Android: 无法从相机获得 30 fps

Question

我正在使用 ImageReader 从 phone 使用 Camera2 API 的相机获取帧。我在 onConfigured 回调函数中设置了 RepeatingRequest，并在 onImageAvialable 函数中记录了 image.getTimestamp 以计算 fps。当我查看 logcat 上的时间戳时，我发现只有 20 fps（每秒 20 个时间戳）。

我的问题是：

我计算fps的方法好吗？有没有更好的方法？
如果它很好，那为什么我得到的是 20 fps 而不是 30？

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();
        }
    }
};

已配置：

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();
        }
    }

以及每秒显示 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

*我尝试对 onImageAvialable 中完成的所有工作发表评论，只留下时间戳记录，但我仍然得到 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 "With this method, the camera device will continually capture images using the settings in the provided CaptureRequest, at the maximum rate possible." 您将获得的帧速率取决于很多因素 - 捕获请求设置、相机硬件、可用 cpu 电源、捕获的图像等。

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