V4L2 is a thorough overhaul of the API with respect to Video for Linux, and not backward compatible with the original API, so drivers already written for Video for Linux will have to be ported to work with V4L2.
Applications should also be ported to make the best use of V4L2, but there is a backward compatibility layer built in to the V4L2 high level driver that translates the old ioctl commands, so many applications written for the original API will still work with V4L2 drivers.
On this page you will find general information about V4L2, and V4L2
resources,
including documentation and source code, and links to drivers and
applications
that have been written for or ported to V4L2.
At the People & Projects
page.
This is a list of people who are contributing to V4L2 or doing
V4L2-related work, and the projects they are working on. These include
specifications, drivers, libraries, and applications.
V4L2 can be used on 2.2.x kernels or 2.4.x kernels. Video for Linux is embodied in the videodev.h header file and the videodev or videodevX kernel module. The module that comes with the kernel only supports the original API. To use V4L2 drivers you must get a replacement videodev.h and videodev module that includes V4L2.
The videodev package below works only with 2.2.x kernels, and supports only V4L2 drivers.
A new version, videodevX, that works in 2.2.x and 2.4.x and
supports
both V4L2 and v4l drivers is now available.
| Video for Linux Two Devices | 1999-09-12 |
| Video Capture API Specification | 1999-09-14 |
| Data Services Interface (VBI) Specification | 2000-11-23 |
| Codec API Specification | 1999-09-13 |
| Effects API Specification | 1999-09-19 |
| Video Output Device API Specification | 1999-09-19 |
| Standard Image Formats | 2003-06-26 |
| Driver Writer's Guide | 1999-12-23 |
| All API documents in a gzip'ed tar file: v4l2api.tgz | 78 KB |
Change Log for the API and Source Code
For instructions on installing V4L2 see the readme file in the V4L2 source archive. You will need to configure your kernel to include Video for Linux as a module, but disable all the v4l drivers since they will not compile after the original v4l header file has been replaced with the new header file.
The v4l2samp.tgz file includes a sample device drivers which use no hardware, so you can start writing or porting applications to V4L2 even if you don't have V4L2-supported hardware yet. So far video capture and video output sample drivers are included. More information is in the readme file included in the archive.
Notice: On Sep 21, 1999 I introduced
some changes into the API that are not backward compatible.
| V4L2 source code for kernel 2.2.x. Unpack in /usr/src/linux. | videodev20010302.tgz | 2001-03-02 (24KB) |
| Sample drivers for kernel 2.2.x (v4l2cap.c, v4l2out.c) | v4l2samp20000627.tgz | 2000-06-27 (32KB) |
| FTP site for videodev, kernel 2.2.x. Current and previous versions. | kernel2.2/videodev | |
| FTP site for sample drivers. | kernel2.2/v4l2samp |
See the drivers/char/v4l2readme.txt file for details.
When you unpack videodev*.tgz in /usr/src/linux, it will overwrite include/linux/videodev.h and drivers/char/videodev.c. You may want to keep backup copies of these files in case you decide to go back to v4l.
Videodev.c and videodev.h are covered by the GPL. The sample drivers
are
public domain and have no copying or derived-work restrictions of any
kind.
For 2.4.x, the videodev module is replaced by videodevX, originally created by Justin Schoeman. The videodevX module supports both v4l and V4L2 drivers simultaneously. VideodevX should work on 2.2.x kernels also.
Download the videodevX package, and unpack it. It is not meant to unpacked in the kernel source tree, unpack it in some other convenient place. It will create a directory called videodevX with the videodevX source files and a Makefile.
Before installing videodevX you will need to enable Video for Linux
in your kernel config as a module, and rebuild your kernel modules if
necessary. Then install videodevX. See below.
| Latest V4L2 source code for kernel 2.4.x. | videodevX-20030626.tgz | 2003-06-26 (36KB) |
| Latest sample capture driver for 2.4.x. | v4l2samp-20020330.tgz | 2002-03-30 (20KB) |
| FTP site for videodevX, kernel 2.4.x. | kernel2.4/videodevX | |
| FTP site for sample drivers. | kernel2.4/v4l2samp |
VideodevX.c and videodev.h are covered by the GPL.
There is a sample capture program, xcaptest.c, which exercises the
capture
functions of a V4L2 driver, and a video control panel program,
vidpanel.c,
that exercises the brightness, contrast, etc. controls on a V4L2
device.
These require X Windows. In addition, command line programs vcat and
vctrl
programs are for capturing frames, and setting device parameters are
included. All applications work with the sample capture driver.
| Sample applications (xcaptest, vidpanel, vcat, vctrl). Includes a Makefile | apps20020317.tgz | 2002-03-17 (10KB) |
| FTP site for sample applications. | apps |
The sample applications are public domain (not GPL), and have no
copying
or derived-work restrictions.
An excellent source of help for general Video for Linux issues is the video4linux mail list.
If you would like to contribute to the V4L2 project, or have any questions about the API or software supporting it, send me an email. Of course, I will be happy to answer any questions about V4L2 or provide advice or assistance with writing V4L2 drivers or applications.
If you have suggestions or patches for V4L2 source code send them to
me
at bdirks@pacbell.net
. If sending patches, I would ask that you please send patches as
(gzip'ed) attachments because it has been my experience that 'patch'
almost always rejects
patches emailed in the body of a letter due to either tabs converted to
spaces
or wrapping of long lines.