a78173374a
Currently, $(CPPFLAGS) and $(CFLAGS) are prepended to CXXFLAGS (the flags for compiling C++) like this: CXXFLAGS := $(CPPFLAGS) $(CFLAGS) $(CXXFLAGS) Using ":=" creates a simply expanded variable, i.e. the values of the variable at the time of assignment are used and later modifications to them are ignored (using a recursively expanding variable (i.e. "=" instead of ":=") is not really possible here, as there would be an infinite loop when evaluating CXXFLAGS). Yet we perform later additions to CPPFLAGS: HAVE_AV_CONFIG_H and BUILDING_libfoo are defined. These do not reach C++ compilations. To fix this a trick is employed to prepend to a recursively expanded variable while keeping it recursively expanded. There are two practical consequences of this: C++ files now no longer include the version.h header, but only the version_major.h header of their library, saving some recompilations. Furthermore, they now get some optimized math functions (namely the ones from lavu/intmath.h instead of the ones from lavu/common.h). (av_parity() is the only one for which it makes a difference.) Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides means to alter decoded audio and video through a directed graph of connected filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process and will be ignored.