使用 Android 的 Camera2 API 进行视频广播

Question

我正在尝试制作一个通过互联网广播视频的应用程序，目前我正在使用已弃用的 Camera API，将 Camera.PreviewCallback 添加到 Camera 对象，然后发送来自 onPreviewFrame() 方法的字节数组Camera.PreviewCallback。

但现在我想测试新的 Camera2 API，我正在观看 Camera2BasicTutorial ，我认为我需要制作一个 CameraCaptureSession.CaptureCallback 对象来获取图像字节数组，就像教程说的那样：

CameraCaptureSession.CaptureCallback CaptureCallback
                = new CameraCaptureSession.CaptureCallback() {

            @Override
            public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                           @NonNull CaptureRequest request,
                                           @NonNull TotalCaptureResult result) {
                showToast("Saved: " + mFile);
                Log.d(TAG, mFile.toString());
                unlockFocus();


            }
        };

然后将其添加到CameraCaptureSession中：

mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);

问题是我不知道如何从 CaptureCallback 的 onCaptureCompleted() 中的任何参数中检索每个图像字节数组。

有什么帮助吗？

Answer 1

您说得对 - 您无法从 onCaptureCompleted() 方法中获取图像数据。该回调仅返回有关您自己簿记的曝光的元数据。实际的图像信息将发送到您在曝光的CaptureRequest 中指定的任何Surface。

Answer 2

至少我意识到如何做我想做的事，从Camera2BasicTutorial，我对Camera2BasicFragment 类做了以下更改：

1. 修改 captureStillPicture() 方法以删除我认为对我的广播需求不必要的内容，也不允许此方法停止重复模式：

   private void captureStillPicture() {
   try {
       final Activity activity = getActivity();
       if (null == activity || null == mCameraDevice) {
           return;
       }
   
       final CaptureRequest.Builder captureBuilder =
               mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
       captureBuilder.addTarget(mImageReader.getSurface());
   
       CameraCaptureSession.CaptureCallback CaptureCallback
               = new CameraCaptureSession.CaptureCallback() {
   
           @Override
           public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                          @NonNull CaptureRequest request,
                                          @NonNull TotalCaptureResult result) {
           }
       };
   
       mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
   } catch (CameraAccessException e) {
       e.printStackTrace();
   }
   }
   

2. 在createCameraPreviewSession()方法中，禁用自动全闪：

   // When the session is ready, we start displaying the preview.
                       mCaptureSession = cameraCaptureSession;
                       try {
                           // Auto focus should be continuous for camera preview.
                           mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                   CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                           // Flash is automatically enabled when necessary.
   // mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
   // CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
   
                           // Finally, we start displaying the camera preview.
                           mPreviewRequest = mPreviewRequestBuilder.build();
                           mCaptureSession.setRepeatingRequest(mPreviewRequest,
                                   mCaptureCallback, mBackgroundHandler);
                       } catch (CameraAccessException e) {
                           e.printStackTrace();
                       }
   

3. 我创建了一个布尔变量来检测当前是否正在处理图像，而不是将相机捕获的所有帧排队；和另一个布尔值来跟踪是否有通过互联网发送的帧：

   private boolean mWorking = false;
   private boolean mNetworkWorking = false;
   

4. 修改 CaptureCallback 对象以在每一帧中运行 captureStillPicture() 方法（仅当此时没有帧处理时）。

               case STATE_PREVIEW: {
   
               if (!mWorking){
                   Log.d(TAG, "capturing..");
                   mWorking = true;
   
                   mBackgroundHandler.post(new Runnable() {
                       @Override
                       public void run() {
                           captureStillPicture();
                       }
                   });
   
               } else {
                   Log.d(TAG, "thread working, doing nothing");
               }
   
   
               break;
   

5. 最后，读取帧并发送；我通过修改 OnImageAvailableListener 对象实现了这一点：

   private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
       = new ImageReader.OnImageAvailableListener() {
   
   @Override
   public void onImageAvailable(final ImageReader reader) {
   
       // Process the image.
       Image image = reader.acquireNextImage();
       ByteBuffer buffer = image.getPlanes()[0].getBuffer();
       final byte[] bytes = new byte[buffer.remaining()];
       buffer.get(bytes);
       image.close();
   
       if (!mNetworkWorking){
           Thread thread = new Thread(){
               @Override
               public void run(){
   
                   mNetworkWorking = true;
   
                   HttpResponse response = null;
                   HttpClient client = new DefaultHttpClient();
                   HttpPost post = new HttpPost(mBroadcastUrl);
                   post.setEntity(new ByteArrayEntity(bytes));
   
                   try {
                       response = client.execute(post);
                   } catch (ClientProtocolException e) {
                       if (BuildConfig.LOCAL_LOG)
                           Log.w(TAG, "ClientProtocolException: "+e.getMessage());
                   } catch (IOException e) {
                       if (BuildConfig.LOCAL_LOG)
                           Log.w(TAG, "IOException: "+e.getMessage());
                   }
   
                   mNetworkWorking = false;
   
               }
           };
   
           thread.setName("networkThread");
           thread.setPriority(Thread.MAX_PRIORITY);
           thread.start();
       }
   
       mWorking = false;
   
   }
   
   };
   

就是这样。