README.static-linking - imx-gst-plugins-base - Git at Google


            
            =================================

            
             GStreamer Static Linking README

            
            =================================


            DRAFT, April 2013


               I. INTRODUCTION


            It is possible to link GStreamer libraries, plugins and applications

            
            statically, both in case of free/libre/open-source software applications

            
            and proprietary applications. On some platforms static linking may even

            
            be required.


            However, distributing statically linked binaries using GStreamer usually

            
            requires additional effort to stay compliant with the GNU LGPL v2.1 license.


            The purpose of this document is to draw attention to this fact, and to

            
            summarise in layman's terms what we believe is required from anyone

            
            distributing statically linked GStreamer binaries. Most of this also

            
            applies to dynamically linked GStreamer binaries.


               II. DISCLAIMER


            This document is not legal advice, nor is it comprehensive. It may use

            
            words in ways that do not match the definition or use in the license

            
            text. It may even be outright wrong. Read the license text for all the

            
            details, it is the only legally binding document in this respect.


            This document is primarily concerned with the implications for the

            
            distribution of binaries based on LGPL-licensed software as imposed by

            
            the LGPL license, but there may be other restrictions to the distribution

            
            of such binaries, such as terms and conditions of distribution channels

            
            (e.g. "app stores").


               III. THE SPIRIT OF THE LGPL LICENSE


            The GNU LGPL v2.1 license allows use of such-licensed software by

            
            proprietary applications, but still aims to ensure that at least the

            
            LGPL-licensed software parts remain free under all circumstances. This

            
            means any changes to LGPL-licensed source code must be documented and

            
            be made available on request to those who received binaries of the

            
            software. It also means that it must be possible to make changes to the

            
            LGPL-licensed software parts and make the application use those, as far

            
            as that is possible. And that recipients of an application using

            
            LGPL-licensed software are made aware of their rights according to the

            
            LGPL license.


            In an environment where GStreamer libraries and plugins are used as

            
            dynamically-loaded shared objects (DLL/.so/.dyn files), this is usually

            
            not a big problem, because it is fairly easy to compile a modified version

            
            of the GStreamer libraries or LGPL plugins, and the application will/should

            
            just pick up and use the modified version automatically. All that is needed

            
            is for the original, LGPL-licensed source code and source code modifications

            
            to be made available, and for a way to build the libraries or plugins for

            
            the platform required (usually that will be using the build system scripts

            
            that come with GStreamer, and using the typical build environment on the

            
            system in question, but where that is not the case the needed build scripts

            
            and/or tools would need to be provided as well).


               IV. THINGS YOU NEED TO DO


              * You must tell users of your application that you are using LGPL-licensed

            
                software, which LGPL-licensed software exactly, and you must provide them

            
                with a copy of the license so they know their rights under the LGPL.


              * You must provide (on request) all the source code and all the changes

            
                or additions you have made to the LGPL-licensed software you are using.


                For GStreamer code we would recommend that the changes be provided either

            
                in form of a branch in a git repository, or as a set of "git format-patch"-

            
                style patches against a GStreamer release or a snapshot of a GStreamer git

            
                repository. The patches should ideally say what was changed and why it

            
                was changed, and there should ideally be separate patches for independent

            
                changes.


              * You must provide a way for users of your application to make changes to

            
                the LGPL-licensed parts of the code, and re-create a full application

            
                binary with the changes (using the standard toolchain and tools of the

            
                target platform; if you are using a custom toolchain or custom tools

            
                you must provide these and document how to use them to create a new

            
                application binary).


                Note that this of course does not mean that the user is allowed to

            
                re-distribute the changed application. Nor does it mean that you have

            
                to provide your proprietary source code - it is sufficient to provide a

            
                ready-made compiled object file that can be relinked into an application

            
                binary with the re-compiled LGPL components.


               V. THINGS TO LOOK OUT FOR


            While most GStreamer plugins and the libraries they depend on are licensed

            
            under the LGPL or even more permissive licenses, that is not the case for

            
            all plugins and libraries used, esp. those in the gst-plugins-ugly or

            
            some of those in the gst-plugins-bad set of plugins.


            When statically linking proprietary code, care must be taken not to

            
            statically link plugins or libraries that are licensed under less permissive

            
            terms than the LGPL, such as e.g. GPL-licensed libraries.


               VI. SPECIAL CONSIDERATIONS FOR SPECIFIC USE-CASES


               1. Proprietary GStreamer/GLib-based Application On iOS


            Let's assume an individual or a company wants to distribute a proprietary

            
            iOS application that is built on top of GStreamer and GLib through

            
            Apple's App Store. At the time of writing the Apple iPhone developer

            
            agreement didn’t allow the bundling of shared libraries, so distributing

            
            a proprietary iOS application with shared libraries is only possible using

            
            distribution mechanisms outside of the App Store and/or only to jailbroken

            
            devices, a prospect that may not appeal to our individual or company. So the

            
            only alternative then is to link everything statically, which means the

            
            obligations mentioned above come into play.


