如何以高 FPS 记录我的电脑屏幕？

Question

I'm trying to add a high FPS screen recorder to my application. I use Python 3.7 on Windows. The modules and methods I've tried are mss (python-mss) and d3dshot , but I'm still only achieving 15-19 FPS for a long video (more than 20 seconds). The resolution I'm recording at is 1920 x 1080.

What is the best way to optimize screen recording? I've tried to use the multiprocessing library, but it seems like it's still not fast enough. I'm not sure I'm using it in the optimal way, what are some ways I could use it to improve processing performance?

Using OBS Studio, I'm able to get 30 FPS, no matter how long the video is. My objective is to achieve the same results with my own code.

Here is what I've written so far:

from multiprocessing import Process, Queue
from time import sleep, time

import cv2
import d3dshot
import numpy as np


def grab(queue):


    d = d3dshot.create(capture_output="numpy", frame_buffer_size=500)

    d.capture()
    sleep(0.1)
    c=0
    
    begin = time()

    while time() - begin < 30:
        starter = time()

        frame = d.get_latest_frame()

        queue.put(frame)
        c+=1
        ender = time()

        sleep(max(0, 1/60 - (ender -starter)))

    # Tell the other worker to stop
    queue.put(None)

    final=time()
    
    print(c/(final-begin))

    d.stop()


def save(queue):
    SCREEN_SIZE = 1920, 1080
    
    # Define the codec and create VideoWriter object
    fourcc = cv2.VideoWriter_fourcc(*'DIVX') # In Windows: DIVX 
    out = cv2.VideoWriter(r"output.avi",fourcc, 30.0, (SCREEN_SIZE))
    # type: (Queue) -> None

    last_img = None
    while "there are screenshots":

        img = queue.get()
        if img is None:
            break
        if img is last_img:
            continue
        
        out.write(cv2.cvtColor(img, cv2.COLOR_BGR2RGB))

        

        last_img = img


if __name__ == "__main__":
    # The screenshots queue
    queue = Queue()  # type: Queue
    

    # 2 processes: one for grabing and one for saving PNG files
    Process(target=grab, args=(queue,)).start()
    Process(target=save, args=(queue,)).start()

The goal is to capture a game, while performing automated keyboard and mouse actions.

Answer 1

I have faced the same problem in trying to get high speed recording for games. This was the fastest solution I was able to find for Windows. The code is using raw buffer objects and leads to around ~27 FPS. I cannot find the original post on which this code is based, but if someone finds it I will add the reference.

Note that the framerate will significantly increase if you make the region smaller than 1920x1080.

"""
Alternative screen capture device, when there is no camera of webcam connected
to the desktop.
"""

import logging
import sys
import time
import cv2
import numpy as np

if sys.platform == 'win32':
    import win32gui, win32ui, win32con, win32api
else:
    logging.warning(f"Screen capture is not supported on platform: `{sys.platform}`")

from collections import namedtuple


class ScreenCapture:
    """
        Captures a fixed  region of the total screen. If no region is given
        it will take the full screen size.
        region_ltrb: Tuple[int, int, int, int]
            Specific region that has to be taken from the screen using
            the top left `x` and `y`,  bottom right `x` and `y` (ltrb coordinates).
    """
    __region = namedtuple('region', ('x', 'y', 'width', 'height'))

    def __init__(self, region_ltrb=None):
        self.region = region_ltrb
        self.hwin = win32gui.GetDesktopWindow()

        # Time management
        self._time_start = time.time()
        self._time_taken = 0
        self._time_average = 0.04

    def __getitem__(self, item):
        return self.screenshot()

    def __next__(self):
        return self.screenshot()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()
        if exc_type and isinstance(exc_val, StopIteration):
            return True
        return False

