mirror of
https://mirror.skon.top/https://github.com/FFmpeg/FFmpeg
synced 2026-04-20 21:00:41 +08:00
bc012ac918
This is important for feature checking to work correctly.
It can happen that an unrecognized flag passes the compile test with
only a warning, while failing in preprocessor-only check with an error.
This causes all test_cpp calls to fail and silently produces arguably
broken MSVC builds. Also, all check_* functions don't work as expected,
because they assume the check passed, even though there was a warning.
Additionally, this brings the behavior in line with GCC/Clang based
builds, failing early on unrecognized flags instead of silently
continuing with warnings in the log.
The /options:strict option is available starting in Visual Studio 2022
version 17.0. Because of that, we cannot use check_cflags alone, as it
would add this flag for older MSVC versions and produce warnings. So, we
need to manually perform a version check. A bit of a chicken and egg
problem.
Perform the version check before adding extra flags from the user to
ensure we don't silently fail the preprocessor check due to invalid
flags on older MSVC versions. Note that behavior differs depending on
whether we are compiling or only preprocessing.
This fixes silent different between handling:
`cl.exe -P foo c.c`
c1: fatal error C1083: Cannot open source file: 'foo': No such file
or directory
`cl.exe -c foo c.c`
cl : Command line warning D9024 : unrecognized source file type
'foo', object file assumed
Where -P fails, while -c throws warnings only. Of course `foo` is
completely bogus here, but depends on the flags or configuration this
may be unsupported argument. Or even some converted path from MSYS when
run inside it. The objective is to always error out instead of silently
hiding this.
Use check_cflags even after the _MSC_FULL_VER check, for non-MSVC
compilers. For example Clang-CL impersonate MSVC, but does not support
-options:strict flag currently.
Signed-off-by: Kacper Michajłow <kasper93@gmail.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.