Python OpenCV cv2.VideoWriter Error

Question

I'm trying to export the data coming from a thermal camera but I get an error message that says

error: /build/opencv-ISmtkH/opencv-2.4.9.1+dfsg/modules/highgui/src/cap_ffmpeg.cpp:238: error: (-215) image->depth == 8 in function writeFrame

Can someone look at what I'm doing and tell me what I'm doing wrong? I followed and example pretty closely so I don't understand what this error means or why it's happening.

o = camera.add_overlay(np.getbuffer(a), size=(320,240), layer=3, alpha=int(alpha), crop=(0,0,80,60), vflip=flip_v)

filename = time.strftime("%Y.%m.%d  %H.%M.%S", time.localtime()) + ".avi"
fourcc =  cv2.cv.CV_FOURCC('I','4','2','0')
out = cv2.VideoWriter(filename, fourcc, fps, (width, height))

try:
  time.sleep(0.2) # give the overlay buffers a chance to initialize
  with Lepton(device) as l:
    last_nr = 0
    while True:
      _,nr = l.capture(lepton_buf)

      out.write(lepton_buf)

      if nr == last_nr:
        # no need to redo this frame
        continue
      last_nr = nr
      cv2.normalize(lepton_buf, lepton_buf, 0, 65535, cv2.NORM_MINMAX)
      np.right_shift(lepton_buf, 8, lepton_buf)
      a[:lepton_buf.shape[0], :lepton_buf.shape[1], :] = lepton_buf
      o.update(np.getbuffer(a))
except Exception:
  traceback.print_exc()
finally:
  camera.remove_overlay(o)

Answer 1

You need to change out.write(lepton_buf) to out.write(np.uint8(lepton_buf))

What you're trying to write isn't a number and that's what's confusing it.

Answer 2

Several suggestions to try

Try a more common codec:

fourcc=cv2.VideoWriter_fourcc('X', 'V', 'I', 'D')

make sure your video dimensions fit the image dimensions. Try swapping width and height, the order of these can be confusing.

height,width,channels=lepton_buf.shape

or specify directly width and height for your video:

out = cv2.VideoWriter(filename, fourcc, 8.0, (60, 80))

as stated before by @Crystal, make sure you convert your image data to data type 'uint8'

Try saving to a 'fresh' file name. Sometimes opencv videowriter silently fails saving to a file that hasn't been properly released from a previous access.

finally, release your file when done writing frames!

out.release()