Questions tagged [v4l2]
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52
questions
0
votes
1answer
41 views
Trying to emulate a hardware camera with a stream from a raspberry pi/picam?
I have a raspberry pi and pi cam v2 connected to wifi. I am trying to stream the camera feed to a laptop over wifi, then make that stream appear as if it were a hardware camera on the laptop. I want ...
0
votes
1answer
76 views
Can't play video file to virtual camera and then webcam to virtual camera v4l2
When I try to play a video to a virtual camera it works
but when I try to play webcam to virtual camera it doesn't do anything.
What I do:
Playing video to virtual camera:
ffmpeg -re -i "yt.mkv&...
0
votes
0answers
28 views
How to re-encode or compress a v4l2 virtual video device to another virtual device?
what I'm trying to do is to compress video from my webcam so that it's accessible from another v4l2 virtual device (or an alternative medium if necessary) with a bitrate around 2000kbps.
Currently ...
0
votes
1answer
114 views
Howto redirect cheese webcam effect to new video device
I am on ubuntu 20.04, but v4l2 package is not working: so I installed it from here
git clone git@github.com:umlaeute/v4l2loopback
make
sudo insmod v4l2loopback.ko exclusive_caps=1 video_nr=1 ...
1
vote
1answer
561 views
MJPEG stream from webcam not working
I have 5 HD Webcams (Creative Live Cam Sync 1080p) and want to stream the pictures with https://github.com/jacksonliam/mjpg-streamer on Debian Buster 4.19.0-11-amd64.
All of them support MJPG, as you ...
0
votes
1answer
428 views
V4L2 Loopback: VLC can use it, but a web browser can't
I have a bunch of USB 3 capture devices feeding OBS, and V4L2 Loopback to provide OBS's output as another video input. (/dev/video99) I want to use that output in an online meeting, but neither ...
1
vote
0answers
24 views
FFmpeg/FFplay sometimes goes to sleep waiting on IO when webcam is unplugged
I made a webcam viewer out of a Raspberry Pi with Raspbian, FFmpeg/FFplay, and v4l2. I have a udev rule that automatically starts an FFmpeg stream and brings up FFplay to view it when my webcam is ...
0
votes
1answer
20 views
Simultaneusly connecting several webcams
I have 4 webcams, plugged into a USB hub, that I would like to use with my computer. I can find out which devices are recognized by the computer with v4l2-ctl --list-devices. When I plug the entire ...
0
votes
1answer
106 views
Rename Devices in V4L2?
I have 4 identical HDMI -> USB 3 capture devices, meant to feed a live broadcast. That works just fine. After some one-time trial-and-error on the initial install, the broadcast production ...
0
votes
1answer
97 views
How do I stream JPGs to v4l2loopback with ffmpeg?
I'm trying to use ffmpeg to stream images into v4l2loopback, but it seems like only pngs work. Here's the command that I am using, where <image> is the path to an image, and /dev/video63 is a ...
0
votes
0answers
239 views
FFmpeg: synchronize streams from two webcams
Making an MP4 file with two video streams, each from a different webcam, like this:
ffmpeg -f v4l2 -thread_queue_size 32 -video_size 1920x1080 -input_format mjpeg -i /dev/video6 \
-f v4l2 -...
0
votes
1answer
789 views
Stream linux destop as fake webcam to virtuabox windows guest
I would like to capture (a part of) my linux desktop (ubuntu 20.04), stream it as a webcam to a windows 10 guest VM running in Virtualbox.
I found Using desktop as fake webcam on linux which got me ...
0
votes
1answer
235 views
Green tinted flickering screen with FFmpeg + v4l2loopback-dkms
I have a Raspberry PI 4 with a Raspberry 7" touch screen, where buster is installed with Ffmpeg, Gstreamer, and v4l2loopback-dkms.
To that I have attached a USB video grabber dongle, where I have ...
2
votes
0answers
623 views
FFmpeg output sent to v4l2loopback video device won't be read by guvcview
I set a dummy camera /dev/video1 with v4l2loopback module.
I can read the stream with ffplay, vlc or even zoom of this camera when I send to it contentwith ffmpeg:
ffmpeg -re -i input-file.mp4 -f v4l2 ...
0
votes
1answer
158 views
virtual webcam from dvcam input on firewire - linux
I'd like to use my dvcam as a webcam on linux (ubuntu 18.04). It works happily under windows showing up as a video source.. but on linux not so easy.
It shows up on /dev/fw0 & fw1 as 720x576 ...
0
votes
1answer
575 views
Realtime overlay png image (with tansparency) over webcam output to feed to v4L2 loopback virtual video camera
I've been struggling with this for a few days and just can't get the final part of the FFmpeg command right. I'd be very grateful for any help please. I have studied similar questions and answers on ...
