I am trying to capture an image frame from a USB camera using opencv. However I am always getting a black frame. I have read many posts with this issue and tried all the suggestions but nothing worked for me.
I started using the code discussed here:
http://opencv-users.1802565.n2.nabble.com/Using-USB-Camera-td6786148.html
I have tried including the method cvWaitKey(1000) after many 'critical' sentences. As you can see the waiting value is very high (1000).
I have also tried to save the image frame and, equally, it is a black image.
I am using the following system:
OpenCV 2.2.0
Windows 7, 32 bits
Visual Studio 2010 (C++)
a board usb camera (which I do not know the manufacturer)
The usb camera works well with AMCAP.EXE 1.00.
Could it be because of the camera drivers being used by Windows? Could I change to other drivers that work better for OpenCV 2.2.0?
Thanks
Ok. As I promised to your request in the comments, and sorry to keep you waiting, really been busy. Barely had time to post this answer too. But here it is:
This is me simulating that opencv is capturing black image. On the output window, which I had asked you in the comments about what it says, shows that there is an error.
After investigating, I realised that it is due to the camera's available format:
Of cuz, this is a lousier camera. If you have a better camera like the logitech one, you can see that the format available is so much more.
There are lots of methods, you can try some thing like
capture.set(CV_CAP_PROP_FRAME_WIDTH , 640);
capture.set(CV_CAP_PROP_FRAME_HEIGHT , 480);
capture.set (CV_CAP_PROP_FOURCC, CV_FOURCC('B', 'G', 'R', '3'));//diff from mine, using as example
then the webcam will be able to snap. This webcam is bit faulty, hence the image snapped is not that beautiful.
Hope this is your problem. but it may not be the case too. I like debugging problems, but I can't put down all the possible causes that this happen for you as I am really busy, as you asked for an example, this is one of them. Cheers. If you could tell me what you output window error says, I probably can help more.
EDIT(to answer more in your comments):
Ok, I want you to try a few things:
1)First, instead of using cvQueryFrame, or similar capturing methods, I want you to try use that webcam to capture a video instead. Wait up to maybe say 10 secs to see if it's successful. Reason being, some cameras(lower quality ones) take quite a while to warm up and the first few frames they capture may be an empty one.
2) If the step one doesn't work, try typing
cout << cv::getBuildInformation() << endl;
and paste the results for media I/O and Video I/O? I want to see the results. I would suspect your library dependencies too, but since you said it works with a logitech camera, I doubt that's the case. Of course, there's always a chance it's due to that the camera is not compatible to OpenCV. Does the camera have any brands by the way?
3) Alternatively, just search for usb drivers online and install it, I had a friend who did this for a similar problem, but not sure the process of that.
The first thing, I would suggest is, visit this link and check your camera is working or not
http://www.youronlinemirror.com/
if yes, then go through below link to get started with things, you ll also find a good opencv c++ code out there, the code which you are using is of opencv1 api's c code, I would rather encourage you to go for c++ than the old version of opencv.
http://opencv-srf.blogspot.in/2011/09/capturing-images-videos.html
if you want an answer for your code, then, its simple, as you are saying its giving a black screen, which happened in my case when i started things out with opencv,
it isnt able to take the data from device, so, try this, it might work, as it did for me.
add
cvQueryFrame( capture );
before
IplImage* frame = cvQueryFrame( capture );
I went through the same problem as yours. Then I just changed the version from 3.1.0 to 2.4.13, then my webcam works! No more black images. I guess the 3 version is not compatible with the vs15. Thinking you may have already solved the problem long ago. But just post to let others know if they happen to have the same issue.
Even I faced the same black screen problem while running OpenCV-related programs. So instead of using USB cam I used mobile camera which worked perfectly fine. Use Google apps such as DroidCam (install DroidCam on mobile as well as on laptop/PC) to connect your mobile camera to laptop through Wi-Fi.
Related
I'm using a Raspberry Pi 3B+ with an equivalent board to the Auvidea B101 which is a HDMI to MIPI bridge. The board works correctly and I can save images using the code from my gist ( https://gist.github.com/danriches/80fadc21b5f1b0ca8ba725a8dd598710 ). However when I try to use OpenCV 4.2.0 (compiled locally and samples all work!) I get a segfault as detailed in the comments section of the gist. I can't for the life of me work out why though. If someone has a B101 or equivalent that uses the TC358743 chipset and has it working with OpenCV I'd be greatly appreciative if you have any advice or suggestions.
This all needs to work as fast as possible so apps calling apps is no good, I need to process the buffer and write it to a gstreamer pipe eventually. In fact if I could take the jpeg I get out the original code at line 832 and pass it to an instance of gst-rtsp-server then I'd be a happy man.
Any takers??
Dan
My goal is as follows: I have to read in a video that is stored on the sd card, process it frame for frame and then store it in a new file on the SD card again，In each image to do image processing.
At first I wanted to use opencv for android but I did not seem to be able to read the video
here.
I am guessing you already know that doing this on a mobile device or any compute limited devices is not ideal, simply because video manipulation is very computer intensive which translates to slow execution and heavy battery usage on many devices. If you do have the option to do the processing on the server side it is definitely worth considering.