               2. Example: Jabber on iOS


            Tandberg (now Cisco) created a Jabber application for iOS, based on GStreamer.

            
            On request they provided an LGPL compliance bundle in form of a zip file, with

            
            roughly the following contents:


            buildapp.sh

            
            readme.txt

            
            Jabber/Jabber-Info.plist

            
            Jabber/libip.a [236MB binary with proprietary code]

            
            Jabber/main.mm

            
            Jabber/xcconfig/Application.xcconfig

            
            Jabber/xcconfig/Debug.xcconfig

            
            Jabber/xcconfig/Release.xcconfig

            
            Jabber/xcconfig/Shared.xcconfig

            
            Jabber/Resources/*.lproj/Localizable.strings

            
            Jabber/Resources/{Images,Audio,Sounds,IB,Message Styles,Emoticons,Fonts}/*

            
            Jabber/Resources/*

            
            Jabber.xcodeproj/project.pbxproj

            
            Jabber.xcodeproj/project.xcworkspace/contents.xcworkspacedata

            
            opensource/build/config.site

            
            opensource/build/m4/movi.m4

            
            opensource/build/scripts/clean-deps.sh

            
            opensource/build/scripts/fixup-makefile.sh

            
            opensource/build/scripts/MoviMaker.py

            
            opensource/build.sh

            
            opensource/env.sh

            
            opensource/Makefile

            
            opensource/external/glib/*

            
            opensource/external/gstreamer/{gstreamer,gst-plugins-*}/*

            
            opensource/external/openssl/*

            
            opensource/external/proxy-libintl/*

            
            opensource/toolchain/darwin-x86/bin/{misc autotoools,m4,glib-mkenums,glib-genmarshal,libtool,pkg-config,etc.}

            
            opensource/toolchain/darwin-x86/share/{aclocal,aclocal-1.11,autoconf,automake-1.11,libtool}/*

            
            opensource/toolchain/darwin-x86/share/Config.pm

            
            opensource/toolchain/darwin-x86/share/Config.pm.movi.in

            
            patches/glib/glib.patch

            
            patches/gst-plugins-bad/gst-plugins-bad.patch

            
            patches/gst-plugins-base/gst-plugins-base.patch

            
            patches/gst-plugins-good/gst-plugins-good.patch

            
            patches/gstreamer/gstreamer.patch

            
            patches/openssl/openssl.patch


            readme.txt starts with "This Readme file describes how to build the Cisco

            
            Jabber for iPad application. You need to install Xcode, but the final package

            
            is built by running buildapp.sh." and describes how to build project,

            
            prerequisites, the procedure in detail, and a "How to Include Provisioning

            
            Profile Manually / Alternate Code Signing Instructions" section.


               3. Random Links Which May Be Of Interest


            [0] http://multinc.com/2009/08/24/compatibility-between-the-iphone-app-store-and-the-lgpl/
	=================================
	GStreamer Static Linking README
	=================================

	DRAFT, April 2013


	I. INTRODUCTION

	It is possible to link GStreamer libraries, plugins and applications
	statically, both in case of free/libre/open-source software applications
	and proprietary applications. On some platforms static linking may even
	be required.

	However, distributing statically linked binaries using GStreamer usually
	requires additional effort to stay compliant with the GNU LGPL v2.1 license.

	The purpose of this document is to draw attention to this fact, and to
	summarise in layman's terms what we believe is required from anyone
	distributing statically linked GStreamer binaries. Most of this also
	applies to dynamically linked GStreamer binaries.


	II. DISCLAIMER

	This document is not legal advice, nor is it comprehensive. It may use
	words in ways that do not match the definition or use in the license
	text. It may even be outright wrong. Read the license text for all the
	details, it is the only legally binding document in this respect.

	This document is primarily concerned with the implications for the
	distribution of binaries based on LGPL-licensed software as imposed by
	the LGPL license, but there may be other restrictions to the distribution
	of such binaries, such as terms and conditions of distribution channels
	(e.g. "app stores").


	III. THE SPIRIT OF THE LGPL LICENSE

	The GNU LGPL v2.1 license allows use of such-licensed software by
	proprietary applications, but still aims to ensure that at least the
	LGPL-licensed software parts remain free under all circumstances. This
	means any changes to LGPL-licensed source code must be documented and
	be made available on request to those who received binaries of the
	software. It also means that it must be possible to make changes to the
	LGPL-licensed software parts and make the application use those, as far
	as that is possible. And that recipients of an application using
	LGPL-licensed software are made aware of their rights according to the
	LGPL license.

	In an environment where GStreamer libraries and plugins are used as
	dynamically-loaded shared objects (DLL/.so/.dyn files), this is usually
	not a big problem, because it is fairly easy to compile a modified version
	of the GStreamer libraries or LGPL plugins, and the application will/should
	just pick up and use the modified version automatically. All that is needed
	is for the original, LGPL-licensed source code and source code modifications
	to be made available, and for a way to build the libraries or plugins for
	the platform required (usually that will be using the build system scripts
	that come with GStreamer, and using the typical build environment on the
	system in question, but where that is not the case the needed build scripts
	and/or tools would need to be provided as well).