1
vote
0answers
1k views
“Non-monotonous DTS in output stream” when capturing video with ffmpeg
I'm trying to capture VHS video on Linux using a new USB capture device and FFMPEG.
I'm able to successfully capture either only audio (using Alsa), or only video (using v4l2) but when I try to do ...
1
vote
2answers
1k views
Linux USB video capture issues
I purchased the Hauppauge USB-Live 2 capture device because several recent Amazon reviews suggest it should work with modern Linux kernels.
When I plug it into my Raspberry Pi 4 running the latest ...
1
vote
0answers
64 views
Synchronize multiple realtime inputs
I'm trying to record a video+audio using ffmpeg from 3 sources: x11grab (desktop), v4l2 (webcam) and alsa (microphone). I'm using this script:
#!/bin/bash
set -x
out=$1
rm -vf $out
rate=25
cam_size=...
0
votes
1answer
225 views
Merge x11grab with v4l2 into single output file
I'm trying to record a video using ffmpeg from two inputs: webcam (v4l2) and desktop (x11grab). I checked that both inputs are working fine:
ffmpeg \
-f x11grab -s 1920x1080 -r 25 -i :0.0 \
-...
1
vote
1answer
1k views
gstreamer using h264 encoding with small video size
I need to record a video using my usb webcam in my linux based pc. I found gstreamer with h264 encoding for lower the cpu percentage.
But i am new to gstreamer so i had errors when running some ...
0
votes
1answer
458 views
Piping mp4 video file to v4l2 devices lowers the frame rate in ffmpeg
I'm trying to play a 10fps video file on multiple v4l2 loopback devices.
Although the following command outputs the video on the video devices, it does not maintain the framerate. The framerate (and ...
0
votes
1answer
235 views
Gstreaming - two web cams over tcp
I'm trying to stream two web cams on a single gstreaming command, I'm able to start a single camera with :
gst-launch-1.0 v4l2src device=/dev/video0 ! videoconvert ! videoscale ! video/x-raw,width=...
1
vote
0answers
1k views
V4L2 doesn't use a lower advertised frame rate
I'm capturing images on Linux (Pi 3B+, Stretch lite). The camera reports that it's capable of delivering images at 30 fps or 60 fps. Here's the output from v4l2-ctl
v4l2-ctl --list-formats-ext
ioctl: ...
1
vote
0answers
875 views
How to inform vlc for sample rate change from device in linux
I'm working in FPGA device, which can provide raw video and pcm data. I'm using v4l2 and alsa framework for video and audio respectively. Audio flow path is using ALSA framework and video flow path is ...
3
votes
0answers
1k views
What is the right ffmpeg output format for playing a video to webcam using v4l2-loopback in linux? [duplicate]
please can someone show me the new syntax for sending videos to webcam using ffmpeg and v4l2loopback?
It used to work perfectly until I updated and upgraded recently
the previous syntax i use is:
...
5
votes
1answer
19k views
What is the right ffmpeg output format for a v4l2-loopback device?
Following the guide in this question I did:
$ sudo modprobe v4l2loopback
$ ffmpeg -f x11grab -r 15 -s 1280x720 -i :0.0+0,0 -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0
The device ...
asked Jun 13 '18 at 12:38
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3
votes
0answers
3k views
ffmpeg stream video file to fake webcam
I'm trying to set up ffmpeg to forward video stream from file to dummy video device created by v4l2loopback
My command looks like following:
ffmpeg -re -i video.mp4 -c:v rawvideo -pix_fmt yuv420p -f ...
0
votes
1answer
94 views
Identify kernel module for analogue video capture card Multimedia video controller: Adaptec (formerly DPT) Device 9065
I'm trying to identify a kernel module to make an analogue video capture card work on video4linux.
lspci:
Multimedia video controller: Adaptec (formerly DPT) Device 9065
02:04.0 Class 0400: Device ...
1
vote
0answers
240 views
EM2860 based video converter captures corrupted frames (how to debug?)
I designed my own analog video to USB converter. This converter is based on the TI TVP5150AM and the Empia EM2860. Shortly the converter works as shown in the diagram below.
+---------+ ITU-...
0
votes
1answer
2k views
Compile Linux V4L-DVB media_build for a specific kernel (not the running one)
Is it possible to compile the LinuxTV.org V4L-DVB media_build for a kernel source contained in a specific path, instead of the running one (i.e. a different version)?
I have the kernel sources and in ...
1
vote
2answers
5k views
v4l2 Identifying /dev/video* via lsusb
I'm writing a script that must use a particular camera plugged in to my system.
$ lsusb|grep C930e
Bus 001 Device 011: ID 046d:0843 Logitech, Inc. Webcam C930e
How can one programatically discover ...
