStream::VideoSendStream(..) (video/video_send_stream)
--> std::unique_ptr<VideoStreamEncoderInterface> CreateVideoStreamEncoder(..) (api/video/video_stream_encoder_create)
--> VideoStreamEncoder::VideoStreamEncoder() (video/video_stream_encoder)
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)
--> VideoStreamEncoder::ReconfigureEncoder()
--> encoder_ = settings_.encoder_factory->CreateVideoEncoder(encoder_config_.video_format) (webrtc/src/video/video_stream_encoder)
//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)
--> EncoderSimulcastProxy::EncoderSimulcastProxy (webrtc\src\media\engine\encoder_simulcast_proxy)
--> InternalEncoderFactory::CreateVideoEncoder (webrtc/src/media/engine/internal_encoder_factory)
--> H264Encoder::Create() (webrtc/src/modules/video_coding/codecs/h264/h264)
--> H264EncoderImpl::H264EncoderImpl (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl)
- 如下是 webrtc AppRTCDemo 中 调用栈堆
--> VideoEncoderFactoryWrapper::CreateVideoEncoder (sdk/android/src/jni/video_encoder_factory_wrapper)
--> 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)
--> CreateVideoEncoderSoftwareFallbackWrapper() (api/video_codecs/video_encoder_software_fallback_wrapper)
//VideoEncoderSoftwareFallbackWrapper 是最终的 Encode
--> VideoEncoderSoftwareFallbackWrapper::VideoEncoderSoftwareFallbackWrapper(..) (api/video_codecs/video_encoder_software_fallback_wrapper) //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 createEncoderstd::unique_ptr<VideoEncoder> primary_encoder = JavaToNativeVideoEncoder(jni, j_primary_encoder); //将软编码器和硬编码器传入 CreateVideoEncoderSoftwareFallbackWrapperVideoEncoder* 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)
相关类的关系图如下
另：在 internal_encoder_factory 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)
ReconfigureEncoder()
--> encoder_->InitEncode(...)
--> EncoderSimulcastProxy::InitEncode(...) (webrtc/src/media/engine/encoder_simulcast_proxy)
--> H264EncoderImpl::InitEncode(...) (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl)
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)
--> MaybeEncodeVideoFrame
--> VideoStreamEncoder::EncodeVideoFrame
--> encoder_->Encode(...)
--> H264EncoderImpl::Encode (webrtc/src/modules/video_coding/codecs/h264/h264_encoder_impl)
--> encoded_image_callback_->OnEncodedImage 编码完成回调
webrtc H264Encoder 初始化
VideoStreamEncoder::OnFrame (webrtc/src/video/video_stream_encoder)
VideoStreamEncoder::MaybeEncodeVideoFrame
VideoStreamEncoder::ReconfigureEncoder()
VideoEncoderSoftwareFallbackWrapper::InitEncode (api/video_codecs/video_encoder_software_fallback_wrapper)
VideoEncoderWrapper::InitEncode (sdk/android/src/jni/video_encoder_wrapper)
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)
–>
VCMDecoderDataBase::GetDecoder (modules/video_coding/decoder_database)
–>
H264DecoderImpl::InitDecode (modules/video_coding/codecs/h264/h264_decoder_impl)
–>
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
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 /
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