	IV. THINGS YOU NEED TO DO

	* You must tell users of your application that you are using LGPL-licensed
	software, which LGPL-licensed software exactly, and you must provide them
	with a copy of the license so they know their rights under the LGPL.

	* You must provide (on request) all the source code and all the changes
	or additions you have made to the LGPL-licensed software you are using.

	For GStreamer code we would recommend that the changes be provided either
	in form of a branch in a git repository, or as a set of "git format-patch"-
	style patches against a GStreamer release or a snapshot of a GStreamer git
	repository. The patches should ideally say what was changed and why it
	was changed, and there should ideally be separate patches for independent
	changes.

	* You must provide a way for users of your application to make changes to
	the LGPL-licensed parts of the code, and re-create a full application
	binary with the changes (using the standard toolchain and tools of the
	target platform; if you are using a custom toolchain or custom tools
	you must provide these and document how to use them to create a new
	application binary).

	Note that this of course does not mean that the user is allowed to
	re-distribute the changed application. Nor does it mean that you have
	to provide your proprietary source code - it is sufficient to provide a
	ready-made compiled object file that can be relinked into an application
	binary with the re-compiled LGPL components.


	V. THINGS TO LOOK OUT FOR

	While most GStreamer plugins and the libraries they depend on are licensed
	under the LGPL or even more permissive licenses, that is not the case for
	all plugins and libraries used, esp. those in the gst-plugins-ugly or
	some of those in the gst-plugins-bad set of plugins.

	When statically linking proprietary code, care must be taken not to
	statically link plugins or libraries that are licensed under less permissive
	terms than the LGPL, such as e.g. GPL-licensed libraries.


	VI. SPECIAL CONSIDERATIONS FOR SPECIFIC USE-CASES


	1. Proprietary GStreamer/GLib-based Application On iOS

	Let's assume an individual or a company wants to distribute a proprietary
	iOS application that is built on top of GStreamer and GLib through
	Apple's App Store. At the time of writing the Apple iPhone developer
	agreement didn’t allow the bundling of shared libraries, so distributing
	a proprietary iOS application with shared libraries is only possible using
	distribution mechanisms outside of the App Store and/or only to jailbroken
	devices, a prospect that may not appeal to our individual or company. So the
	only alternative then is to link everything statically, which means the
	obligations mentioned above come into play.


	2. Example: Jabber on iOS

	Tandberg (now Cisco) created a Jabber application for iOS, based on GStreamer.
	On request they provided an LGPL compliance bundle in form of a zip file, with
	roughly the following contents:

	buildapp.sh
	readme.txt
	Jabber/Jabber-Info.plist
	Jabber/libip.a [236MB binary with proprietary code]
	Jabber/main.mm
	Jabber/xcconfig/Application.xcconfig
	Jabber/xcconfig/Debug.xcconfig
	Jabber/xcconfig/Release.xcconfig
	Jabber/xcconfig/Shared.xcconfig
	Jabber/Resources/*.lproj/Localizable.strings
	Jabber/Resources/{Images,Audio,Sounds,IB,Message Styles,Emoticons,Fonts}/*
	Jabber/Resources/*
	Jabber.xcodeproj/project.pbxproj
	Jabber.xcodeproj/project.xcworkspace/contents.xcworkspacedata
	opensource/build/config.site
	opensource/build/m4/movi.m4
	opensource/build/scripts/clean-deps.sh
	opensource/build/scripts/fixup-makefile.sh
	opensource/build/scripts/MoviMaker.py
	opensource/build.sh
	opensource/env.sh
	opensource/Makefile
	opensource/external/glib/*
	opensource/external/gstreamer/{gstreamer,gst-plugins-}/
	opensource/external/openssl/*
	opensource/external/proxy-libintl/*
	opensource/toolchain/darwin-x86/bin/{misc autotoools,m4,glib-mkenums,glib-genmarshal,libtool,pkg-config,etc.}
	opensource/toolchain/darwin-x86/share/{aclocal,aclocal-1.11,autoconf,automake-1.11,libtool}/*
	opensource/toolchain/darwin-x86/share/Config.pm
	opensource/toolchain/darwin-x86/share/Config.pm.movi.in
	patches/glib/glib.patch
	patches/gst-plugins-bad/gst-plugins-bad.patch
	patches/gst-plugins-base/gst-plugins-base.patch
	patches/gst-plugins-good/gst-plugins-good.patch
	patches/gstreamer/gstreamer.patch
	patches/openssl/openssl.patch

	readme.txt starts with "This Readme file describes how to build the Cisco
	Jabber for iPad application. You need to install Xcode, but the final package
	is built by running buildapp.sh." and describes how to build project,
	prerequisites, the procedure in detail, and a "How to Include Provisioning
	Profile Manually / Alternate Code Signing Instructions" section.


	3. Random Links Which May Be Of Interest

	[0] http://multinc.com/2009/08/24/compatibility-between-the-iphone-app-store-and-the-lgpl/