libv4l1

libv4l1 is a user-space library that provides compatibility for applications written to the Video4Linux version 1 (V4L1) API when interfacing with video devices on Linux. It implements a subset of the V4L1 interface in terms of the modern V4L2 kernel API, enabling legacy software to work with current drivers without modification.

The library operates as a translation layer: when a V4L1 application issues ioctls, reads, or memory-mapped I/O calls, libv4l1 translates them into corresponding V4L2 operations and buffers. This can allow older programs to capture video and perform basic control tasks using modern devices. However, libv4l1 does not emulate every aspect of the original V4L1 feature set, and some advanced capabilities may be unavailable or behave differently.

libv4l1 is distributed as part of certain Linux distributions alongside v4l-utils or as a standalone library. Applications link against -lv4l1 and rely on the runtime to mediate access to /dev/video* devices. The library is primarily intended for compatibility during migration from V4L1 to V4L2 and is increasingly considered deprecated in favor of direct V4L2 usage.

See also: Video4Linux, V4L2, libv4l2, LinuxTV, v4l-utils.