Libav:
======

Most files in Libav are under the GNU Lesser General Public License version 2.1
or later (LGPL v2.1+). Read the file COPYING.LGPLv2.1 for details. Some other
files have MIT/X11/BSD-style licenses. In combination the LGPL v2.1+ applies to
Libav.

Some optional parts of Libav are licensed under the GNU General Public License
version 2 or later (GPL v2+). See the file COPYING.GPLv2 for details. None of
these parts are used by default, you have to explicitly pass --enable-gpl to
configure to activate them. In this case, Libav's license changes to GPL v2+.

Specifically, the GPL parts of Libav are

- the X11 grabber in libavdevice/x11grab.c
- the texi2pod.pl tool
- the following filters in libavfilter:
    - vf_blackframe.c
    - vf_boxblur.c
    - vf_cropdetect.c
    - vf_delogo.c
    - vf_hqdn3d.c
    - vf_yadif.c

There are a handful of files under other licensing terms, namely:

* The files libavcodec/jfdctfst.c, libavcodec/jfdctint_template.c and
  libavcodec/jrevdct.c are taken from libjpeg, see the top of the files for
  licensing details. Specifically note that you must credit the IJG in the
  documentation accompanying your program if you only distribute executables.
  You must also indicate any changes including additions and deletions to
  those three files in the documentation.

Should you, for whatever reason, prefer to use version 3 of the (L)GPL, then
the configure parameter --enable-version3 will activate this licensing option
for you. Read the file COPYING.LGPLv3 or, if you have enabled GPL parts,
COPYING.GPLv3 to learn the exact legal terms that apply in this case.


external libraries
==================

Libav can be combined with a number of external libraries, which sometimes
affect the licensing of binaries resulting from the combination.

compatible libraries
--------------------

The libcdio, libx264, libxavs and libxvid libraries are under GPL. When
combining them with Libav, Libav needs to be licensed as GPL as well by
passing --enable-gpl to configure.

The OpenCORE and VisualOn libraries are under the Apache License 2.0. That
license is incompatible with the LGPL v2.1 and the GPL v2, but not with
version 3 of those licenses. So to combine these libraries with Libav, the
license version needs to be upgraded by passing --enable-version3 to configure.

incompatible libraries
----------------------

The Fraunhofer AAC library, FAAC and OpenSSL are under licenses incompatible
with all (L)GPL versions. Thus, unfortunately, since both licenses cannot be
satisfied simultaneously, binaries resulting from the combination of Libav
with these libraries are nonfree und unredistributable. If you wish to enable
any of these libraries nonetheless, pass --enable-nonfree to configure.