在previewFrame不会被调用为显示在SurfaceView每一帧 [英] onPreviewFrame not being called for every frame that is displayed on SurfaceView

问题描述

我的 SurfaceView 工具相机previewCallback ＆安培的子类; SurfaceHolder.Callback 。

My subclass of SurfaceView implements Camera.PreviewCallback & SurfaceHolder.Callback.

private SurfaceHolder mHolder;
private Camera mCamera;

private final FPSCounter fpscounter = new FPSCounter();

public MySurfaceView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mHolder = getHolder();
    mHolder.addCallback(this);
}

@Override
public void onPreviewFrame(byte[] data, Camera camera) {
    fpscounter.logFrame();
    Log.d("fps", String.valueOf(fpscounter.getLastFrameCount()));
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    synchronized (this) {
        mCamera.stopPreview();

        Camera.Parameters parameters = mCamera.getParameters();
        parameters.setRecordingHint(true);
        parameters.setPreviewFormat(ImageFormat.NV21);

        mCamera.setParameters(parameters);

        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.setPreviewCallback(this);
            mCamera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
    synchronized (this) {
        setWillNotDraw(false);
        mCamera = Camera.open();
    }
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    synchronized (this) {
        try {
            if (mCamera != null) {
                mCamera.stopPreview();
                mCamera.release();
            }
        } catch (Exception e) {
            Log.e("cam error", e.getMessage());
        }
    }
}

和 FPSCounter 类

private long startTime; 
private int frames, lastFrameCount;

public void logFrame() {
    frames++;
    if (System.nanoTime() - startTime >= 1000000000) {
        lastFrameCount = frames;
        frames = 0;
        startTime = System.nanoTime();
    }
}

public int getLastFrameCount() {
    return lastFrameCount;
}

即使相机preVIEW极为流畅，上previewFrame（）只调用了第二个5次左右。为什么是不是被要求对每一帧？

Even though the camera preview is extremely smooth, the onPreviewFrame() method is only called about 5 times a second. Why isn't it being called for every frame?

推荐答案

您可能想通了已经：Camera.set previewCallback（）把太多pressure的垃圾收集器。您可以使用Camera.set previewCallbackWithBuffer（）代替。

You probably figured it out already: Camera.setPreviewCallback() puts too much pressure on Garbage Collector. You can use Camera.setPreviewCallbackWithBuffer() instead.

二，如果previewFrame（）到达主（UI）线程，那么它的竞争对手的单CPU时间像触摸，布局，甚至渲染UI事件。为了保持在previewFrame（）在一个单独的线程，你应该打开（）在二级弯针线相机，例如见<一href=\"http://stackoverflow.com/a/19154438/192373\">http://stackoverflow.com/a/19154438/192373.

Second, if onPreviewFrame() arrives on the main (UI) thread, then it competes for single CPU time with UI events like touch, layout, or even rendering. To keep onPreviewFrame() on a separate thread, you should open() the camera on a secondary Looper thread, see e.g. http://stackoverflow.com/a/19154438/192373.

第三，即使在这种情况下，preVIEW回调被序列。如果 fpscounter.logFrame（）和日志（）。ð拍X毫秒，那么FPS将不会超过1000 / [X]。

Third, even in this case, the preview callbacks are serialized. If fpscounter.logFrame() and Log().d take X milliseconds, then the FPS will not exceed 1000/X.

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