Android摄像头获取队列的回调缓冲区长度

Question

How to know the current amount of callbacks in the queue?

Sometimes the count drops to 1 callback and I only get 2 frames per second.

Setup:

private void setupCallback(int bufferSize)
{
    mCamera.setPreviewCallbackWithBuffer(this);
    for (int i = 0; i <= NUM_BUFFERS; ++i)
    {
        byte[] cameraBuffer = new byte[bufferSize];
        mCamera.addCallbackBuffer(cameraBuffer);
    }
}

@Override
public void onPreviewFrame(byte[] data, Camera camera)
{
    processFrame(data);
    camera.addCallbackBuffer(data);
}

Log says:

D/Camera-JNI: Using callback buffer from queue of length 4

But sometimes with the same code it says:

D/Camera-JNI: Using callback buffer from queue of length 1

How can I know that something went wrong and resetup those buffers?

Answer 1

There's no way to do this in the Android API. You can move processFrame to another thread so that onPreviewFrame is essentially non-blocking. This way bulk of the queue will be within your process and you'll be able to keep track of it.

You should also note that onPreviewFrame is called on the same thread on which you called Camera.open() . If that thread is busy doing something, the onPreviewFrame will not be called and the corresponding buffer will drop out of the buffer pool. For this reason, I recommend that you have a dedicated thread for handling the Camera .