video_capture.py

import cv2
import time


def video_init(is_2_write=False,save_path=None):
    writer = None
    cap = cv2.VideoCapture(0)
    height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)#default 480
    width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)#default 640

    # width = 480
    # height = 640
    # cap.set(cv2.CAP_PROP_FRAME_WIDTH, width)
    # cap.set(cv2.CAP_PROP_FRAME_HEIGHT, height)

    '''
    ref:https://docs.opencv.org/master/dd/d43/tutorial_py_video_display.html
    FourCC is a 4-byte code used to specify the video codec. 
    The list of available codes can be found in fourcc.org. 
    It is platform dependent. The following codecs work fine for me.
    In Fedora: DIVX, XVID, MJPG, X264, WMV1, WMV2. (XVID is more preferable. MJPG results in high size video. X264 gives very small size video)
    In Windows: DIVX (More to be tested and added)
    In OSX: MJPG (.mp4), DIVX (.avi), X264 (.mkv).
    FourCC code is passed as `cv.VideoWriter_fourcc('M','J','P','G')or cv.VideoWriter_fourcc(*'MJPG')` for MJPG.
    '''

    if is_2_write is True:
        #fourcc = cv2.VideoWriter_fourcc('x', 'v', 'i', 'd')
        #fourcc = cv2.VideoWriter_fourcc('X', 'V', 'I', 'D')
        fourcc = cv2.VideoWriter_fourcc(*'divx')
        if save_path is None:
            save_path = 'demo.avi'
        writer = cv2.VideoWriter(save_path, fourcc, 30, (int(width), int(height)))

    return cap,height,width,writer

def video_capture(is_2_write=False,save_path=None):
    #----var
    frame_count = 0
    FPS = "0"
    #----video streaming init
    cap, height, width, writer = video_init(is_2_write=is_2_write,save_path=save_path)


    while (cap.isOpened()):


        #----get image
        ret, img = cap.read()

        if ret is True:
            #----image processing
            if frame_count == 0:
                t_start = time.time()
            frame_count += 1
            if frame_count >= 10:
                FPS = "FPS=%1f" % (10 / (time.time() - t_start))
                frame_count = 0

            # cv2.putText(影像, 文字, 座標, 字型, 大小, 顏色, 線條寬度, 線條種類)
            cv2.putText(img, FPS, (10, 50), cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 255, 0), 3)

            #----image display
            cv2.imshow("demo by JohnnyAI", img)

            #----image writing
            if writer is not None:
                writer.write(img)

            #----'q' key pressed?
            if cv2.waitKey(1) & 0xFF == ord('q'):
                break
        else:
            print("get image failed")
            break

    #----release
    cap.release()
    if writer is not None:
        writer.release()
    cv2.destroyAllWindows()


if __name__ == "__main__":
    save_path = r"E:\demo.avi"
    video_capture(is_2_write=True, save_path=save_path)