cam.isOpened() returns true, but cam.read() returns (false, None)

[dhaval-khatri1996]

openCv python version 4.5.5. Camera module waveshare OV9281-110 I am working with raspberry-pi model 4-B with latest bullseye OS.

I am able to capture image using libcamera-still -o test.png command but when I try to read an image with opencv it returns None. The output for cam.isOpened() is true but cam.grab() and cam.read() return false and (false,None) respectively.

Code:

import cv2
cam_port = 0
cam = cv2.VideoCapture(cam_port)
print(cam.isOpened())
print(cam.grab())
print(cam.read())
cam.release()

Output:

True
False
(False, None)

camera info

~ $ v4l2-ctl --device /dev/video0 --all

Driver Info:
	Driver name      : unicam
	Card type        : unicam
	Bus info         : platform:fe801000.csi
	Driver version   : 5.15.56
	Capabilities     : 0xa5a00001
		Video Capture
		Metadata Capture
		Read/Write
		Streaming
		Extended Pix Format
		Device Capabilities
	Device Caps      : 0x25200001
		Video Capture
		Read/Write
		Streaming
		Extended Pix Format
Media Driver Info:
	Driver name      : unicam
	Model            : unicam
	Serial           : 
	Bus info         : platform:fe801000.csi
	Media version    : 5.15.56
	Hardware revision: 0x00000000 (0)
	Driver version   : 5.15.56
Interface Info:
	ID               : 0x03000005
	Type             : V4L Video
Entity Info:
	ID               : 0x00000003 (3)
	Name             : unicam-image
	Function         : V4L2 I/O
	Flags         : default
	Pad 0x01000004   : 0: Sink
	  Link 0x02000007: from remote pad 0x1000002 of entity 'ov9281 10-0060': Data, Enabled, Immutable
Priority: 2
Video input : 0 (unicam-image: ok)
Format Video Capture:
	Width/Height      : 640/480
	Pixel Format      : 'BGR3' (24-bit BGR 8-8-8)
	Field             : None
	Bytes per Line    : 1920
	Size Image        : 921600
	Colorspace        : sRGB
	Transfer Function : sRGB
	YCbCr/HSV Encoding: ITU-R 601
	Quantization      : Full Range
	Flags  

[dhaval-khatri1996]

could someone help me out? I tried building opencv from source and still the same thing.

[asmorkalov]

Duplicate: https://github.com/opencv/opencv/issues/22820

[y1174804262]

你们可以尝试使用 picamera2，请参考https://blog.csdn.net/zhangmou_9008/article/details/134047114上面的3.1 you kan try to use picamera2,please show the blog's 3.1 :https://blog.csdn.net/zhangmou_9008/article/details/134047114