Question

我的应用程序目前有预览屏幕，我希望它每秒捕获许多帧用于处理。目前，我的预览只是每秒存储一个图像，但是我需要更大的fps捕获率。任何帮助将不胜感激。

另一个问题（如果可以的话）是我的图像在我的SD卡上显示时会旋转90度。到目前为止，还没有互联网解决方案帮助我解决这些问题：（

谢谢：）

    public class MyCameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback{

    private SurfaceHolder mHolder;
    private Camera mCamera;

    public MyCameraSurfaceView(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int weight,
                               int height) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.
        mCamera.setDisplayOrientation(90);

        if (mHolder.getSurface() == null){
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
            // ignore: tried to stop a non-existent preview
        }

        // make any resize, rotate or reformatting changes here

        // start preview with new settings
        try {

            mCamera.setPreviewDisplay(mHolder);
            Camera.Parameters parameters = mCamera.getParameters();
            List<Camera.Size> size = parameters.getSupportedPreviewSizes();
            parameters.setPreviewSize(size.get(0).width, size.get(0).height);
            mCamera.setParameters(parameters);
            mCamera.startPreview();

        } catch (Exception e){}

        mCamera.setPreviewCallback(new Camera.PreviewCallback() {

            public void onPreviewFrame(byte[] data, Camera camera) {

                Camera.Parameters parameters = camera.getParameters();

                int format = parameters.getPreviewFormat();

                //YUV formats require more conversion
                if (format == ImageFormat.NV21 || format == ImageFormat.YUY2 || format == ImageFormat.NV16) {
                    int w = parameters.getPreviewSize().width;
                    int h = parameters.getPreviewSize().height;

                    // Get the YuV image
                    YuvImage yuv_image = new YuvImage(data, format, w, h, null);
                    // Convert YuV to Jpeg
                    Rect rect = new Rect(0, 0, w, h);
                    ByteArrayOutputStream output_stream = new ByteArrayOutputStream();

                    yuv_image.compressToJpeg(rect, 10, output_stream);
                    byte[] byt = output_stream.toByteArray();

                    FileOutputStream outStream = null;
                    try {
                        outStream = new FileOutputStream(String.format(
                                "/sdcard/bb%d.jpg", System.currentTimeMillis() / 1000));

                        outStream.write(byt);
                        outStream.close();


                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {

                    }

                }

            }
        });

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setDisplayOrientation(90);
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();


        } catch (IOException e) {
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub

    }

}

Answer 1

首先，请注意Camera.Parameters允许您使用setPreviewFrameRate设置帧速率。该值必须在getPreviewFpsRange描述的范围内。

其次，处理byte[]中的预览帧会严重限制帧速率，因为必须复制的数据量很大。如果您想将未修改的全帧YUV数据写入磁盘，那么您目前无法选择。如果您可以处理压缩工件，并且您拥有Android 4.3或更高版本，则可以将数据保存为MPEG视频并稍后再读取帧。有关代码示例，请参阅this page上的CameraToMpegTest.java示例。

将图像旋转90度或180度可以直接进行编码。如果您不想自己编写，Bitmap类可以执行此操作。

Answer 2

setPreviewCallback()是一种简单但效率较低的请求预览框架的方法。主要问题是框架可能非常繁忙地分配byte[]块来填充，垃圾收集器可能需要付出沉重的代价。首选方法是使用setPreviewCallbackWithBuffer()，但即使这样也无法保证所需的帧速率，如 How to get raw preview data from Camera object at least 15 frames per second in Android?

中所示。

我的相机预览以每秒1帧的速度捕捉

2 个答案: