Extracted from libv4l-0.5.9/debian/control:
===========================================
libv4l-0 - Collection of video4linux support libraries
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 separate code for different devices in the same class. libv4l
consists of 3 different libraries: libv4lconvert, libv4l1 and libv4l2.
libv4lconvert offers functions to convert from any (known) pixelformat
to BGR24, RGB24, YUV420 and YVU420.
libv4l1 offers the (deprecated) v4l1 API on top of v4l2 devices, independent
of the drivers for those devices supporting v4l1 compatibility (which many
v4l2 drivers do not).
libv4l2 offers the v4l2 API on top of v4l2 devices, while adding for the
application transparent libv4lconvert conversion where necessary.
This package contains the shared libraries.
libv4l-dev - Collection of video4linux support libraries (development files)
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 separate code for different devices in the same class. libv4l
consists of 3 different libraries: libv4lconvert, libv4l1 and libv4l2.
libv4lconvert offers functions to convert from any (known) pixelformat
to BGR24, RGB24, YUV420 and YVU420.
libv4l1 offers the (deprecated) v4l1 API on top of v4l2 devices, independent
of the drivers for those devices supporting v4l1 compatibility (which many
v4l2 drivers do not).
libv4l2 offers the v4l2 API on top of v4l2 devices, while adding for the
application transparent libv4lconvert conversion where necessary.
This package contains development files (headers and static libraries).
lib32v4l-0 - Collection of video4linux support libraries (32 bits)
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 separate code for different devices in the same class. libv4l
consists of 3 different libraries: libv4lconvert, libv4l1 and libv4l2.
libv4lconvert offers functions to convert from any (known) pixelformat
to BGR24, RGB24, YUV420 and YVU420.
libv4l1 offers the (deprecated) v4l1 API on top of v4l2 devices, independent
of the drivers for those devices supporting v4l1 compatibility (which many
v4l2 drivers do not).
libv4l2 offers the v4l2 API on top of v4l2 devices, while adding for the
application transparent libv4lconvert conversion where necessary.
This package contains the 32 bits version of the shared libraries.
lib32v4l-dev - Collection of video4linux support libraries (32 bits development files)
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 separate code for different devices in the same class. libv4l
consists of 3 different libraries: libv4lconvert, libv4l1 and libv4l2.
libv4lconvert offers functions to convert from any (known) pixelformat
to BGR24, RGB24, YUV420 and YVU420.
libv4l1 offers the (deprecated) v4l1 API on top of v4l2 devices, independent
of the drivers for those devices supporting v4l1 compatibility (which many
v4l2 drivers do not).
libv4l2 offers the v4l2 API on top of v4l2 devices, while adding for the
application transparent libv4lconvert conversion where necessary.
This package contains the 32 bits version of the development files (headers
and static libraries).
Extracted from libv4l-0.5.9/debian/changelog:
=============================================
libv4l (0.5.9-1) unstable; urgency=low
* New Upstream Version
* Changed maintainers email address
* Bumped standards to version 3.8.1 (no changes needed)
-- Gregor Jasny <gjasny@NOSPAM> Fri, 13 Mar 2009 20:22:46 +0100
libv4l (0.5.8-1) unstable; urgency=low
[ Gregor Jasny ]
* New Upstream Version
[ Loic Minier ]
* Drop Section: libs from binary packages and rely on the Source's Section,
per lintian.
* Expand descriptions slightly for consistency; thanks lintian again.
-- Gregor Jasny <gjasny@NOSPAM> Sun, 11 Jan 2009 15:32:37 +0100
libv4l-0.5.9/debian/copyright:
==============================
This package was debianized by Gregor Jasny <gjasny@NOSPAM> on
Sun, 27 Jul 2008 11:01:46 +0200.
It was downloaded from http://people.atrpms.net/~hdegoede/
Upstream Author:
Hans de Goede <j.w.r.degoede@NOSPAM>
Copyright:
Copyright (C) 2008 Hans de Goede
License:
This package is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This package is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this package; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
On Debian systems, the complete text of the GNU Lesser General
Public License can be found in `/usr/share/common-licenses/LGPL'.
The Debian packaging is (C) 2008, Gregor Jasny <gjasny@NOSPAM> and
is licensed under the GPL, see `/usr/share/common-licenses/GPL'.
Bayer pattern decoding functions
* Written by Damien Douxchamps and Frederic Devernay
PAC207 decoder
* Bertrik.Sikken. Thomas Kaiser (C) 2005
* Copyright (C) 2003 2004 2005 Michel Xhaard
sonix decoder
* Bertrik.Sikken. (C) 2005
Spca561 decoder
* (C) 2005 Andrzej Szombierski [qq@NOSPAM]
Small jpeg decoder library (tinyjpeg)
Copyright (c) 2006, Luc Saillard <luc@NOSPAM>
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
- Neither the name of the author nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
jidctflt.c
Copyright (C) 1994-1998, Thomas G. Lane.
This file is part of the Independent JPEG Group's software.
The authors make NO WARRANTY or representation, either express or implied,
with respect to this software, its quality, accuracy, merchantability, or
fitness for a particular purpose. This software is provided "AS IS", and you,
its user, assume the entire risk as to its quality and accuracy.
This software is copyright (C) 1991-1998, Thomas G. Lane.
