Android CameraX, increase ImageAnalysis frame rate

Question

I need to take as many frames as possible from the preview of the camera. I'm doing this to start the camera using CameraX:

private fun startCamera() {

    // Create configuration object for the viewfinder use case
    val metrics = DisplayMetrics().also { view_finder.display.getRealMetrics(it) }
    // define the screen size
    val screenSize = Size(metrics.widthPixels, metrics.heightPixels)

    val screenAspectRatio = Rational(metrics.widthPixels, metrics.heightPixels)

    val previewConfig = PreviewConfig.Builder()
        .setLensFacing(CameraX.LensFacing.BACK) // defaults to Back camera
        .setTargetAspectRatio(screenAspectRatio)
        .setTargetResolution(screenSize)
        .build()

    // Build the viewfinder use case
    val preview = Preview(previewConfig)

    // Every time the viewfinder is updated, recompute layout
    preview.setOnPreviewOutputUpdateListener {

        // To update the SurfaceTexture, we have to remove it and re-add it
        val parent = view_finder.parent as ViewGroup
        parent.removeView(view_finder)
        parent.addView(view_finder, 0)

        view_finder.surfaceTexture = it.surfaceTexture
        updateTransform()
    }
    val analyzerConfig = ImageAnalysisConfig.Builder().apply {
        // Use a worker thread for image analysis to prevent glitches
        val analyzerThread = HandlerThread("AnalysisThread").apply {
            start()
        }
        setLensFacing(CameraX.LensFacing.BACK) // defaults to Back camera
        setTargetAspectRatio(screenAspectRatio)
        setMaxResolution(Size(600, 320))
        setCallbackHandler(Handler(analyzerThread.looper))
        setImageReaderMode(ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE)
    }.build()

    val analyzerUseCase = ImageAnalysis(analyzerConfig).apply {
        analyzer = context?.let { FrameCapturer(it) }
    }

    //====================== Image Analysis Config code End==========================
    CameraX.bindToLifecycle(this, preview, analyzerUseCase)
}

My FrameCapturer class is:

class FrameCapturer(context: Context): ImageAnalysis.Analyzer {

private var mListener = context as FrameCapturerListener

override fun analyze(image: ImageProxy?, rotationDegrees: Int) {

    val buffer = image?.planes?.get(0)?.buffer
    // Extract image data from callback object
    val data = buffer?.toByteArray()
    // Convert the data into an array of pixel values
    //val pixels = data?.map { it.toInt() and 0xFF }
    mListener.updateFps()

}
private fun ByteBuffer.toByteArray(): ByteArray {
    rewind()    // Rewind the buffer to zero
    val data = ByteArray(remaining())
    get(data)   // Copy the buffer into a byte array
    return data // Return the byte array
}

interface FrameCapturerListener {
    fun updateFps()
}

And my updateFps function is:

fun updateFps() {
    fps += 1
    if (!isCountDownStarted) {
        var timer = object : CountDownTimer(1000, 1000) {
            override fun onTick(millisUntilFinished: Long) {

            }

            override fun onFinish() {
                Log.d("CameraFragment", fps.toString())
                fps = 0
                isCountDownStarted = false
            }
        }.start()
        isCountDownStarted = true
    }
}

I'm around 16-22 fps, even if I don't convert the image to an array of byte in the FrameCapturer class. So, it seems like the Analyzer take only 20 image per second. Is there a way to increase the fps? I need to take at least 40-60 image per second, because I need to do post-processing with machine learning for each frame, so they will probably drop to 20-30 after ML analysis.

EDIT: I discover that with the Pixel 2xl I got 60fps without any drop..with my device (Xiaomi Redmi Note 5 Pro) I got only 25 fps...Can I optimize the code in any way to increase FPS?