Webcam video to hdmi output

Support
1

I use my Logitec usb-webcam and the PYNQ-Z2 board. I want to create a video stream of the camera via hdmi out.

The code I am using is:

Capture_webcam_camera

from pynq.overlays.base import BaseOverlay
from pynq.lib.video import *
base = BaseOverlay(“base.bit”)

monitor configuration: 640*480 @ 60Hz

Mode = VideoMode(640,480,24)
hdmi_out = base.video.hdmi_out
hdmi_out.configure(Mode,PIXEL_BGR)
hdmi_out.start()

monitor (output) frame buffer size

frame_out_w = 1920
frame_out_h = 1080

camera (input) configuration

frame_in_w = 640
frame_in_h = 480

initialize camera from OpenCV

import cv2

cap = cv2.VideoCapture(0)

cap.set(cv2.CAP_PROP_FRAME_WIDTH, frame_in_w);
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, frame_in_h);

print("Capture device is open: " + str(cap.isOpened()))

Capture webcam video

while (True):
ret, frame = cap.read()

outframe = hdmi_out.newframe()
outframe[:] = frame
hdmi_out.writeframe(outframe)

cap.release()
cv2.destroyAllWindows()

The Problem is that the live video is starting, but it freezes in a couple of seconds and I get an Error

TypeError

TypeError Traceback (most recent call last)
in ()
5
6 outframe = hdmi_out.newframe()
----> 7 outframe[:] = frame
8 hdmi_out.writeframe(outframe)

TypeError: int() argument must be a string, a bytes-like object or a number, not ‘NoneType’

Does anyone know why exactly this occurs?
Thanks :slight_smile:

2

Usually this is a result of either the webcam or the kernel driver for it crashing. Is there anything on dmesg that indicates what might have happened?

Peter

3

As peter said it generally happens when camera is unable to transfer the image. You could just use a if block before display the image, it will keep running the window even if there is a frame skip:

ret, frame = cap.read()
if ret:
   outframe = hdmi_out.newframe()
   outframe[:] = frame
   hdmi_out.writeframe(outframe)
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