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• OpenCV (3.3.0) returns fail on VideoCapture with Video but works with Webcam [OS X]

  1er novembre 2017, par njoye

  Thanks for reading already, I’ve been trying to get this to work for a day and I didn’t get closer to the solution.

  I’m trying to get this object tracker to work. When I use a video from my webcam (with : python object-tracker-single.py -d 0, everything works as expected.

  But as soon as I’m trying to use a video file (i’ve tried different formats : .mp4, .mkv & .avi. I also tried to use the file given in the repository, that didn’t work as well. To see if there is a File not found-Error, I passed an invalid path to the function and an error got printed, that has not been printed when I used the other videos. So the file(s) i’m using is(/are) valid and not corrupted.

  I installed dlib through homebrew following this article and compiled OpenCV from the official source. This is the CMakeCache.txt that CMake spit out. After the first time I compiled it, I added opencv_contrib to the mix, thinking that it could help (I also think that I actually needed it), but that didn’t fix the problem.

  This is the code I’m having problems with :

  # Create the VideoCapture object
  
  cam = cv2.VideoCapture(source)
  
  
  
  # If Camera Device is not opened, exit the program
  
  if not cam.isOpened():
  
      print "Video device or file couldn't be opened"
  
      exit()
  
  
  
  print "Press key `p` to pause the video to start tracking"
  
  while True:
  
      # Retrieve an image and Display it.
  
      retval, img = cam.read() #<-- this returns false when trying to read a video 
  
      if not retval:
  
          print "Cannot capture frame device"
  
          exit()

  At the marked line, retval equals False and image equals None.
  It would already help me if I could somehow debug this behavior, but I didn’t find any way of doing so.

  I found that many Windows Users had problems with missing ffmpeg support, but that is not the case for me, since I used ffmpeg in previous (not OpenCV-related) projects and CMakeCache.txt reports that ffmpeg has been found and the compilation succeeded.

  I also tried using a fully qualified file-name for the video file, which either resulted in Video device or file couldn't be opened or the given problem.

  If you have any idea how this problem can be completely resolved, have an Idea on how to solve it or can provide me with a way of properly debugging this behavior, I’d be super glad to here it !

  Thanks already !

  -

  System : MacBook Pro (macOS Sierra 10.12.6)

  OpenCV Version : 3.3.0

  Dlib Version (not necessary imo, but hey) : 19.4.0

  Edit 2
  Output of cmake -DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib-master/modules ../ >> result.txt : pastebin

• How to get a list of video devices with a particular VendorID and/or ProductID using FFmpeg (on Mac OS)

  26 mai 2020, par mcgregor94086

  The master task :

  



  I am writing software for a multiple USB camera array. The camera may be connected to a CPU that has other USB cameras builtin or attached. I need to capture one 1920x1080 JPG image from EACH of MY array's cameras into a directory of images - but I need to EXCLUDE any OTHER cameras when taking pictures.

  



  Right now I am trying to implement for MacOS, but in the future I will be implementing for Windows, Linux, iOS and Android.

  



  What is known :

  



  I know the VendorID, ProductID and UniqueID (reported by the MacOS USB system System Hardware Report) for each of the cameras in the camera array.

  



  UNIQUESKY_CAR_CAMERA #5:

  Model ID: UVC Camera VendorID_7119 ProductID_2825
  Unique ID:    0x143400001bcf0b09

UNIQUESKY_CAR_CAMERA #6:

  Model ID: UVC Camera VendorID_7119 ProductID_2825
  Unique ID:    0x143300001bcf0b09


  



  The problem code :

  



  I made the following call to FFmpeg

  



  ffmpeg -nostdin -hide_banner -an -sn -dn  -f avfoundation -list_devices true -I 1


  



  I received the following result in stderr :

  



      [AVFoundation indev @ 0x7fc870e21800] AVFoundation video devices:
    [AVFoundation indev @ 0x7fc870e21800] [0] FaceTime HD Camera (Built-in)
    [AVFoundation indev @ 0x7fc870e21800] [1] UNIQUESKY_CAR_CAMERA #5
    [AVFoundation indev @ 0x7fc870e21800] [2] UNIQUESKY_CAR_CAMERA #6
    [AVFoundation indev @ 0x7fc870e21800] [3] Capture screen 0
    [AVFoundation indev @ 0x7fc870e21800] [4] Capture screen 1
    [AVFoundation indev @ 0x7fc870e21800] AVFoundation audio devices:
    [AVFoundation indev @ 0x7fc870e21800] [0] MacBook Pro Microphone
    1: Input/output error


  



  Of these devices listed in the output, I happen to know (in this particular TEST CASE) that the cameras in my test array, are only these two :

  



  [1] UNIQUESKY_CAR_CAMERA #5
[2] UNIQUESKY_CAR_CAMERA #6


  



  With this knowledge, I can select the indices (1 2) that I need, and then use the following code to capture an image from each :

  



  for i in 1 2; 
do
    ffmpeg  -y -hide_banner  -f avfoundation  -r 15 -video_size 1920x1080 -i 1  -f image2 -qscale:v 1 -qmin 1 -qmax 1 -frames:v 1 img$i.jpg;
done



  



  Unfortunately, in production use (i.e. outside of this test case), I CAN NOT rely on cameras all identifying themselves with the same TEXT "name" prefix (e.g. "UNIQUESKY_CAR_CAMERA"), so I can't just use grep to select the ones I want.

