使用 Android 的 Camera2 API 进行视频广播

Question

我正在尝试制作一个通过互联网播放视频的应用程序，目前我正在使用已弃用的相机 API，向相机对象添加一个 Camera.PreviewCallback，然后发送字节数组来自 Camera.PreviewCallback.

的 onPreviewFrame() 方法

但现在我想测试新的 Camera2 API，我正在 Camera2BasicTutorial 观看，我认为我需要制作一个 CameraCaptureSession.CaptureCallback 对象来获取图像字节数组，就像教程说的那样：

CameraCaptureSession.CaptureCallback CaptureCallback
                = new CameraCaptureSession.CaptureCallback() {

            @Override
            public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                           @NonNull CaptureRequest request,
                                           @NonNull TotalCaptureResult result) {
                showToast("Saved: " + mFile);
                Log.d(TAG, mFile.toString());
                unlockFocus();


            }
        };

然后添加到CameraCaptureSession中：

mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);

问题是我不知道如何从 CaptureCallback 的 onCaptureCompleted() 中的任何参数中检索每个图像字节数组。

有什么帮助吗？

Answer 1

你说得对 - 你无法从 onCaptureCompleted() 方法中获取图像数据。该回调仅 returns 有关您自己簿记的曝光的元数据。实际图像信息会发送到您在曝光 CaptureRequest 中指定的任何 Surface。

Answer 2

至少我意识到如何做我想做的事情，从Camera2BasicTutorial开始，我对Camera2BasicFragment做了以下更改class：

修改 captureStillPicture() 方法以删除我认为对我的广播不需要的东西，也不允许此方法停止重复模式：

private void captureStillPicture() {
try {
    final Activity activity = getActivity();
    if (null == activity || null == mCameraDevice) {
        return;
    }

    final CaptureRequest.Builder captureBuilder =
            mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
    captureBuilder.addTarget(mImageReader.getSurface());

    CameraCaptureSession.CaptureCallback CaptureCallback
            = new CameraCaptureSession.CaptureCallback() {

        @Override
        public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                       @NonNull CaptureRequest request,
                                       @NonNull TotalCaptureResult result) {
        }
    };

    mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
} catch (CameraAccessException e) {
    e.printStackTrace();
}
}

在createCameraPreviewSession()方法中，关闭自动闪光：

// When the session is ready, we start displaying the preview.
                    mCaptureSession = cameraCaptureSession;
                    try {
                        // Auto focus should be continuous for camera preview.
                        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) {
                        e.printStackTrace();
                    }

我创建了一个布尔变量来检测当前是否有图像正在处理，而不是将相机捕获的所有帧排队；和另一个布尔值来跟踪是否有通过互联网发送的帧：
```
private boolean mWorking = false;
private boolean mNetworkWorking = false;
```

将CaptureCallback对象修改为运行每帧中的captureStillPicture()方法（仅当当前没有帧处理时）

            case STATE_PREVIEW: {

            if (!mWorking){
                Log.d(TAG, "capturing..");
                mWorking = true;

                mBackgroundHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        captureStillPicture();
                    }
                });

            } else {
                Log.d(TAG, "thread working, doing nothing");
            }


            break;

最后，读取帧并发送；我实现了这个修改 OnImageAvailableListener 对象：

private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
    = new ImageReader.OnImageAvailableListener() {

@Override
public void onImageAvailable(final ImageReader reader) {

    // Process the image.
    Image image = reader.acquireNextImage();
    ByteBuffer buffer = image.getPlanes()[0].getBuffer();
    final byte[] bytes = new byte[buffer.remaining()];
    buffer.get(bytes);
    image.close();

    if (!mNetworkWorking){
        Thread thread = new Thread(){
            @Override
            public void run(){

                mNetworkWorking = true;

                HttpResponse response = null;
                HttpClient client = new DefaultHttpClient();
                HttpPost post = new HttpPost(mBroadcastUrl);
                post.setEntity(new ByteArrayEntity(bytes));

                try {
                    response = client.execute(post);
                } catch (ClientProtocolException e) {
                    if (BuildConfig.LOCAL_LOG)
                        Log.w(TAG, "ClientProtocolException: "+e.getMessage());
                } catch (IOException e) {
                    if (BuildConfig.LOCAL_LOG)
                        Log.w(TAG, "IOException: "+e.getMessage());
                }

                mNetworkWorking = false;

            }
        };

        thread.setName("networkThread");
        thread.setPriority(Thread.MAX_PRIORITY);
        thread.start();
    }

    mWorking = false;

}

};

就这些了。

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