libv4l

libv4l is a free, open-source userspace library for Linux that provides access to Video4Linux (V4L) devices. It aims to simplify programming against the V4L API by offering compatibility wrappers and frame data conversion, enabling applications to work with a wide range of cameras and capture devices.

The library comprises components that offer compatibility across the V4L1 and V4L2 interfaces. It allows applications written for older V4L APIs to interact with modern devices and can present V4L2 devices in a way that aligns with the expectations of legacy software. In addition, a conversion module handles differences in pixel formats and color spaces, returning a common format to consumers.

libv4l is widely used by multimedia applications on Linux, including video capture tools and other software that relies on standard Linux device nodes such as /dev/video*. It is distributed with many Linux distributions and is commonly installed as a runtime library along with development headers for building against V4L compatibility layers.

Within the broader Linux media ecosystem, libv4l plays a coordinating role alongside kernel drivers for V4L devices and other userspace libraries. It helps bridge gaps between device capabilities and application expectations, particularly for formats and interfaces that differ across devices and kernel versions. Some setups also use supplementary libraries such as libv4lconvert, which performs image format conversion to formats widely supported by players and encoders.

See also: Video4Linux, v4l-utils, FFmpeg, GStreamer.