UNABLE(1)

🌸 NAME 🌸

okay so bestie, welcome to the unable(1) page 💅 — the manual name is literally UNABLE, and it lives in User Commands. This whole page is about unable, which controls v4l2 loopback devices. No cap.

✨ SYNOPSIS ✨

v4l2loopback-ctl [OPTIONS]
v4l2loopback-ctl add [OPTIONS] [<outputdevice> [<capturedevice>]]
v4l2loopback-ctl delete <device>
v4l2loopback-ctl list [OPTIONS]
v4l2loopback-ctl query [OPTIONS] <device>
v4l2loopback-ctl set-fps <device> <fps>
v4l2loopback-ctl get-fps <device>
v4l2loopback-ctl set-caps <device> <caps>
v4l2loopback-ctl get-caps <device>
v4l2loopback-ctl set-timeout-image [OPTIONS] <device> <image>

🦋 DESCRIPTION 🦋

Managing v4l2 loopback devices is the whole vibe here. The normal way to call it is with a verb — stuff like add or delete — and that verb tells it what action to run. Every verb comes with its own options and arguments, iykyk.

💖 OPTIONS 💖

• -h, -?, --help — print this help and exit 🫶
• -v, --version — print version and exit ✨

🔥 VERBS AND THEIR ARGUMENTS 🔥

🎀 v4l2loopback-ctl add [OPTIONS] [<outputdevice> [<capturedevice>]]:

create/add a new loopback-device — iconic behavior, honestly.

• -b <num>, --buffers <num> — buffers to queue 🍓
• -h <h>, --max-height <h> — maximum allowed frame height
• -n <name>, --name <name> — pretty name for the device ✨
• -o <num>, --max-openers <num> — maximum allowed concurrent openers
• -v, --verbose — verbose mode (print properties of device after successfully creating it) 👀
• -w <w>, --max-width <w> — maximum allowed frame width
• -x <x>, --exclusive-caps <x> — whether to announce OUTPUT/CAPTURE capabilities exclusively
• --min-width <w> — minimum allowed frame width
• --min-height <w> — minimum allowed frame height
• -?, --help — print this help and exit
• <outputdevice> — if given, create a specific device (otherwise just create a free one). either specify a device name (e.g. '/dev/video1') or a device number ('1'). 🎀
• <capturedevice> — if given, use separate output & capture devices (otherwise they are the same). 💅

🦋 v4l2loopback-ctl delete <device>:

delete/remove an unused loopback device.

• <device> — can be given one more more times (to delete multiple devices at once). either specify a device name (e.g. '/dev/video1') or a device number ('1'). 🫶

🌈 v4l2loopback-ctl list [OPTIONS]:

list all available loopback-devices.

• -e, --escape — escape control-characters in (device) names
• -h, --help — print this help and exit

💜 v4l2loopback-ctl query [OPTIONS] <device>:

query information about a loopback device.

• -e, --escape — escape control-characters in (device) names
• -h, --help — print this help and exit
• <device> — can be given one more more times (to query multiple devices at once). either specify a device name (e.g. '/dev/video1') or a device number ('1'). 🔍

⭐ v4l2loopback-ctl set-fps <device> <fps>:

set the default framerate for a loopback device.

• <device> — either specify a device name (e.g. '/dev/video1') or a device number ('1').
• <fps> — frames per second, either as integer ('30') or fraction ('50/2'). 🎬

🧚 v4l2loopback-ctl get-fps <device>:

query the framerate of a loopback device.

👑 v4l2loopback-ctl set-caps <device> <caps>:

set format/dimension/framerate of a loopback device.

• <device> — either specify a device name (e.g. '/dev/video1') or a device number ('1').
• <caps> — format specification as '<fourcc>:<width>x<height>@<fps>' (e.g. 'UYVY:1024x768@60/1') unset the current caps with the special value 'any'. 🔥

🍓 v4l2loopback-ctl get-caps <device>:

get current format/dimension/framerate of a loopback device.

💀 v4l2loopback-ctl set-timeout-image [OPTIONS] <device> <image>:

set a fallback image to be used if a video producer does not send new frames in time.

• <flags> — any of the following flags may be present
• -h, --help — print this help and exit
• -t <timeout>, --timeout <timeout> — timeout (in ms) ⏳
• -v, --verbose — raise verbosity (print what is being done) 👀
• <device> — either specify a device name (e.g. '/dev/video1') or a device number ('1').
• <image> — image file 🖼️

🌈 REPORTING BUGS 🌈

• Issue tracker: https://github.com/umlaeute/v4l2loopback/issues
• Security Issue tracker: https://git.iem.at/zmoelnig/v4l2loopback/-/issues

and that’s the whole page, bestie 🫶 — this beauty is utils/v4l2loopback-ctl v0.15.4, dated August 2026, and the footer even hits you with unable to open control device ... 😭💀 periodt.