Why is the default android camera preview smoother than my own camera preview?

Question

I just setup a very basic camera preview that displays the camera full screen. I compared the smoothness of both my app and the android camera and figured that the android camera seems a lot smoother.

Why is that the case? Are there any special tricks to improve the camera preview performance?

Answer 1

I faced the same issue a time ago, and it turned out to be related with the camera resolution. Chances are that your Camera is initializing with the maximum available resolution, which may slow down performance during preview. Try and set a lower picture size with something like this.-

Camera.Parameters params = camera.getParameters();
params.setPictureSize(1280, 960);
camera.setParameters(params);

Notice that you'll need to set an available picture size. You can check available sizes with

camera.getParameters().getSupportedPictureSizes();

Hope it helps.

EDIT

It seems using a picture size with different aspect ratio than the default one, slows down performance as well. This is how I choose my pictureSize.-

First off, I get the aspect ratio of the camera default pictureSize

Camera.Parameters params = camera.getParameters();
defaultCameraRatio = (float) params.getPictureSize().width / (float) params.getPictureSize().height;

And then I get a lower pictureSize that fits the same ratio.-

private Size getPreferredPictureSize() {
    Size res = null;
    List<Size> sizes = camera.getParameters().getSupportedPictureSizes();

    for (Size s : sizes) {
        float ratio = (float) s.width / (float) s.height;
        if (ratio == defaultCameraRatio && s.height <= PHOTO_HEIGHT_THRESHOLD) {
            res = s;
    break;
        }
    }
    return res;
}

Where PHOTO_HEIGHT_THRESHOLD is the max height you want to allow.

Answer 2

This answer is a bit late, but after struggling with the same problem, I figured I'd share what I found.

Not only was I unable to match the stock camera's "smoothness", but I was also unable to match the metering of the stock camera. My live preview was much darker compared to the stock camera, especially in low light situations.

My solution was ultimately an FPS issue, as originally proposed by Robin in an early comment.

The default preview FPS on the Nexus 5 is a static 15 FPS. The stock android app detects and sets a preview FPS that uses a dynamic range (as long as that range includes 30fps). On a nexus 5, that range is 7fps -> 30fps. In low light the camera drops to a lower FPS to keep the preview bright, while in bright conditions it jumps to a smooth 30 fps.

Relevant code from the stock android photo app:

• The call to set the FPS starts on line 1560 of com.android.camera.PhotoModule (https://android.googlesource.com/platform/packages/apps/Camera2/+/android-4.4.4_r2.0.1/src/com/android/camera/PhotoModule.java).
• The utility it uses to identify the ideal FPS starts on line 833 of com.android.camera.util.CameraUtil (https://android.googlesource.com/platform/packages/apps/Camera2/+/android-4.4.4_r2.0.1/src/com/android/camera/util/CameraUtil.java)

Here's are the camera api calls to set the FPS using hard coded values (for the sake of simplicity) specific to a Nexus 5.

public void setFps(Camera camera) {
    Camera.Parameters params = camera.getParameters();
    params.setPreviewFpsRange(7000, 30000);
    camera.setParameters(params);
}