录制下来的视频不能播放

# Image Writer Example
#
# USE THIS EXAMPLE WITH A USD CARD! Reset the camera after recording to see the file.
#
# This example shows how to use the Image Writer object to record snapshots of what your
# OpenMV Cam sees for later analysis using the Image Reader object. Images written to disk
# by the Image Writer object are stored in a simple file format readable by your OpenMV Cam.
THRESHOLD = (0, 35, -16, 13, -15, 23)
import sensor, image, pyb, time
from pyb import UART

record_time = 10000 # 10 seconds in milliseconds

sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QQQVGA)
sensor.skip_frames(time = 2000)
clock = time.clock()

uart = UART(3, 9600)
img_writer = image.ImageWriter("/stream.bin")

# Red LED on means we are capturing frames.
red_led = pyb.LED(1)
red_led.off()

start = pyb.millis()
while pyb.elapsed_millis(start) < record_time:
    clock.tick()
    #img = sensor.snapshot()
    # Modify the image if you feel like here...
    img = sensor.snapshot().binary([THRESHOLD])
    line = img.get_regression([(100,100,0,0,0,0)], robust = True)
    if (line):
        img.draw_line(line.line(), color = 127)
        if line.theta()>90:
            theta_err = 270 - line.theta()
        else:
            theta_err = 90 - line.theta()
        #print(line.magnitude(),line.theta(),line.rho())
        img_data = bytearray([theta_err])
        uart.write(img_data+'\r\n')
        #led3.on()
        print(theta_err,line.theta())
        #print(clock.fps())
    img_writer.add_frame(img)
    print(clock.fps())

img_writer.close()

# Blue LED on means we are done.
red_led.off()
blue_led = pyb.LED(3)
blue_led.on()
#blue_led.off()

print("Done")
while(True):
    clock.tick()
#img = sensor.snapshot()
# Modify the image if you feel like here...
    img = sensor.snapshot().binary([THRESHOLD])
    line = img.get_regression([(100,100,0,0,0,0)], robust = True)
    if (line):
        img.draw_line(line.line(), color = 127)
        if line.theta()>90:
            theta_err = 270 - line.theta()
        else:
            theta_err = 90 - line.theta()
    #print(line.magnitude(),line.theta(),line.rho())
        img_data = bytearray([theta_err])
        uart.write(img_data+'\r\n')
    #led3.on()
        print(theta_err,line.theta())

在做寻线小车时候，想把识别直线的过程录制下来，方便调参数，应该怎么添加录像。