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librempeg/LICENSE.md
Timothy Gu 9ba54c1b82 avcodec: Remove libaacplus 
TODO: bump minor

It's inferior in quality to fdk-aac and has an arguably more problematic
license.

As early as 2012, a HydrogenAudio user reported:

> It has however one huge advantage: much better quality at low bitrates than
> faac and libaacplus.

(https://hydrogenaud.io/index.php?PHPSESSID=ckiq394pdglka0kj2fin6ij8t7&topic=95989.msg804633#msg804633)

I myself have made a few spectrograms for a comparison of the two
encoders as well. The FDK output is consistently better than the
libaacplus one, in all bitrates I tested.

libaacplus license is 3GPP + LGPLv2. 3GPP copyright notice is completely
proprietory, as follows:

> No part may be reproduced except as authorized by written permission.
>
> The copyright and the foregoing restriction extend to reproduction in
> all media.
>
> © 2008, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC).
>
> All rights reserved.

(The latest 26410-d00 zip from 3GPP has the same notice, but the copyright
year is changed to 2015)

The copyright part of the FDK AAC license (section 2) is a copyleft
license that permits redistribution under certain conditions (and
therefore the LGPL + libfdk-aac combination is not prohibited by
configure):

> Redistribution and use in source and binary forms, with or without
> modification, are permitted without payment of copyright license fees
> provided that you satisfy the following conditions:
>
> You must retain the complete text of this software license in
> redistributions of the FDK AAC Codec or your modifications thereto in
> source code form.
>
> You must retain the complete text of this software license in the
> documentation and/or other materials provided with redistributions of
> the FDK AAC Codec or your modifications thereto in binary form.
>
> You must make available free of charge copies of the complete source
> code of the FDK AAC Codec and your modifications thereto to recipients
> of copies in binary form.
>
> The name of Fraunhofer may not be used to endorse or promote products
> derived from this library without prior written permission.
>
> You may not charge copyright license fees for anyone to use, copy or
> distribute the FDK AAC Codec software or your modifications thereto.
>
> Your modified versions of the FDK AAC Codec must carry prominent
> notices stating that you changed the software and the date of any
> change. For modified versions of the FDK AAC Codec, the term
> "Fraunhofer FDK AAC Codec Library for Android" must be replaced by the
> term "Third-Party Modified Version of the Fraunhofer FDK AAC Codec
> Library for Android."
2016-01-29 17:14:37 -08:00

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#FFmpeg:

Most files in FFmpeg 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 FFmpeg.

Some optional parts of FFmpeg 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, FFmpeg's license changes to GPL v2+.

Specifically, the GPL parts of FFmpeg are:

  • libpostproc
  • optional x86 optimizations in the files
    • libavcodec/x86/flac_dsp_gpl.asm
    • libavcodec/x86/idct_mmx.c
    • libavfilter/x86/vf_removegrain.asm
  • libutvideo encoding/decoding wrappers in libavcodec/libutvideo*.cpp
  • the X11 grabber in libavdevice/x11grab.c
  • the swresample test app in libswresample/swresample-test.c
  • the texi2pod.pl tool
  • the following filters in libavfilter:
    • f_ebur128.c
    • vf_blackframe.c
    • vf_boxblur.c
    • vf_colormatrix.c
    • vf_cover_rect.c
    • vf_cropdetect.c
    • vf_delogo.c
    • vf_eq.c
    • vf_find_rect.c
    • vf_fspp.c
    • vf_geq.c
    • vf_histeq.c
    • vf_hqdn3d.c
    • vf_interlace.c
    • vf_kerndeint.c
    • vf_mcdeint.c
    • vf_mpdecimate.c
    • vf_owdenoise.c
    • vf_perspective.c
    • vf_phase.c
    • vf_pp.c
    • vf_pp7.c
    • vf_pullup.c
    • vf_sab.c
    • vf_smartblur.c
    • vf_repeatfields.c
    • vf_spp.c
    • vf_stereo3d.c
    • vf_super2xsai.c
    • vf_tinterlace.c
    • vf_uspp.c
    • vsrc_mptestsrc.c

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.

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.
  • tests/reference.pnm is under the expat license.

external libraries

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

compatible libraries

The following libraries are under GPL:

  • frei0r
  • libcdio
  • librubberband
  • libutvideo
  • libvidstab
  • libx264
  • libx265
  • libxavs
  • libxvid

When combining them with FFmpeg, FFmpeg 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 FFmpeg, the license version needs to be upgraded by passing --enable-version3 to configure.

incompatible libraries

The Fraunhofer AAC library and FAAC are under licenses which are incompatible with the GPLv2 and v3. We do not know for certain if their licenses are compatible with the LGPL. If you wish to enable these libraries, pass --enable-nonfree to configure. But note that if you enable any of these libraries the resulting binary will be under a complex license mix that is more restrictive than the LGPL and that may result in additional obligations. It is possible that these restrictions cause the resulting binary to be unredistributeable.