From 44f2350b452580cafdb31157cfb54cf0ad0ff620 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Mon, 13 Apr 2020 21:23:42 +0200 Subject: [PATCH] Document V4L2 output. --- index.rst | 1 + v4l2.rst | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+) create mode 100644 v4l2.rst diff --git a/index.rst b/index.rst index 463d9f5..d543850 100644 --- a/index.rst +++ b/index.rst @@ -17,6 +17,7 @@ Contents: analyzer streaming hdmisdi + v4l2 theme video html diff --git a/v4l2.rst b/v4l2.rst new file mode 100644 index 0000000..8adde62 --- /dev/null +++ b/v4l2.rst @@ -0,0 +1,43 @@ +V4L2 output +=========== + +Since Nageru 1.9.3, Nageru has had (in addition to the regular +:doc:`hdmisdi`) support for output to Linux' Video4Linux API +(also known as V4L2, or just V4L). This is intended for one +specific purpose, namely using Nageru as a camera/mixer for +input to a video conference, such at Jitsi, Google Meet or +similar—it may not be all that suitable for an actual +output, since it does not carry audio (and does not synchronize +to any V4L clock). + +To use it as an input, you will first need to install +`v4l2loopback `_, +which turns V4L outputs into V4L inputs. If you are on +Debian or Ubuntu, the following should suffice to install:: + + sudo apt install v4l2loopback-dkms + +You will also need to load and configure the module, +using a command line such as:: + + sudo modprobe v4l2loopback video_nr=2 card_label='Nageru loopback' max_width=1280 max_height=720 exclusive_caps=1 + +The *exclusive_caps=1* parameter is so that once you start +outputting, the virtual card will appear only as an input +card to other V4L clients; in particular, Google Chrome +needs this, or the card will not show up. However, this means +that you will need to start Nageru output *before* trying to +use it in the browser. + +Finally, you can start Nageru as usual with the *--v4l-output* +flag, outputting to the device you just created:: + + nageru --v4l-output /dev/video2 + +Nageru should then show up as a device in your browser +or videoconferencing client. + +V4L output is in addition to any other output you may have +(whether stream output, :doc:`hdmisdi`, or both), and can +only be configured from the command line. It does not control +the master clock, is always 4:2:0; and does not include audio. -- 2.39.2