    @staticmethod
    def screen_dimensions():
        """ Retrieve total screen dimensions.  """
        left = win32api.GetSystemMetrics(win32con.SM_XVIRTUALSCREEN)
        top = win32api.GetSystemMetrics(win32con.SM_YVIRTUALSCREEN)
        height = win32api.GetSystemMetrics(win32con.SM_CYVIRTUALSCREEN)
        width = win32api.GetSystemMetrics(win32con.SM_CXVIRTUALSCREEN)
        return left, top, height, width

    @property
    def fps(self):
        return int(1 / self._time_average) * (self._time_average > 0)

    @property
    def region(self):
        return self._region

    @property
    def size(self):
        return self._region.width, self._region.height

    @region.setter
    def region(self, value):
        if value is None:
            self._region = self.__region(*self.screen_dimensions())
        else:
            assert len(value) == 4, f"Region requires 4 input, x, y of left top, and x, y of right bottom."
            left, top, x2, y2 = value
            width = x2 - left + 1
            height = y2 - top + 1
            self._region = self.__region(*list(map(int, (left, top, width, height))))

    def screenshot(self, color=None):
        """
            Takes a  part of the screen, defined by the region.
            :param color: cv2.COLOR_....2...
                Converts the created BGRA image to the requested image output.
            :return: np.ndarray
                An image of the region in BGRA values.
        """
        left, top, width, height = self._region
        hwindc = win32gui.GetWindowDC(self.hwin)
        srcdc = win32ui.CreateDCFromHandle(hwindc)
        memdc = srcdc.CreateCompatibleDC()

        bmp = win32ui.CreateBitmap()
        bmp.CreateCompatibleBitmap(srcdc, width, height)
        memdc.SelectObject(bmp)
        memdc.BitBlt((0, 0), (width, height), srcdc, (left, top), win32con.SRCCOPY)

        signed_ints_array = bmp.GetBitmapBits(True)
        img = np.frombuffer(signed_ints_array, dtype='uint8')
        img.shape = (height, width, 4)

        srcdc.DeleteDC()
        memdc.DeleteDC()
        win32gui.ReleaseDC(self.hwin, hwindc)
        win32gui.DeleteObject(bmp.GetHandle())

        # This makes sure that the FPS are taken in comparison to screenshots rates and vary only slightly.
        self._time_taken, self._time_start = time.time() - self._time_start, time.time()
        self._time_average = self._time_average * 0.95 + self._time_taken * 0.05

        if color is not None:
            return cv2.cvtColor(img, color)
        return img

    def show(self, screenshot=None):
        """ Displays an image to the screen. """
        image = screenshot if screenshot is not None else self.screenshot()
        cv2.imshow('Screenshot', image)

        if cv2.waitKey(1) & 0xff == ord('q'):
            raise StopIteration
        return image

    def close(self):
        """ Needs to be called before exiting when `show` is used, otherwise an error will occur.  """
        cv2.destroyWindow('Screenshot')

    def scale(self, src: np.ndarray, size: tuple):
        return cv2.resize(src, size, interpolation=cv2.INTER_LINEAR_EXACT)

    def save(self, path, screenshot=None):
        """ Store the current screenshot in the provided path. Full path, with img name is required.) """
        image = screenshot if screenshot is not None else self.screenshot
        cv2.imwrite(filename=path, img=image)


if __name__ == '__main__':
    # Example usage when displaying.
    with ScreenCapture((0, 0, 1920, 1080)) as capture:
        for _ in range(100):
            capture.show()
            print(f"\rCapture framerate: {capture.fps}", end='')

    # Example usage as generator.
    start_time = time.perf_counter()
    for frame, screenshot in enumerate(ScreenCapture((0, 0, 1920, 1080)), start=1):
        print(f"\rFPS: {frame / (time.perf_counter() - start_time):3.0f}", end='')

---

Edit

I noticed some small mistake in the window show function, and the self.screenshot calls in the __getitem__ and __next__ method. These have been resolved.

Next to the for example using the ScreenCapture as a context manager, I added an example of using it as a generator.