Questions tagged [v4l]
Video4Linux is the linux kernel video capture subsystem, with a set of userland utilities.
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Custom Linux No /dev/video0 for i2c camera decoder
I am trying to use tw9990 connected to a ATSAMA5D29 to play a camera feed. I have a custom board where the digital data lines are going to the ISC lines of the processor. I have an embedded linux ...
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How do you configure a V4L2 device when V4L2 software cannot read a V4L2 stream directly, because they give IO errors?
I'm trying to capture video from an Elikliv UVC microscope in Linux.
We can do direct frame-by-frame capture using this command:
v4l2-ctl --device /dev/video0 --stream-mmap --stream-to=stream.mjpg
......
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How to get proper ffplay output with UVC camera?
My end goal is to use a UVC webcam with esp32 or Raspberry PI. I was hoping to learn while doing some fun projects.
I have an old UVC webcam (Creative model ct6840) but I can't seem to get it to work ...
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How can I persist the modified V4L2 (Guvcview) profile of a webcam?
I have a USB web camera that gives suboptimal results when I plug it in (Linux seems to apply its own V4L2 settings to it that it thinks are best, they are not). Mainly, it operates at a low FPS. But ...
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Unable to create device file of v4l2 framework
Cannot create /dev/video0 when I try to probing ov7670 driver in Linux run on Zedboard. The kernel version I'm using is 5.4 , I use Petalinux version 2021.1 to build Linux project and also enable the ...
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Webcam's power line frequency setting does not take effect if a new application that uses it is open
I am living in Europe and I have bought a Logitech C920 webcam whose power line frequency setting should be changed to 50Hz in order to avoid flickering. I did it using the following instruction:
/usr/...
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V4L2: Why image taken with shortest exposure-time looks way too brighter than auto-exposure mode?
When capturing image using the default auto-exposure-mode:
$ v4l2-ctl -d0 --set-fmt-video=width=width,height=height,pixelformat=MJPG --stream-mmap --stream-to=auto_expo.jpg --stream-count=1
auto_expo....
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How to make sure images captured by FFMPEG from USB is lossless?
I'm to capturing 10 images from camera. Like so:
ffmpeg -hide_banner -loglevel error -f video4linux2 -i /dev/video0 -vframes 10 -video_size 640x480 test%3d.jpg
Since JPG is lossly, at I need to ...
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Why would USB video be dropping frames in Realtime Linux?
We have a problem of losing about one frame every 60 seconds or so with four USB cameras hooked up to Ubuntu 20.04 with the Realtime Linux patches applied. From the user code ioctl(VIDIOC_DQBUF) call ...
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How to know the V4L2 camera's exposure time in ms?
with v4l2-ctl, one can know camera-parameters with following:
$ v4l2-ctl -d2 --list-ctrls
brightness 0x00980900 (int) : min=0 max=255 step=1 default=128 value=128
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v4l-utils for CentOS Stream 8?
I have problems with webcam and I need v4l-utils package. As per this page:
https://centos.pkgs.org/7/centos-x86_64/v4l-utils-0.9.5-4.el7.x86_64.rpm.html
It was availbel in CentOS 7 official repos. ...
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v4l2loopback: Virtual camera exists, but doesn't show up in Zoom, and doesn't work in Cheese
I have successfully set up the virtual camera in OBS:
sudo apt install obs-studio v4l2loopback-dkms
sudo usermod -aG video myuser
The following versions are installed:
v4l2loopback-dkms 0.12.5-1
obs-...
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Can't access IR video stream on mini camera
I bought a "IR capable" camera (https://er-estavel.com/product/1080p-hd-mini-kamera) but I can't get the IR part to work on Linux (current Archlinux).
v4l2-ctl --list-devices gets me:
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How to force v4l2 settings
I discovered that my webcam exposes a control called "LED1_mode". By setting it to zero, it is possible to turn off the status LED while the camera input is still active. Is there a way ...
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v4l2loopback devices not showing in applications
I have been successfully using v4l2loopback, with v4l2sink in OBS, to "send" my obs preview panel output to Zoom. The v4l2loopback devices have recently stopped showing in Zoom, Firefox &...
