Mlx90640 no video stream

asked 2020-10-01 13:53:34 -0500

firebladed gravatar image

updated 2020-10-02 09:48:20 -0500

I am having issues getting a video stream from a Mlx90640 i2c thermal camera on a raspberry pi running ubuntu 20 and i have a recently compiled version of opencv from github

i have the camera connected and can stream the image to the display using ffmpeg

ffmpeg -f rawvideo -pixel_format y16be -video_size "32x26" -i /dev/video0 -vf scale=800:640 -f fbdev -pix_fmt bgra /dev/fb0

if try to use a device no i get

>>> import  cv2
>>> vs = cv2.VideoCapture(0)
[ WARN:0] global /home/ubuntu/opencv/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

and if i try to access by device path after a wait it gives no error but is not open

>>> vs = cv2.VideoCapture("/dev/video0")
>>> vs.isOpened()

its v4l details are

v4l2-ctl -d /dev/video0 --all

Driver Info:
    Driver name      : video-i2c
    Card type        : I2C 1-51 Transport Video
    Bus info         : I2C:1-51
    Driver version   : 5.4.55
    Capabilities     : 0x85200001
            Video Capture
            Extended Pix Format
            Device Capabilities
    Device Caps      : 0x05200001
            Video Capture
            Extended Pix Format

Priority: 2

Video input : 0 (Camera: ok)

Format Video Capture:
    Width/Height      : 32/26
    Pixel Format      : 'Y16 -BE' (16-bit Greyscale BE)
    Field             : None
    Bytes per Line    : 64
    Size Image        : 1664
    Colorspace        : Raw
    Transfer Function : Default (maps to None)
    YCbCr/HSV Encoding: Default (maps to ITU-R 601)
    Quantization      : Default (maps to Full Range)
    Flags             :

Streaming Parameters Video Capture:
    Capabilities     : timeperframe
    Frames per second: 64.000 (64/1)
    Read buffers     : 1

having had issues with i2c cameras before i did some checking and the V4L2_PIX_FMT_Y16_BE pixel format is not present in cap_v4l.cpp

is this likely to be the cause of this error? if not what can i do to diagnose the problem?


further testing using v4l2-loopback and ffmpeg to convert from V4L2_PIX_FMT_Y16_BE to V4L2_PIX_FMT_Y16

 ffmpeg -f rawvideo -pixel_format y16be -video_size "32x26" -i /dev/video0 -f v4l2 -vcodec rawvideo -pix_fmt y16 /dev/video1

it then works correctly which suggests to be that is not handling something correctly and should be producing "VIDEOIO ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV" but isnt

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iirc only the gstreamer or ffmpeg backend accepts like "/dev/video0" you could try:

cv2.VideoCapture("/dev/video0", cv2.CAP_FFMPEG)
berak gravatar imageberak ( 2020-10-02 04:14:13 -0500 )edit

no luck there

firebladed gravatar imagefirebladed ( 2020-10-02 08:08:47 -0500 )edit