Android：无法从相机获得30 fps

Question

我正在使用ImageReader通过Camera2 API从手机的摄像头获取帧。 我在onConfigured回调函数中设置了RepeatingRequest并在onImageAvialable函数中记录了image.getTimestamp来计算fps。 当我查看logcat上的时间戳时，我看到只有20 fps（每秒20个时间戳）。

我的问题是：

1. 我计算fps的方法好吗？ 有没有更好的办法？
2. 如果效果很好，那为什么我却获得20 fps而不是30 fps？

以下是代码的相关部分：

public void onImageAvailable(ImageReader imageReader) {
        Image image = imageReader.acquireLatestImage();
        Log.d(TAG, "onImageAvailable: IMAGE AVAILABLE" + image.getTimestamp() );
        // If STOP CAPTURE button hasn't been pressed yet

        if ((!isStopped) && (image != null)) {

            // Get the current frame
            ByteBuffer pixelArray1 = image.getPlanes()[0].getBuffer();
            byte[] bytes = new byte[pixelArray1.remaining()];
            pixelArray1.get(bytes);

            Mat mat = new Mat(image.getHeight() + image.getHeight() / 2, image.getWidth(), CvType.CV_8UC1);
            mat.put(0, 0, bytes);
            Mat rgb = new Mat(image.getHeight(), image.getWidth(), CvType.CV_8UC4);

            // OpenCV function - convert from YUV which is the camera format into RGB which can be processed
            Imgproc.cvtColor(mat, rgb, Imgproc.COLOR_YUV420sp2BGR, 4);

            int pixelStride = image.getPlanes()[0].getPixelStride();
            int rowStride = image.getPlanes()[0].getRowStride();
            int rowPadding = rowStride - pixelStride * 640;

            final Bitmap bitmap = Bitmap.createBitmap(640 + rowPadding / pixelStride, 480, Bitmap.Config.RGB_565);
            Utils.matToBitmap(rgb, bitmap);
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    // Update screen with new frame
                    imageView.setImageBitmap(bitmap);
                }
            });
            image.close();
        }
        else {
            closeCamera();
        }
    }
};

onConfigured：

public void onConfigured(CameraCaptureSession cameraCaptureSession) {
        Log.d(TAG, "onConfigured: BUILD REQUEST AND CAPTURE");
        try {
            CaptureRequest.Builder requestBuilder = cameraCaptureSession.getDevice().createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
            requestBuilder.addTarget(imageReaderSurface);
            //cameraCaptureSession.setRepeatingRequest(requestBuilder.build(), null, handler);
            cameraCaptureSession.setRepeatingRequest(requestBuilder.build(), null, handler);
            Log.d(TAG, "onConfigured: AFTER CAPTURE");
        } catch (CameraAccessException e) {
            Log.d(TAG, "onConfigured: CANT CREATE CAPTURE REQUEST");
            e.printStackTrace();
        }
    }

并显示每秒20个时间戳的logcat：

03-24 11:41:30.919 16254-17780/com.example.noamm_000.talkwithcompviawifi 

D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176055988501
03-24 11:41:30.964 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176106451209
03-24 11:41:31.014 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176156344543
03-24 11:41:31.067 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176205880116
03-24 11:41:31.120 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176256464074
03-24 11:41:31.168 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176306533293
03-24 11:41:31.217 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176357056886
03-24 11:41:31.269 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176406944855
03-24 11:41:31.313 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176457030845
03-24 11:41:31.363 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176506663397
03-24 11:41:31.414 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176556684438
03-24 11:41:31.467 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176607584803
03-24 11:41:31.520 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176658480428
03-24 11:41:31.567 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176706916105
03-24 11:41:31.613 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176757571834
03-24 11:41:31.664 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176807395636
03-24 11:41:31.717 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176857408865
03-24 11:41:31.767 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176907807199
03-24 11:41:31.816 16254-17780/com.example.noamm_000.talkwithcompviawifi D/CAMERA_IMAGE_READY:: onImageAvailable: IMAGE AVAILABLE39176957648657

*我尝试在onImageAvialable中完成的所有工作都添加onImageAvialable ，只留下时间戳记录，但我仍然获得20 fps。

谢谢诺姆

Answer 1

您所看到的是正常的。

setRepeatingRequest的文档明确指出：“通过这种方法，摄像头设备将使用所提供的CaptureRequest中的设置以最大可能的速率连续捕获图像。” 您将获得的帧速率取决于许多因素-捕获请求设置，相机硬件，可用的cpu功率，捕获的图像等。