今天发现一个可用于编写v4l2 camera应用程序的库libv4l

今天发现一个可用于编写v4l2 camera应用程序的库libv4l,里面除有常用的v4l2 ioctl调用的封装API外，还有yuv到rgb转换、rgb到yuv转换和jpeg decoder API。下载地址是：http://people.atrpms.net/~hdegoede/libv4l-0.5.9.tar.gz 。

以下是README的英文介绍：

Introduction
------------

libv4l is a collection of libraries which adds a thin abstraction layer on
top of video4linux2 devices. The purpose of this (thin) layer is to make it
easy for application writers to support a wide variety of devices without
having to write seperate code for different devices in the same class.

All libv4l components are licensed under the GNU Lesser General Public
License version 2 or (at your option) any later version.

libv4l consists of 3 different libraries:


libv4lconvert
-------------

libv4lconvert offers functions to convert from any (known) pixelformat
to V4l2_PIX_FMT_BGR24 or V4l2_PIX_FMT_YUV420.

Currently the following source formats are supported:
jpeg, mjpeg, bayer (all 4 variants: bggr, rggb, gbrg, grbg),
spca501 (chip specific yuv 420 with interlaced components),
spca561 (chip specific compressed gbrg bayer)
For more details on the v4lconvert_ functions see libv4lconvert.h .


libv4l1
-------

This offers functions like v4l1_open, v4l1_ioctl, etc. which can by used to
quickly make v4l1 applications work with v4l2 devices. These functions work
exactly like the normal open/close/etc, except that libv4l1 does full emulation
of the v4l1 api on top of v4l2 drivers, in case of v4l1 drivers it will just
pass calls through. For more details on the v4l1_ functions see libv4l1.h .


libv4l2
-------

This offers functions like v4l2_open, v4l2_ioctl, etc. which can by used to
quickly make v4l2 applications work with v4l2 devices with weird formats.
libv4l2 mostly passes calls directly through to the v4l2 driver. When the
app does a TRY_FMT / S_FMT with a not supported format libv4l2 will