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Questions tagged [v4l2]

v4l2 (video for Linux 2) is a video capture interface for a variety of video capture devices tested to be fully compatible with Linux. v4l2 is commonly used by programs and frameworks such as Ekiga, gstreamer, Mplayer, Skype, and VLC media player.

A good place to start understanding the V4L2 framework is the following series of articles on lwn.net.

Part 1: The Video4Linux2 API
Part 2: registration and open()
Part 3: Basic ioctl() handling
Part 4: Inputs and Outputs
Part 5a: Colors and formats
Part 5b: Format negotiation
Part 6a: Basic frame I/O
Part 6b: Streaming I/O
Part 7: Controls

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Opencv Vs FFmpeg performance comparision for web cam feed recording

I'm working on my academic project in which I've to record a video from the webcam. In my google search, I've found that FFmpeg uses pipelining to record the video from the camera while OpenCV, AVbin use ctypes. I don't know the pros and cons of…
Chakri
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Which video library is OpenCV using under the hood on linux?

I'm writing a simple software to capture and record webcam images to a compressed video file. I'm using OpenCV "VideoCapture read(frame)" and "VideoWriter write(frame)" in a C++ software. I'm on Ubuntu 14.04 LTS operating system. I would like to…
ssinfod
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ERROR opening V4L interface: Operation not permitted

I compiled mjpg-streamer in my raspberry pi, but when I run the below command, it occured an eeror shown in the title. Details are below: root@raspberrypi:/home/pi/mjpg-streamer-code-182/mjpg-streamer# /usr/local/bin/mjpg_streamer -i…
Zezhou Li
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Cross Compiling v4l2-ctl for Android

I've got a usb camera working on android (via Android On-The-Go), and I'm looking to change the exposure of the camera. I've been able to get this to work by using v4l2-ctl on a linux machine, and I'm hoping to do the same on my Android device. The…
theicfire
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How to access external usb camera on unrooted android devices

I want to access extern usb cameras via v4l on android. I tried SimpleWebCam. After some slight modifications of the original source codes, i achieved to make it work on a rooted android device. However, on unrooted devices, it keeps complaining…
Yang Kui
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OpenCV capture YUYV from camera without RGB conversion

I trying to use openCV/c++ to capture the left and right image from a LI-USB30_V024 stereo camera without automatically converting it to RGB. The camera outputs images in YUYV format. I have tried using videoCapture.set(CV_CAP_PROP_CONVERT_RGB,…
titch
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OpenCV VideoCapture / V4L2 latency when grabbing a new webcam image

For a computer vision project that I am working on I need to grab images using a Logitech C920 webcam. I am using OpenCV's VideoCapture to do that, but the problem that I am facing is that the image that I take at a certain moment does not show the…
Mihai Morariu
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V4L2 driver corrupts buffers for 4 USB cameras on Android OMAP5432

I have OMAP5432 EVM running Android 4.2 with 4 USB connected Logitech C270 cameras. I use V4L2 driver from NDK C-code to open and stream from cameras in MJPEG mode. Everything works fine except right after power cycling cameras. After power cycling…
Leo
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dma buf sharing between multiple processes

I am trying to understand the dma buf framework in linux kernel and going through this article http://lwn.net/Articles/489703/ which says Userspace entity requests for a file-descriptor (fd) which is a handle to the anonymous file associated…
Ravi Chandra
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How to get Gstreamer1.0 working with v4l2 raspicam driver

For the last 4 days I'm trying to get gstreamer1.0 working with v4l2 driver for Raspberry Pi camera, but with no success. I'm running the latest Raspbian image (from 19.9.2014.), with raspicam enabled. Raspicam bcm2835_v4l2 driver was started with…
Bero_zg
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Official V4L2 Driver for raspberry pi, how do I add lrt flags to a makefile?

I am creating a small python application that uses v4l on the raspberry pi. After hours of troubleshooting I'm close to installing it. I just need to compile the Official V4L2 Driver. I'm following this tutorial…
Rob Dickson
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V4L2 video capture on android

I'm trying to run the video capture example code here on a Samsung Galaxy S3. At first I encountered several errors in many of the VIDIOC operations (for example S_FMT or STREAMON) which I could solve by: Looking at kmsg and tracing the kernel…
sundie
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Where I can find example in using v4l2 codec driver

in Raspberry-Pi code, there is a s5p-jpeg codec driver. drivers/media/platform/s5p-jpeg/jpeg-core.c Can sombody please tell me where I can find an example of how to use it? Or any other v4l2 codec driver? I have googled for it, but I cannot find…
michael
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Undefine reference for libraries, so How could I find the right path?

I am trying to compile a v4l2 example in Ubuntu but I am getting the following error: guilherme@notedev01:~/Downloads/V4l2_samples-0.4.1$ make gcc -O2 -L/usr/include -lX11 -lXext -o viewer viewer.c /tmp/ccUjnjWQ.o: In function…
Guilherme Longo
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Video stream capture and frame rate control

I'm currently developing a video streaming software using VP8 and V4L2 but I'm struggling with the key concepts of frame rating. I have a basic working implementation that fetches frames in a loop, encodes it and sends it over RTP (as fast as it…
3XX0
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