WebRTC之摄像头预览

本文主要是介绍WebRTC之摄像头预览，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

在前面《WebRTC之服务器搭建》 我们已经搭建好了WebRTC所需的服务器环境，主要是三个服务器：
房间服务器、信令服务器以及TURN穿透服务器。

后续我们将学习如何使用WebRTC一步一步实现音视频通话。今天我们将学习如何使用WebRTC预览摄像头数据。

这里透个底，后面的学习过程中大部分的实践都是基于WebRTC的官方封装库，因此绝大部分的代码都是Java或者Kotlin，暂时不会涉及到JNI的相关代码，所以门槛还是非常低的。

Good good study，day day up. So easy…

引入依赖库

首先我们在Android Studio工程中引入WebRTC的依赖库:

 implementation 'org.webrtc:google-webrtc:1.0.+'

动态权限

首先肯定是需要CAMERA权限的，如果需要音频数据则还需要RECORD_AUDIO权限。

对于动态权限相信有Android开发基础的童鞋们都不陌生了，gitHub上也有很多相关的开源库，笔者在这里就不多做介绍了。

预览摄像头

WebRTC作为一个点对点通信完整的解决方案，对于摄像头数据的获取及预览都已经做好了完整封装，开发者直接调用相关的API即可，
并不需要开发者编写OpenGL纹理渲染等相关的逻辑代码。

如果童鞋们对如何使用OpenGL渲染摄像头数据感兴趣的话可以参考笔者之前的文章：《使用OpenGL预览CameraX摄像头数据》

使用WebRTC预览摄像头数据主要有以下几个步骤：

1、创建EglBase及SurfaceViewRenderer

其中EglBase一个重要的功能就是提供EGL的渲染上下文及EGL的版本兼容。

SurfaceViewRenderer则是一个继承于SurfaceView的渲染View，提供了OpenGL渲染图像数据的功能。

// 创建EglBase
rootEglBase = EglBase.create()
camera_preview.init(rootEglBase?.eglBaseContext, null)
//硬件加速
camera_preview.setEnableHardwareScaler(true)
camera_preview.setScalingType(RendererCommon.ScalingType.SCALE_ASPECT_FILL)

2、创建VideoCapturer

VideoCapturer主要作用则是提供摄像头数据，比如控制分辨率以及帧率等。

通过CameraEnumerator接口兼容Camera1和Camera2：

   // 创建VideoCapturerprivate fun createVideoCapture(): VideoCapturer? {return if (Camera2Enumerator.isSupported(this)) {createCameraCapture(Camera2Enumerator(this))} else {createCameraCapture(Camera1Enumerator(true))}}//  真正创建VideoCapturer的实现private fun createCameraCapture(enumerator: CameraEnumerator): VideoCapturer? {val deviceNames = enumerator.deviceNames// First, try to find front facing camerafor (deviceName in deviceNames) {if (enumerator.isFrontFacing(deviceName)) {val videoCapture: VideoCapturer? = enumerator.createCapturer(deviceName, null)if (videoCapture != null) {return videoCapture}}}for (deviceName in deviceNames) {if (!enumerator.isFrontFacing(deviceName)) {val videoCapture: VideoCapturer? = enumerator.createCapturer(deviceName, null)if (videoCapture != null) {return videoCapture}}}return null}

VideoCapturer创建完成之后需要使用SurfaceTextureHelper进行初始化，否则调用预览的时候会抛出未初始化的异常：

  // 初始化mSurfaceTextureHelper =SurfaceTextureHelper.create("CaptureThread", rootEglBase?.eglBaseContext)// 创建VideoSourceval videoSource = mPeerConnectionFactory!!.createVideoSource(false)mVideoCapture?.initialize(mSurfaceTextureHelper,applicationContext,videoSource.capturerObserver)/*** 创建PeerConnectionFactory*/private fun createPeerConnectionFactory(context: Context?): PeerConnectionFactory? {val encoderFactory: VideoEncoderFactoryval decoderFactory: VideoDecoderFactoryencoderFactory = DefaultVideoEncoderFactory(rootEglBase?.eglBaseContext,false /* enableIntelVp8Encoder */,true)decoderFactory = DefaultVideoDecoderFactory(rootEglBase?.eglBaseContext)PeerConnectionFactory.initialize(PeerConnectionFactory.InitializationOptions.builder(context).setEnableInternalTracer(true).createInitializationOptions())val builder = PeerConnectionFactory.builder().setVideoEncoderFactory(encoderFactory).setVideoDecoderFactory(decoderFactory)builder.setOptions(null)return builder.createPeerConnectionFactory()}