Assuming that for your use case you need to do it on the mobile device, then OpenCV on Android will now allow you to read in a video and access each frame - #StephenG mentions this in his answer to the question you refer to above.
In the past, functionality like this did not get ported to the Android OpenCv as the guidance was to use ffmpeg for frame grabbing on Android devices.
According to more recent documentation, however, this should be available for Android now using the VideoCapture class (note I have not used this myself...):
http://docs.opencv.org/java/2.4.11/org/opencv/highgui/VideoCapture.html
It is worth noting that OpenCV Android examples are all currently based around Eclipse and if you want to use Studio, getting things up an running initially can be quite tricky. The following worked for me recently, but as both studio and OpenCV can change over time you may find you have to do some forum hunting if it does not work for you:
https://stackoverflow.com/a/35135495/334402
Taking a different approach, you can use ffmpeg itself, in a wrapper in Android, for tasks like this.
The advantage of the wrapper approach is that you can use all the usual command line syntax and there is a lot of info on the web to help you get the right parameters.
The disadvantage is that ffmpeg was not really designed to be wrapped in this way so you do sometimes see issues. Having said that it is a common approach now and so long as you choose a well used wrapper library you should at least have a good community to discuss any issues you come across with. I have used this approach in a hand crafted way in the past but if I was doing it again I would use one of the popular examples such as:
https://github.com/WritingMinds/ffmpeg-android-java
I've got an application with a Raspberry Pi running Debian that is pretty performance demanding and I am trying to avoid starting X when booting and jumping directly into the program. This works fine, but if I would like to use the 'imshow' function in OpenCV, it does not work correctly, instead it says 'GTK-Warning: cannot open display" and exits the program.
Is it feasible to display a fullscreen image/video capture with opencv using imshow or any other function without X, or is it entirely dependent on the X?
Thanks,
For clarification, there is a monitor, it just shows the terminal prompt instead of a desktop. So the raspberry pi is getting an image to a screen at the correct resolution, I guess what I don't understand is what X11 does for opencv as far as handling of the window/image? I imagine a lot that cant be easily replicated.
But maybe a lightweight X11 alternative would be the best way to go if there's not another option, thanks for the tip.
Well, obviously the video output has to go somewhere... You could try Xvfb as a lightweight alternative to a full X11 instance.
I have never ever asked this kind of question on StackOverflow before, and I wonder if you could help me guys because it is a "bit" vague.
I have to design a project that uses Teensy (simple ARM platform) for getting data from IR camera (Flir, resolution 80x60) over SPI, and streaming these data to Linux/Windows running machine (through USB-serial) and doing something simple with OpenCV.
THE PROBLEM: The project lacks some "inovation". It should not be something very complicated, but rather different approach, or trying something new.
Do you have recommendations/tutorials/books/experience with working with above mentioned things? OR do you see a potential for teying something new?
You might want to check out the OpenCV Cookbook for some ideas.
There is a project using this FLIR with a Teensy. It provides a thermal image using a small LCD screen (without any aditional computer).
https://hackaday.io/project/8994-diy-thermocam
So, the teensy can get data through spi.
Can the teensy send data through usb then ? Probably but you will have to check if the rate is high enough
.
Using OpenCV directly on teensy is not possible because of size of library. But you can probably make some basic image processing if the code is small enough.
The FLIR Lepton can be directly interfaced with Linux or Windows computer, so I don't really see the use of Teensy.
I would recommend a Raspberry Pi to interface the FLIR Lepton and then do some image processing. It's well documented on the web.
I'm writing LabVIEW software that grabs images from an IMAQ compatible GigE camera.
The problem: This is a collaborative project, so I only have intermittent access to the actual camera.I'd like to be able to keep developing this software even when the camera isn't present.
Is there a simple/fast way to create a virtual or dummy IMAQ camera in software? Ideally I'd like the dummy camera grab frames from an AVI or a stack of JPEG's. Something like this must exist, I just can't find it on Google.
I'm looking for something that won't take very long (e.g.< 2 hours effort) and that is abstracted away through the standard LabVIEW IMAQ interface, so that my software won't know or care whether its dealing with a dummy camera or an actual camera.
You can try this method using LabVIEW classes:
Hardware Emulation Using LabVIEW Classes
If you have the IMAQdx driver, you might consider just buying a cheap USB webcam for $10.
Use the IMAQdx driver (assuming you have it), and then insert the Vision Acquisition Express VI, and you can choose AVIs or even pics as a source.
Something like this: GigESim is a camera emulation software. Unfortunately it is proprietary and too expensive (>$500) for my own needs, but perhaps others will find this link useful.
Anyone know of a viable Open Source alternative?
There's an IP Camera emulator project that emulates IP camera with python. I haven't used it myself so i don't know if it can be used by IMAQ.
Let us know if it's good for you.
I know this question is really old, but hopefully this answer helps someone out.
IMAQdx also works with Windows DirectShow devices. While normally these are actual physical capture devices (think USB Webcams), there is no necessity that they have to be.
There are a few different pre-made options available on the web. I found using Open Broadcaster Studio and this Virtual Cam plugin to be easy enough. Basically:
Download and install both.
Load your media sources in the sources list.
Enable the VirtualCam stream (Tools > VirtualCam). Press Start.