Stack Overflow
Stack Overflow

Questions tagged [v4l]

v4l ("Video For Linux") is a video capture infrastructure provided by the linux kernel. the historic "v4l" has been obsoleted by the "v4l2" ("Video for Linux 2") infastructure and has been removed from the linux-kernel starting with 2.6.38.

52 questions
0
votes
0 answers

Decode MJPEG image on live stream

I am trying to view live video from my webcam. I can draw the image to a window using OpenGL, get the frames in YUV and convert them on the fly into RGB. I can convert YUV colors into RGB easily, as well as I can get a pointer to the data from the…
Gabe Rundlett
  • 87
  • 8
0
votes
0 answers

Video For Linux 2 dequeuing is unbelieveably slow

What I do is: Open the camera by: query the capabilities set the format set the framerate request 4 buffers query all 4 buffers use mmap (I don't know anything about what this does) turn the streaming on queue all 4 buffers And then during every…
Gabe Rundlett
  • 87
  • 8
0
votes
2 answers

getting multiple v4l errors using opencv with multiple webcams on a raspberry to shoot a timelapse

I'm posting this because i was already searching the web trying to find some explenation for the errors caused but didn't find any. So I'm trying to shoot a timelapse of a growing plant from 4 different angles. I have 4 webcams (Logitech B525)…
eALduderino
  • 1
  • 3
0
votes
0 answers

OpenCV camera (using python) w/TX1 works with sudo, but not without

I am trying to access a camera (external: leopard imaging mipi) with opencv on TX1 using the following script (tx1_mipi.py). I am able to access it when I run "sudo python tx1_mipi.py". (It does gives an error "VIDEOIO ERROR: V4L: appsink: Unable to…
Priya Narayanan
  • 1,197
  • 2
  • 10
  • 16
0
votes
1 answer

VIDIOC_REQBUFS Error 12 when opening multiple v4l2 sources

I'm using an 8-channel PCI-based framegrabber on Nvidia TX1 dev kit. I'm using this driver along with it. I can play up to 3/4 v4l2 camera feeds comfortably using mplayer, streamer or VLC but I always get a memory allocation error when I start…
alasin
  • 172
  • 3
  • 15
0
votes
2 answers

MAC address of TBS6905 DVB-S2 Quad Tuner PCIe Card

I have TBS6905 DVB-S2 PCIe card and its configured in Ubuntu 14. And I have to find MAC address of all adapters because my application will do Blind Scan for all four adapters at the same time. And index of these adapters will change after…
Parbat
  • 1
  • 1
0
votes
1 answer

How to stop v4l2-ctl streaming?

Suppose I run v4l2-ctl --stream-mmap=3 --stream-to=/dev/null, how to stop recording without pressing Ctrl+C for interrupt, from another shell console for example?
Delgan
  • 18,571
  • 11
  • 90
  • 141
0
votes
1 answer

Choose yuy2 or MJPEG in V4L

I am implementing a Camera Preview application. I am using V4L and until now I basically use this code> https://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html In this example, or any other example I found for that matter, I could not find a…
BT9
  • 87
  • 1
  • 11
0
votes
1 answer

V4L2 preview with callback instead of polling-loop

I just started looking into V4L2 and all the samples I can find use loops to poll images from the camera. Is there a way to register a callback instead of looping? I can't figure out when to poll images and it does not seem like a good idea to just…
BT9
  • 87
  • 1
  • 11
0
votes
1 answer

Linux V4L driver - Polling camera input format

I am unfamiliar with Linux kernel development but I'm tasked with updating a kernel driver so that it will return a status code that can be read by an application. This will require that the driver poll the hardware a couple of times a second to…
Bryan C.
  • 347
  • 1
  • 12
0
votes
1 answer

Capture 1920x1080 video with OpenCV over Raspberry PI

Hardware: 1. Raspberry Pi 2 2. Raspberry Pi Camera Software: 1. OpenCV 2.4.11 2. Programming with C++ I've the following trivial code that capture video from camera and displays it within window. The frame size is always 640 x 480, trying to…
teach me
  • 453
  • 5
  • 20
0
votes
3 answers

v4l2 build error on Debian 8

I am installing video 4 linux following these steps, http://www.linuxtv.org/wiki/index.php/How_to_Obtain,_Build_and_Install_V4L-DVB_Device_Drivers but when build, following error appears. Debian 8 virtual machine. ... CC [M] …
Jaume
  • 3,672
  • 19
  • 60
  • 119
0
votes
1 answer

How to wait for frame and alarm signal

I have problem with a webcam. It can be a hardware one but i'm convinced it is no. With all apps I can see the stream but suddenly it freezes. Because of the following output from used app when the problem occurs: v4l: timeout (got SIGALRM),…
Cecylia
  • 349
  • 4
  • 12
0
votes
0 answers

Highgui V4L error when using MJPEG for OpenCV

I am running OpenCV on an ARM A9 processor. I am trying to use MJPEG so my C920 webcam runs a lot faster. The beginning of my program is as follows: VideoCapture cap(CV_CAP_ANY); cap.set(CV_CAP_PROP_FOURCC, CV_FOURCC('M', 'J', 'P',…
Stefan G.
  • 167
  • 7
0
votes
1 answer

Ubuntu Opencv Camera settings V4L2 error Exposure control not supported

I wrote a simple Opencv program in Ubuntu 12.04LTS that adjusts a webcam (Logitech C525) settings like brightness and exposure and such. It works fine in Windows 7, but in Linux it gives me this error $ ./adjust-camera init done opengl…
ChumbiChubaGo
  • 968
  • 2
  • 9
  • 15
1 2
3
4