Recording video using video.py from examples

My configuration is Raspberry Pi 4/ 2G (latest buster) python3.7.1. Im using modified file video.py from examples:

def callback(data):
    buff = Dcam.buffer(data)
    print("one frame len %d" % buff.length)
    file = buff.userdata
    buff.as_array.tofile(file)
    return 0

if __name__ == "__main__":
    try:
        camera = Dcam.mipi_camera()
        print("Open camera...")
        camera.init_camera()
        **file = open("/home/pi/test.h264", "wb")**
        # Need keep py_object reference
        file_obj = ctypes.py_object(file)
        camera.start_video_stream(callback, file_obj)
        time.sleep(10)
        camera.stop_video_stream()
        file.close()
        print("Close camera...")
        camera.close_camera()
    except Exception as e:
        print(e)

My observations only on using python examples (elf programs that recording video that you provided have no issue):

output file is corrupted, it's seems like it recorded 5sec instead of 10sec .
quality set bandwidth to 17MB/s is ....poor when on camera there is fast movement

Is this normal ? I can provide my video for better see this "artifacts" and issue that I've described. Could you please support? What I'm missing to get python video script working as well as veye_raspivid .

test.zip

veyeimaging / raspberrypi

Recording video using video.py from examples #4