3、创建VideoTrack

VideoTrack是视频轨道，类似的还有AudioTrack音频轨道，它的作用将VideoCapturer获取到的视频数据结合VideoSource输出到SurfaceViewRenderer渲染显示。

val VIDEO_TRACK_ID = "1" //"ARDAMSv0"
// 创建VideoTrackmVideoTrack = mPeerConnectionFactory!!.createVideoTrack(VIDEO_TRACK_ID,videoSource)mVideoTrack?.setEnabled(true)// 绑定渲染ViewmVideoTrack?.addSink(camera_preview)

使用VideoCapturer开启渲染

在Activity的相关生命周期中开启预览即可：

   override fun onResume() {super.onResume()// 开启摄像头预览mVideoCapture?.startCapture(VIDEO_RESOLUTION_WIDTH,VIDEO_RESOLUTION_HEIGHT,VIDEO_FPS)}

完整代码

CapturePreviewActivity.kt:

package com.fly.webrtcandroidimport android.content.Context
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import org.webrtc.*/*** 摄像头预览*/
class CapturePreviewActivity : AppCompatActivity() {val VIDEO_TRACK_ID = "1" //"ARDAMSv0"private val VIDEO_RESOLUTION_WIDTH = 1280private val VIDEO_RESOLUTION_HEIGHT = 720private val VIDEO_FPS = 30//    绘制全局的上下文private var rootEglBase: EglBase? = nullprivate var mVideoTrack: VideoTrack? = nullprivate var mPeerConnectionFactory: PeerConnectionFactory? = null//纹理渲染private var mSurfaceTextureHelper: SurfaceTextureHelper? = nullprivate var mVideoCapture: VideoCapturer? = nullprivate val camera_preview by lazy {findViewById<SurfaceViewRenderer>(R.id.camera_preview)}override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_capture_preview)rootEglBase = EglBase.create()camera_preview.init(rootEglBase?.eglBaseContext, null)//悬浮顶端camera_preview.setZOrderMediaOverlay(true)//硬件加速camera_preview.setEnableHardwareScaler(true)camera_preview.setScalingType(RendererCommon.ScalingType.SCALE_ASPECT_FILL)mPeerConnectionFactory = createPeerConnectionFactory(this)mVideoCapture = createVideoCapture()// 初始化mSurfaceTextureHelper =SurfaceTextureHelper.create("CaptureThread", rootEglBase?.eglBaseContext)// 创建VideoSourceval videoSource = mPeerConnectionFactory!!.createVideoSource(false)mVideoCapture?.initialize(mSurfaceTextureHelper,applicationContext,videoSource.capturerObserver)mVideoTrack = mPeerConnectionFactory!!.createVideoTrack(VIDEO_TRACK_ID,videoSource)mVideoTrack?.setEnabled(true)mVideoTrack?.addSink(camera_preview)}/*** 创建PeerConnectionFactory*/private fun createPeerConnectionFactory(context: Context?): PeerConnectionFactory? {val encoderFactory: VideoEncoderFactoryval decoderFactory: VideoDecoderFactoryencoderFactory = DefaultVideoEncoderFactory(rootEglBase?.eglBaseContext,false /* enableIntelVp8Encoder */,true)decoderFactory = DefaultVideoDecoderFactory(rootEglBase?.eglBaseContext)PeerConnectionFactory.initialize(PeerConnectionFactory.InitializationOptions.builder(context).setEnableInternalTracer(true).createInitializationOptions())val builder = PeerConnectionFactory.builder().setVideoEncoderFactory(encoderFactory).setVideoDecoderFactory(decoderFactory)builder.setOptions(null)return builder.createPeerConnectionFactory()}private fun createVideoCapture(): VideoCapturer? {return if (Camera2Enumerator.isSupported(this)) {createCameraCapture(Camera2Enumerator(this))} else {createCameraCapture(Camera1Enumerator(true))}}private fun createCameraCapture(enumerator: CameraEnumerator): VideoCapturer? {val deviceNames = enumerator.deviceNames// First, try to find front facing camerafor (deviceName in deviceNames) {if (enumerator.isFrontFacing(deviceName)) {val videoCapture: VideoCapturer? = enumerator.createCapturer(deviceName, null)if (videoCapture != null) {return videoCapture}}}for (deviceName in deviceNames) {if (!enumerator.isFrontFacing(deviceName)) {val videoCapture: VideoCapturer? = enumerator.createCapturer(deviceName, null)if (videoCapture != null) {return videoCapture}}}return null}override fun onResume() {super.onResume()// 开启摄像头预览mVideoCapture?.startCapture(VIDEO_RESOLUTION_WIDTH,VIDEO_RESOLUTION_HEIGHT,VIDEO_FPS)}}

布局文件activity_capture_preview.xml:

<?xml version="1.0" encoding="utf-8"?>
<org.webrtc.SurfaceViewRenderer xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:id="@+id/camera_preview"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".CapturePreviewActivity"></org.webrtc.SurfaceViewRenderer>

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