  



  But I CAN be sure that I will know their VendorID, ProductID and UniqueIDs.

  



  So, IF I could get

  



  ffmpeg  -nostdin -hide_banner -an -sn -dn  -f avfoundation -list_devices true -I 1


  



  to also list the VendorID and ProductID, then I could grep for those values.

  



  Is this solution possible ? I can't find syntax in the documentation or examples for how to set such limits.

  



  ALTERNATIVELY : if I could specify to FFmpeg -list_devices to limit the output list to just those with my specified VendorID and ProductIDs then I could easily get the list of device indices I will need for the succeeding image extraction.

  



  Is this solution possible ? I can't find syntax in the documentation or examples for how to set such limits.

  



  Special Note :
  
The cameras I am using are all 1920x1080, and that resolution is necessary for my application. As has been noted by many Mac users on the web, other image capture programs (such as imagesnap) sometimes capture images at lower resolution (1024x720) than the cameras are capable of, and will not capture images at higher resolutions such as (1920x1080). For this reason, and because it is available on ALL the OS platforms of interest to us, I chose to use FFmpeg.

  


• how can I assign unique AVFoundation camera device names ?

  28 avril 2023, par mcgregor94086

  Short summary :
I have a USB multi-camera array device. According to system_profiler, each of these webcams share the same name : "USB Camera". I have no unique name I can use with FFMPEG AVFoundation and get images from that specific camera. How can I tell FFMPEG the specific camera that I want (each has a unique USB path that I normally use to identify a specific camera.

  


  I can solve this problem on Linux, but I can't figure out how to do it on macOS.

  


  How I might do this on Linux
I know the unique USB Path to each camera, and I would like to use this to assign a unique Name that I can address using FFMPEG when taking images. On Linux I can use the udev system to make those assignments,

  


  In Linux, I can reassign a new unique camera name using /etc/udev/rules.d/60-v4l.rules. with something like this :

  


  SUBSYSTEMS=="usb", ENVID_VENDOR_ID=="0bda", ENVID_MODEL_ID=="5829", ENVID_PATH_TAG==platform-fd500000_pcie-0000_01_00_0-usb_1_4_5_1_3_1_1, ENVID_V4L_PRODUCT="Cam_00"
SUBSYSTEMS=="usb", ENVID_VENDOR_ID=="0bda", ENVID_MODEL_ID=="5829", ENVID_PATH_TAG==platform-fd500000_pcie-0000_01_00_0-usb_1_4_5_1_3_1_3, ENVID_V4L_PRODUCT="Cam_01"
...

  


  More details :
Of course macOS doesn't work this way, as it uses AVFoundation to address video devices.

  


  When I attach the device I see that 16 new cameras now appear when I type query system_profiler SPCameraDataType, it prints the output shown further below

  


  You may notice that there are 16 cameras all named "USB Camera :" but system_profiler is reporting that each has a "Unique ID :" that is different for each camera. This Unique ID is composed of a unique USB Path (e.g. '0x1441311') concatenated with the "Vendor ID" ('00bda') and product ID ('5829') all expressed in hexadecimal.

  


  Unfortunately, this means every camera has the same generic name in iPhoto, and when specifying the input camera in FFMPEG with AVFoundation syntax, I can't seem to indicate which specific camera I want.

  


  I want to take 1 photo from each camera in a specific order. I have a table that maps each camera's USB Path to a desired name that would make it easy for me to trigger the camera captures in the sequence I desire.

  


  In Linux, I can reassign a new unique camera name using /etc/udev/rules.d/60-v4l.rules.

  


  SUBSYSTEMS=="usb", ENVID_VENDOR_ID=="0bda", ENVID_MODEL_ID=="5829", ENVID_PATH_TAG==platform-fd500000_pcie-0000_01_00_0-usb_1_4_5_1_3_1_1, ENVID_V4L_PRODUCT="Cam_00"
SUBSYSTEMS=="usb", ENVID_VENDOR_ID=="0bda", ENVID_MODEL_ID=="5829", ENVID_PATH_TAG==platform-fd500000_pcie-0000_01_00_0-usb_1_4_5_1_3_1_3, ENVID_V4L_PRODUCT="Cam_01"
...

  


  % system_profiler SPCameraDataType

  


  Camera :

  


  USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144131100bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144200000bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144141400bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144131300bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144141300bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144121200bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144121400bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144133000bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144131200bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144141100bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144143000bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144121300bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144110000bda5829

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144141200bda5829

FaceTime HD Camera (Built-in):

  Model ID: UVC Camera VendorID_1452 ProductID_34068
  Unique ID: 0x8020000005ac8514

USB Camera:

  Model ID: UVC Camera VendorID_3034 ProductID_22569
  Unique ID: 0x144300000bda5829


  


  MacBook Pro, OS X 10.11
Posted on Apr 27, 2023 10:49 PM
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