Uses ffmpeg to grab screen and outputs in Surface on pygame

ffmpeg_grab_to_pygame.py

from __future__ import annotations
from threading import Thread, Event
from queue import Queue
import subprocess

import pygame

MONITORS = {
    'left': (-1920, 0, 1920, 1080),
    'middle': (0, 0, 2560, 1440),  # presumably main monitor, hence offset is (0, 0)
    'right': (2560, 0, 1920, 1080),
}


def ffmpeg_thread(monitor: str, q: Queue, stop_ev: Event, w: int, h: int) -> None:
    sx, sy, sw, sh = MONITORS[monitor]
    proc = subprocess.Popen([
        'ffmpeg',
        '-hide_banner',
        '-loglevel', 'warning',
        '-f', 'gdigrab',
        '-probesize', '42M',
        '-framerate', '15',
        '-offset_x', f'{sx}',
        '-offset_y', f'{sy}',
        '-video_size', f'{sw}x{sh}',
        '-show_region', '1',
        '-i', 'desktop',
        '-vf', f'scale={w}:{h}',
        '-f', 'rawvideo',
        '-pix_fmt', 'rgb24',
        '-vcodec', 'rawvideo',
        '-',
    ], stdout=subprocess.PIPE)

    buf = b''
    framesize = w * h * 3
    while not stop_ev.is_set():
        chunk = proc.stdout.read(framesize)
        if not chunk:
            break
        buf += chunk
        while len(buf) >= framesize:
            q.put(buf[:framesize])
            buf = buf[framesize:]
    proc.terminate()
    proc.wait()


def main():
    grabwh = 854, 480
    ffmpeg_q = Queue()
    ffmpeg_ev = Event()
    ffmpeg_t = Thread(target=ffmpeg_thread, args=('left', ffmpeg_q, ffmpeg_ev, *grabwh))
    ffmpeg_t.start()

    pygame.init()
    pw, ph = 1280, 720
    screen = pygame.display.set_mode((pw, ph))
    screen.fill((0, 0, 0))
    clock = pygame.time.Clock()
    last_frame = None

    vx = 3
    vy = 2

    sx = 0
    sy = 0

    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                ffmpeg_ev.set()
                ffmpeg_t.join()
                return

        frame = last_frame
        while not ffmpeg_q.empty():
            frame = ffmpeg_q.get()
        if frame is not None:
            last_frame = frame
            surface = pygame.image.frombuffer(frame, grabwh, 'RGB')

            sx += vx
            sy += vy

            if sx < 0 or sx > pw - grabwh[0]:
                vx = -vx

            if sy < 0 or sy > ph - grabwh[1]:
                vy = -vy

            screen.fill((0, 0, 0))
            screen.blit(surface, (sx, sy))

        pygame.display.flip()
        clock.tick(60)


if __name__ == '__main__':
    main()