Question

我需要使用WebRTC为android将特定的裁剪（面部）视频发送到videoChannel。我能够操纵Camera1Session类WebRTC来裁剪脸部。现在我将它设置为ImageView。 listenForBytebufferFrames()

的Camera1Session.java

private void listenForBytebufferFrames() {
    this.camera.setPreviewCallbackWithBuffer(new PreviewCallback() {
        public void onPreviewFrame(byte[] data, Camera callbackCamera) {
            Camera1Session.this.checkIsOnCameraThread();
            if(callbackCamera != Camera1Session.this.camera) {
                Logging.e("Camera1Session", "Callback from a different camera. This should never happen.");
            } else if(Camera1Session.this.state != Camera1Session.SessionState.RUNNING) {
                Logging.d("Camera1Session", "Bytebuffer frame captured but camera is no longer running.");
            } else {
                mFrameProcessor.setNextFrame(data, callbackCamera);
                long captureTimeNs = TimeUnit.MILLISECONDS.toNanos(SystemClock.elapsedRealtime());
                if(!Camera1Session.this.firstFrameReported) {
                    int startTimeMs = (int)TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - Camera1Session.this.constructionTimeNs);
                    Camera1Session.camera1StartTimeMsHistogram.addSample(startTimeMs);
                    Camera1Session.this.firstFrameReported = true;
                }

                ByteBuffer byteBuffer1 = ByteBuffer.wrap(data);
                Frame outputFrame = new Frame.Builder()
                        .setImageData(byteBuffer1,
                                Camera1Session.this.captureFormat.width,
                                Camera1Session.this.captureFormat.height,
                                ImageFormat.NV21)
                        .setTimestampMillis(mFrameProcessor.mPendingTimeMillis)
                        .setId(mFrameProcessor.mPendingFrameId)
                        .setRotation(3)
                        .build();
                int w = outputFrame.getMetadata().getWidth();
                int h = outputFrame.getMetadata().getHeight();
                SparseArray<Face> detectedFaces = mDetector.detect(outputFrame);
                if (detectedFaces.size() > 0) {

                    Face face = detectedFaces.valueAt(0);
                    ByteBuffer byteBufferRaw = outputFrame.getGrayscaleImageData();
                    byte[] byteBuffer = byteBufferRaw.array();
                    YuvImage yuvimage  = new YuvImage(byteBuffer, ImageFormat.NV21, w, h, null);
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();

                    //My crop logic to get face co-ordinates

                    yuvimage.compressToJpeg(new Rect(left, top, right, bottom), 80, baos);
                    final byte[] jpegArray = baos.toByteArray();
                    Bitmap bitmap = BitmapFactory.decodeByteArray(jpegArray, 0, jpegArray.length);

                    Activity currentActivity = getActivity();
                    if (currentActivity instanceof CallActivity) {
                        ((CallActivity) currentActivity).setBitmapToImageView(bitmap); //face on ImageView is set just fine
                    }
                    Camera1Session.this.events.onByteBufferFrameCaptured(Camera1Session.this, data, Camera1Session.this.captureFormat.width, Camera1Session.this.captureFormat.height, Camera1Session.this.getFrameOrientation(), captureTimeNs);
                    Camera1Session.this.camera.addCallbackBuffer(data);
                } else {
                    Camera1Session.this.events.onByteBufferFrameCaptured(Camera1Session.this, data, Camera1Session.this.captureFormat.width, Camera1Session.this.captureFormat.height, Camera1Session.this.getFrameOrientation(), captureTimeNs);
                    Camera1Session.this.camera.addCallbackBuffer(data);
                }

            }
        }
    });
}

jpegArray是我需要通过WebRTC传输的最终byteArray，我试过这样的事情：

Camera1Session.this.events.onByteBufferFrameCaptured(Camera1Session.this, jpegArray, (int) face.getWidth(), (int) face.getHeight(), Camera1Session.this.getFrameOrientation(), captureTimeNs);
Camera1Session.this.camera.addCallbackBuffer(jpegArray);

像这样设置它会给我以下错误：

../../webrtc/sdk/android/src/jni/androidvideotracksource.cc line 82
Check failed: length >= width * height + 2 * uv_width * ((height + 1) / 2) (2630 vs. 460800)

我认为这是因为androidvideotracksource没有达到预期的byteArray长度，因为现在裁剪了帧。有人能指出我如何实现它的方向吗？这是操纵数据并输入videoTrack的正确方法/地点吗？