All Rights Reserved except as specified below.
Permission is hereby granted to use, copy, modify, and distribute this
software (or portions thereof) for any purpose, without fee, subject to these
conditions:
(1) If any part of the source code for this software is distributed, then this
README file must be included, with this copyright and no-warranty notice
unaltered; and any additions, deletions, or changes to the original files
must be clearly indicated in accompanying documentation.
(2) If only executable code is distributed, then the accompanying
documentation must state that "this software is based in part on the work of
the Independent JPEG Group".
(3) Permission for use of this software is granted only if the user accepts
full responsibility for any undesirable consequences; the authors accept
NO LIABILITY for damages of any kind.
These conditions apply to any software derived from or based on the IJG code,
not just to the unmodified library. If you use our work, you ought to
acknowledge us.
Permission is NOT granted for the use of any IJG author's name or company name
in advertising or publicity relating to this software or products derived from
it. This software may be referred to only as "the Independent JPEG Group's
software".
We specifically permit and encourage the use of this software as the basis of
commercial products, provided that all warranty or liability claims are
assumed by the product vendor.
This implementation is based on Arai, Agui, and Nakajima's algorithm for
scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in
Japanese, but the algorithm is described in the Pennebaker & Mitchell
JPEG textbook (see REFERENCES section in file README). The following code
is based directly on figure 4-8 in P&M.
libv4l-0.5.9/README:
====================
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 get in
the middle and emulate the format (if an app wants to know which formats the
hardware can _really_ do it should use ENUM_FMT, not randomly try a bunch of
S_FMT's). For more details on the v4l2_ functions see libv4l2.h .
wrappers
--------
The functionality provided by libv4l1 for v4l1 apps and libv4l2 for v4l2 apps
can also be used by existing apps without modifying them. For this purpose
2 wrapper libraries are provided which can be preloaded before starting the
application using the LD_PRELOAD environment variable. These wrappers will
then intercept calls to open/close/ioctl/etc. and if these calls directed
towards a video device the wrapper will redirect the call to the libv4lX
counterparts.
The preloadable libv4l1 wrapper which adds v4l2 device compatibility to v4l1
applications is called v4l1compat.so. The preloadable libv4l2 wrapper which
adds support for various pixelformats to v4l2 applications is called
v4l2convert.so.
Example usage (after install in default location):
$ export LD_PRELOAD=/usr/local/lib/libv4l/v4l1compat.so
$ camorama
Installation Instructions
-------------------------
Simple type the following commands from the libv4l-x.y.z directory
(adjusting PREFIX as desired):
make
make install PREFIX=/usr/local
Note: make install also supports the DESTDIR=... paramter for installation
into chroots.
FAQ
---
Q: Why libv4l, whats wrong with directly accessing v4l2 devices ?
Q: Do we really need yet another library ?
A: Current webcam using applications like ekiga contain code to handle many
different specific pixelformats webcam's use, but that code only supports a
small subset of all native webcam (compressed) pixelformats. Other current
v4l2 applications do not support anything but rgb pixelformats (xawtv for
example) and this will not work with most webcams at all.
With gspca being ported to v4l2 and thus decoding to normal formats being
removed from the device driver as this really belongs in userspace, ekiga
would need to be extended with many more often chip dependent formats, like
the bayer compression used by the spca561 and the (different) compression used
by the pac207 and the (again different) compression used by the sn9c102. Adding
support for all these formats should not be done at the application level, as
then it needs to be written for each application seperately. Licensing issues
with the decompressors will then also become a problem as just cut and pasting
from one application to another is bound to hit license incompatibilities.
So clearly this belongs in a library, and in a library with a license which
allows this code to be used from as many different applications as possible.
Hence libv4l was born.
Q: Under which license may I use and distribute libv4l?
A: All libv4l components are licensed under the GNU Library General Publishing
License version 2 or (at your option) any later version. See the included
COPYING.LIB file.
Q: Okay so I get the use of having a libv4lconvert, but why libv4l1 ?
A: Many v4l2 drivers do not offer full v4l1 compatibility. They often do not
implemented the CGMBUF ioctl and v4l1 style mmap call. Adding support to all
these drivers for this is a lot of work and more importantly unnecessary
adds code to kernel space.
Also even if the CGMBUF ioctl and v4l1 style mmap are supported, then most
cams still deliver pixelformats which v4l1 applications do not understand.
This libv4l1 was born as an easy way to get v4l1 applications to work with
v4l2 devices without requiring full v4l1 emulation (including format
conversion) in the kernel, and without requiring major changes to the
applications.
Q: Why should I use libv4l2 in my app instead of direct device access
combined with libv4lconvert?
libv4l2 is mainly meant for quickly and easily adding support for more
pixelformats to existing v4l2 applications. So if you feel better directly
accessing the device in combination with libv4lconvert thats fine too.
Notice that libv4l2 also does emulation of the read() call on devices which
do not support it in the driver. In the background this uses mmap buffers
(even on devices which do support the read call). This mmap gives libv4lconvert
zero-copy access to the captured frame, and then it can write the converted
data directly to the buffer the application provided to v4l2_read(). Thus
another reason to use liv4l2 is to get the no memcpy advantage of the mmap
capture method combined with the simplicity of making a simple read() call.
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