1
vote
1answer
6k views
FFmpeg build with V4L2
I want to use ffmpeg to access my webcam. I tried:
ffmpeg -f v4l2 -i /dev/video0 output.mp4
but I am getting an error:
Unknown input format: 'v4l2'
Similarly with video4linux2 instead of v4l2. I ...
0
votes
1answer
1k views
No such input format: MJPEG
I want to convert my camera pixels format from YUYV to MJPEG. I tried to use v4l-utils but when i used this commend in terminal:
ffmpeg -f video4linux2 -pixel_format MJPEG -i /dev/video0
but when I ...
3
votes
0answers
7k views
How to know which framerate should I use to capture webcam with ffmpeg?
I'm capturing video from my webcam with the following command:
ffmpeg -r 30 -f v4l2 -video_size 160x120 -i /dev/video0 output.avi
The -r option indicate the framerate I want. However, it's not that ...
10
votes
3answers
10k views
Can I use my DSLR as webcam through gphoto2 + v4l2loopback?
So, what i'm trying to do may be a little complicated, by i'm finding my way.
Let me explain the basics:
1 - I have an DSLR camera and i want to use it as webcam (but v4l2 can't make a /dev/videoX ...
0
votes
1answer
537 views
Video for Linux (V4L) generator driver
I would like to experiment with tvheadend but prior to investing in an actual capture card I was wondering if V4L supports a "generate" capture "card" that can just offer video stream of an image or ...
2
votes
1answer
3k views
Alternatives to Video4Linux2 for grabbing from webcam (Using FFmpeg)
I'm getting (two alternating) errors following this guide for streaming from a Raspberry Pi. Are there any other grabbers besides V4L2 that I can use with ffmpeg?
Or are there any other streaming ...
2
votes
0answers
1k views
Analog Tv Tuner drivers for ubuntu
I was searching for the Analog usb (stick) tv tuner card for Ubuntu, but I have not found single such tv tuner card with ubuntu drivers available. I tried to search for the open source tv tuner ...
1
vote
2answers
4k views
v4l2 issues with webcam encoded to H.264
I am trying to send a H.264 webcam video feed over wifi to another computer using gstreamer. I am using this tutorial as a guide. I am using a Creative Live! Cam Connect HD as my webcam. The website ...
2
votes
1answer
3k views
No permission to access webcam on linux
I am using a raspberry pi with raspbian to capture webcam shots and upload them to a web server. However, when I rebooted just now I no longer have access to the webcam. I have no idea why this ...
2
votes
2answers
3k views
How Video4Linux and ALSA work with Codecs
My understanding is that a codec is both a decoder and a specification for decoding. So some group writes a codec which explains how to decode from their format back into the raw bitstream, and they ...
2
votes
1answer
356 views
V4L2 and ALSA: Kernel SPI or User API?
I'm trying to understand what Video for linux and ALSA are (exactly), and I can't discern whether they're APIs for Linux application to use (the userspace) or if they are backend services that are ...
19
votes
2answers
50k views
ffmpeg open webcam using YUYV but i want MJPEG
I need ffmpeg to open webcam (Logitech C910) in MJPEG mode, because the webcam can give ~24 fps using the MJPEG "protocol" and only ~10 fps using the YUYV. Can I choose between them using ...
0
votes
1answer
2k views
Devices renamed with udev not working, original device node still there
I'm trying to rename certain video devices using udev. Here's a rule (broken down for readability):
ACTION=="add", SUBSYSTEM=="usb", ATTR{busnum}=="1",
ATTR{devpath}=="2", ATTR{idVendor}=="05e1", ...
0
votes
2answers
95 views
Camera's in Linux switch filename on boot
I've got a few camera's for use in Zoneminder. But they tend to switch places upon boot.
One tiem camera a will get /dev/video0, the other time it will be /dev/video1.
Is there a way to set these ...
4
votes
2answers
7k views
Linux (v4l) webcam - make settings “stick”
My Logitech camera (C300) is properly detected and present at /dev/video0. However, by default the image has contrast and saturation set to maximum, which significantly degrades the image quality.
I ...
4
votes
1answer
2k views
Why can’t two programs access my webcam simultaneously?
I first launch cheese and my webcam turns on. I then run vlc to grab the output of /dev/video0 but it fails with:
[0x7f3ea40012e8] v4l2 demux error: cannot set input 0: Device or resource busy
[...
0
votes
1answer
1k views
v4l - capture and watch at the same time
Capturing v4l and line-in audio using mencoder works very well, but I would like to record real-time game play video from consoles plugged into the video card.
I've used xawtv for this (Works quite ...
4
votes
1answer
3k views
Poor image quality and high CPU usage while streaming in high resolution using webcam and VLC in Linux
I'm trying to do some some streaming with a webcam, but so far the results are not good: everything I stream in 320x240 looks good, but as soon as I choose a higher resolution, the image quality gets ...
