I am trying to visualize a live stream video and at the same time i would like to preview last few minutes from it, trim it or even preview multiple times.

The Problem is although I can see the post request is triggered but still it doesn’t work

########## Generator function #######

def gen(vid_source, cam_idx, preview=False):
    '''
    Video streaming generator function
    vid_source: source to capture from
    cam_idx: index of the displayed camera
    '''
    global match_folder, recording_folder, events_folder
    if preview==False:
        recording_folder = './records'
        live_stream_record_path = f'{recording_folder}/cam_{cam_idx}.mp4' #where the live stream will be recorded
    cap = cv2.VideoCapture(vid_source)
    fps = cap.get(cv2.CAP_PROP_FPS)
    width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
    height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
    
    if preview==False:
        live_stream_vid_writer = cv2.VideoWriter(live_stream_record_path, cv2.VideoWriter_fourcc(*"mp4v"), fps, (int(width), int(height)))
    frame_num = 0
    # Read until video is completed
    while(cap.isOpened()):
      # Capture frame-by-frame
        ret, img = cap.read()
        if ret == True:
            if preview==False:
                live_stream_vid_writer.write(img)

                frame_num +=1
                if os.path.exists(f'./records/preview{cam_idx}_imgs')==False:
                    os.mkdir(f'./records/preview{cam_idx}_imgs')

                cv2.imwrite(f'./records/preview{cam_idx}_imgs/{frame_num}.jpg',img)


            img = cv2.resize(img, (0,0), fx=0.5, fy=0.5)
            frame = cv2.imencode('.jpg', img)[1].tobytes()
            yield (b'--framern'b'Content-Type: image/jpegrnrn' + frame + b'rn')
            time.sleep((1/fps))
        else:
            break


############# routes ##############
@app.route('/cam1_video_feed')
async def cam1_video_feed():
    return Response(gen('1.mp4',0),
                    mimetype='multipart/x-mixed-replace; boundary=frame')





############## html #################
<img src="{{ url_for('cam1_video_feed') }}" width='200px' height='200px'>```