多线程Android摄像头帧处理 [英] Android Camera Frame processing with MultiThreading

问题描述

我使用的OpenCV，Vuforia和的tesseract（苔丝二）我的应用程序。我的系统是这样工作的：

I am using OpenCV,Vuforia and Tesseract(tess-two) for my app. My system works like this:

1. Vuforia检测目标，并将完整的帧的OpenCV（JNI）
2. OpenCV中得到帧做了一些图像处理，使之可读的的tesseract（JNI）
3. 的tesseract（苔丝二）主罚字节数组从OpenCV中，并不会在图像上的OCR处理（字节数组）

我的问题开始的第三部分。由于我的目标是做实时摄像头帧的OCR，我想使用多线程使用户界面良好，没有造成现场摄像机的视觉走缓。

My problem starts with the 3rd part. Since my aim is to do the ocr on real time camera frames, i am trying to use multi-threading to make UI smooth and not to cause live camera visual to go slow.

我决定使用AsyncTask的该是这样的：

I decided to use AsyncTask for that like this :

public void getFromNative(final byte[] imagedata, final int width,final int height,final byte [] typeData, final int typeWidth,final int typeHeight) {

        new AsyncTask<Void, Void, Void>() {

            @Override
            protected Void doInBackground(Void... params) {
                ocr(imagedata, width, height,typeData,typeWidth,typeHeight);                    
                return null;
            }

        }.execute();                
}

这让现场摄像机流比正常的，单个线程的方式平滑。但问题是，因为它开始的，因为直播相机帧那么多的AsyncTask，甚至当我打开相机远离目标，它不断在$ P $做OCR pviously创建AsycnTask并返回结果他们一个接一个。除了AsyncTask的，我想IntenService，但结果是一样的。

It makes the live camera stream smoother than normal, single thread way. But the problem is since its starting so many AsyncTask because of the live camera frames, even when i turn the camera away from the target, it keeps on doing OCR on the previously created AsycnTask and returns results for them one after another. In addition to AsyncTask, i tried IntenService, but the result was the same.

我要问，如果有一种方法可以解决这个问题，使这一过程更加高效。

I want to ask if there is a way to solve this issue and make the process more efficient.

感谢

推荐答案

我的建议，你不要试图识别每一个帧相机peview提取。我们采用了类似下面的内容在previewFrame法：

I'm suggesting, that you don't try to recognize every single frame your camera peview fetches. We used something similar to the following onPreviewFrame-method:

public final void onPreviewFrame(final byte[] data, final Camera camera) {
    this.data = data;
    now = Calendar.getInstance().getTimeInMillis();

    if (now - lastRecognitionTime > TIME_BETWEEN_RECOGNITION_STARTS_IN_MILLIS) {
        lastRecognitionTime = now;
        startRecognition(); // here you can start your async task
    }
}

这意味着识别过程只启动每隔数preVIEW帧，这取决于你如何配置TIME_BETWEEN_RECOGNITION_STARTS_IN_MILLIS。

That means the recognition process starts only every few preview frames, depending how you configure TIME_BETWEEN_RECOGNITION_STARTS_IN_MILLIS.

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