编辑： bitmap byteArray data不会在ImageView上为我提供相机预览，这与byteArray jpegArray不同。也许是因为他们的包装不同？

Answer 1

我们可以使用WebRTC的Datachannel来交换自定义数据，即裁剪的脸部＆＃34;图像＆＃34;在你的情况下，使用任何第三方库即OpenGL等在接收端进行相应的计算？我建议的原因是从频道收到的WebRTC视频源是实时流而不是字节数组。 WebRTC Video通过其固有的架构并不意味着另一方面裁剪视频。如果我们想裁剪或增加视频，我们必须使用任何ar库来完成这项工作。

我们始终可以利用WebRTC的数据渠道来交换自定义数据。建议不要使用视频通道，因为它的实时流不是bytearray。如果有任何问题，请恢复。

Answer 2

特别是WebRTC和视频流通常假设视频具有固定的尺寸。如果要裁剪检测到的面部，您可以选择将裁剪后的图像填充到例如黑色像素（WebRTC不使用透明度），并在接收器侧裁剪视频，或者，如果您无法控制接收器，resize裁剪区域将填充预期的width * height帧（你还应该保持预期的宽高比）。

请注意，用于裁剪原始内容的JPEG压缩/解压缩效率很低。其他一些选项可以在 Image crop and resize in Android 中找到。

Answer 3

好的，这绝对是原始byte[] data如何打包以及byte[] jpegArray包装方式的问题。正如AlexCohn所建议的那样改变包装方式和缩放方式对我有用。我在StackOverflow上找到other post的帮助以便打包它。这是它的代码：

private byte[] getNV21(int left, int top, int inputWidth, int inputHeight, Bitmap scaled) {
int [] argb = new int[inputWidth * inputHeight];
    scaled.getPixels(argb, 0, inputWidth, left, top, inputWidth, inputHeight);
    byte [] yuv = new byte[inputWidth*inputHeight*3/2];
    encodeYUV420SP(yuv, argb, inputWidth, inputHeight);
    scaled.recycle();
    return yuv;
}

private void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {
    final int frameSize = width * height;

    int yIndex = 0;
    int uvIndex = frameSize;

    int a, R, G, B, Y, U, V;
    int index = 0;
    for (int j = 0; j < height; j++) {
        for (int i = 0; i < width; i++) {

            a = (argb[index] & 0xff000000) >> 24; // a is not used obviously
            R = (argb[index] & 0xff0000) >> 16;
            G = (argb[index] & 0xff00) >> 8;
            B = (argb[index] & 0xff) >> 0;

            // well known RGB to YUV algorithm
            Y = ( (  66 * R + 129 * G +  25 * B + 128) >> 8) +  16;
            U = ( ( -38 * R -  74 * G + 112 * B + 128) >> 8) + 128;
            V = ( ( 112 * R -  94 * G -  18 * B + 128) >> 8) + 128;

            // NV21 has a plane of Y and interleaved planes of VU each sampled by a factor of 2
            //    meaning for every 4 Y pixels there are 1 V and 1 U.  Note the sampling is every other
            //    pixel AND every other scanline.
            yuv420sp[yIndex++] = (byte) ((Y < 0) ? 0 : ((Y > 255) ? 255 : Y));
            if (j % 2 == 0 && index % 2 == 0) {
                yuv420sp[uvIndex++] = (byte)((V<0) ? 0 : ((V > 255) ? 255 : V));
                yuv420sp[uvIndex++] = (byte)((U<0) ? 0 : ((U > 255) ? 255 : U));
            }

            index ++;
        }
    }
}`

我将此byte[] data传递给onByteBufferFrameCaptured和callback：

Camera1Session.this.events.onByteBufferFrameCaptured(
                            Camera1Session.this,
                            data,
                            w,
                            h,
                            Camera1Session.this.getFrameOrientation(),
                            captureTimeNs);
Camera1Session.this.camera.addCallbackBuffer(data);

在此之前，我必须缩放位图，这非常简单：

int width = bitmapToScale.getWidth();
int height = bitmapToScale.getHeight();
Matrix matrix = new Matrix();
matrix.postScale(newWidth / width, newHeight / height);
Bitmap scaledBitmap = Bitmap.createBitmap(bitmapToScale, 0, 0, bitmapToScale.getWidth(), bitmapToScale.getHeight(), matrix, true);

自定义byteArray数据到WebRTC videoTrack

3 个答案: