捕获Camera2预览帧返回空缓冲区

Question

我一直在开发一个简单的Android应用程序，旨在将流式相机帧从Android Camera2 API管道传递到我的算法中。我已经制作了几个应用程序，都是使用Android Camera1 API忠实地完成此操作的，但即使在检查（Google文档、论坛）以确认正确编码后，我仍无法从onImageAvailable()中的ImageReader中捕获任何真实数据。请注意以下相关代码：

1. Setting up the ImageReaders:

   private void setUpCameraOutputs(int width, int height) {
   
   [....code....]
   
   mImageReader = ImageReader.newInstance(smallestJPEG.getWidth(), 
                                          smallestJPEG.getHeight(),
                                          ImageFormat.JPEG, /*maxImages*/2);
   // mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, null);
   mPreviewImageReader = ImageReader.newInstance(smallest.getWidth(), 
                                                 smallest.getHeight(), 
                                                 ImageFormat.YUV_420_888, 2);
   mPreviewImageReader.setOnImageAvailableListener(mOnPreviewImageAvailableListener,
                                                   mBackgroundHandler);
   
   [....code....]
   
   }
   

2. Setting up the CaptureSession:

   private void createCameraPreviewSession() {
   try {
       //Create Texture from Screen's TextureView
       SurfaceTexture texture = mTextureView.getSurfaceTexture();
   
       assert texture != null;
   
       //Configure Default Buffer Size
       texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
   
       //Create Output Surface from Texture
       Surface surface = new Surface(texture);
   
       // Set up a CaptureRequest.Builder with the output Surface.
       mPreviewRequestBuilder
               = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
   
       //Add Output Display surface
       mPreviewRequestBuilder.addTarget(surface);
   
       //Add Preview frame-grabbing surface 
       mPreviewRequestBuilder.addTarget(mPreviewImageReader.getSurface());
   
       mCameraDevice.createCaptureSession(Arrays.asList(surface, mPreviewImageReader.getSurface()),
               new CameraCaptureSession.StateCallback() {
   
                   @Override
                   public void onConfigured(CameraCaptureSession cameraCaptureSession) {
                       // The camera is already closed
                       if (null == mCameraDevice) {
                           return;
                       }
   
                       // When the session is ready, we start displaying the preview.
                       mCaptureSession = cameraCaptureSession;
                       try {
                           // Auto focus should be continuous for camera preview. [...code...]
                           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) {
                           [...code...]
                       }
                   }
   
                   @Override
                   public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                       [...code...]
                   }
               }, null
       );
   } catch (CameraAccessException e) {
       [...code...]
   }
   }
   

3. Setting up the OnImageAvailableListener:

   private ImageReader mPreviewImageReader;
   private final ImageReader.OnImageAvailableListener mOnPreviewImageAvailableListener
   = new ImageReader.OnImageAvailableListener() {
   
   @Override
   public void onImageAvailable(ImageReader reader) {
   
       //Acquire Image, ByteBuffer, then byte array
       Image image = reader.acquireLatestImage();
       ByteBuffer buffer = image.getPlanes()[0].getBuffer();
       byte[] bytes = new byte[buffer.remaining()];
   
       //Check bytes array for anydata
       int cnt = 0;
       for (int i = 0; i < bytes.length; i++){
           if (bytes[i] != 0)cnt++;
       }
       Log.i(TAG, "cnt = " + cnt);
       image.close();
   
       //At this point, byte[] bytes is empty (all zero)
       [...code...]
   }
   
   };
   

在代码片段＃3中，无论ImageReader格式如何，我的字节缓冲区始终返回空（全零）。是否有人遇到过这个问题？我有没有漏掉任何代码？

- shandroid

---

我也遇到了同样的问题。你解决了吗？ - SasukeIsCool

我相信在我的onImageAvailable示例中缺少了"buffer.get(bytes)"（将其作为实际代码的第四行）。 - shandroid

你是如何处理“无法在尚未调用Looper.prepare()的线程中创建handler”的问题的？ - Bjqn

Answer 1

在byte[] bytes = new byte[buffer.remaining()];之后加上buffer.get(bytes);。

- Elena Naumova

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许多在线样本实际上都存在这个错误，如果你不仔细看，很容易就会错过它。 - Jay Snayder

Answer 2

you miss some code check this,

 ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();
        byte[] bytes = new byte[buffer.remaining()];
        buffer.get(bytes);
        FileOutputStream output = null;
        try {
            output = new FileOutputStream(mFile);
            output.write(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            mImage.close();
            if (null != output) {
                try {
                    output.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

- Mayur Dabhi