在增加滤镜功能之前,需要对 WebRTC 视频采集的流程有一定了解。
WebRTC 中定义了 VideoCapture 接口类,其中定义了相机的初始化,预览,停止预览销毁等操作。
实现类是 CameraCapture,并且封装了 Camera1Capture、Camera2Capture 两个子类,甚至还有屏幕共享。
WebRTC 中开始视频采集非常的简单:
val videoCapture = createVideoCapture()
videoSource = videoCapture.isScreencast.let { factory.createVideoSource(it) }
videoCapture.initialize(surfaceTextureHelper,applicationContext,videoSource?.capturerObserver)
videoCapture.startCapture(480, 640, 30)
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这里主要看一下 VideoSource 类和 capturerObserver。
VideoSource 中有以下方法
@Override
public void onFrameCaptured(VideoFrame frame) {
final VideoProcessor.FrameAdaptationParameters parameters =
nativeAndroidVideoTrackSource.adaptFrame(frame);
synchronized (videoProcessorLock) {
if (videoProcessor != null) {
videoProcessor.onFrameCaptured(frame, parameters);
return;
}
}
VideoFrame adaptedFrame = VideoProcessor.applyFrameAdaptationParameters(frame, parameters);
if (adaptedFrame != null) {
nativeAndroidVideoTrackSource.onFrameCaptured(adaptedFrame);
adaptedFrame.release();
}
}
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采集到的视频帧数据会回调给 onFrameCaptured,在这里会做一下对视频的裁切缩放处理,并通过 nativeAndroidVideoTrackSource 传递给 Native 层。
重点是 VideoProcessor 对象,据查是在 2019 年 2 月新增的。VideoSource 里面有 setVideoProcessor 方法用于设置 VideoProcessor,在上面方法中可知,如果设置了 VideoProcessor,视频帧则走 VideoProcessor 的 onFrameCaptured,否则的话直接传入 Native。
用 VideoProcessor 来实现处理发送前的视频帧非常方便,我们先来看下 VideoProcessor 类。
public interface VideoProcessor extends CapturerObserver {
public static class FrameAdaptationParameters {
...
public FrameAdaptationParameters(int cropX, int cropY, int cropWidth, int cropHeight,
int scaleWidth, int scaleHeight, long timestampNs, boolean drop) {
...
}
}
default void onFrameCaptured(VideoFrame frame, FrameAdaptationParameters parameters) {
VideoFrame adaptedFrame = applyFrameAdaptationParameters(frame, parameters);
if (adaptedFrame != null) {
onFrameCaptured(adaptedFrame);
adaptedFrame.release();
}
}
....
}
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VideoSource 中调用的 onFrameCaptured(frame, parameters) 并非 CapturerObserver 的 onFrameCaptured,也就是暂时不会传入 Native 增,它在这个方法中也做了对 ViewFrame 的裁切缩放,之后再传入底层。
所以我们可以在这里实现对视频帧的美颜滤镜处理。
class FilterProcessor : VideoProcessor{
private var videoSink:VideoSink
override fun onCapturerStarted(success: Boolean) {
}
override fun onCapturerStopped() {
}
override fun onFrameCaptured(frame: VideoFrame?) {
val newFrame = // TODO: 在这对VideoFrame进行视频滤镜美颜处理
sink.onFrame(newFrame)
}
override fun setSink(sink: VideoSink?) {
//设置视频接收器 用来渲染并将frame传入Native
videoSink = sink
}
}
val videoCapture = createVideoCapture()
videoSource = videoCapture.isScreencast.let { factory.createVideoSource(it) }
videoSource.setVideoProcessor(FilterProcessor())//设置处理器
videoCapture.initialize(surfaceTextureHelper,applicationContext,videoSource?.capturerObserver)
videoCapture.startCapture(480, 640, 30)
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美颜的话可以用 GPUImage,也可以用商用 SDK。
以上是在应用层的实现,利用 WebRTC 自带的类就行。如果是 NDK 开发,道理也是一样的。
创建一个代理类 CapturerObserverProxy 实现 CapturerObserver,并将真正的 nativeCapturerObserver 传进来,Native 会回调视频帧数据给 CapturerObserverProxy 的 onFrameCaptured,然后在 onFrameCaptured 中对视频进行美颜滤镜处理,再将处理好的 VideoFrame 用 nativeCapturerObserver 传给底层编码传输。
public class CapturerObserverProxy implements CapturerObserver {
public static final String TAG = CapturerObserverProxy.class.getSimpleName();
private CapturerObserver originalObserver;
private RTCVideoEffector videoEffector;
public CapturerObserverProxy(final SurfaceTextureHelper surfaceTextureHelper,
CapturerObserver observer,
RTCVideoEffector effector) {
this.originalObserver = observer;
this.videoEffector = effector;
final Handler handler = surfaceTextureHelper.getHandler();
ThreadUtils.invokeAtFrontUninterruptibly(handler, () ->
videoEffector.init(surfaceTextureHelper)
);
}
@Override
public void onCapturerStarted(boolean success) {
this.originalObserver.onCapturerStarted(success);
}
@Override
public void onCapturerStopped() {
this.originalObserver.onCapturerStopped();
}
@Override
public void onFrameCaptured(VideoFrame frame) {
if (this.videoEffector.needToProcessFrame()) {
VideoFrame.I420Buffer originalI420Buffer = frame.getBuffer().toI420();
VideoFrame.I420Buffer effectedI420Buffer =
this.videoEffector.processByteBufferFrame(
originalI420Buffer, frame.getRotation(), frame.getTimestampNs());
VideoFrame effectedVideoFrame = new VideoFrame(
effectedI420Buffer, frame.getRotation(), frame.getTimestampNs());
originalI420Buffer.release();
this.originalObserver.onFrameCaptured(effectedVideoFrame);
} else {
this.originalObserver.onFrameCaptured(frame);
}
}
}
videoCapturer.initialize(videoCapturerSurfaceTextureHelper, context, observerProxy);
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以上就是给 WebRTC 增加美颜功能的实现~
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