No description
0e32192548
If __riscv_hwprobe() fails, then the kernel version is presumably too old. There is not much point falling back to the auxillary vector. - The Linux kernel requires I, so the flag is always set on Linux, and run-time detection is unnecessary. Our RISC-V assembler does anyway not support targets without I. - Linux can compile with or without F and D, but it cannot perform run-time detection for them (a kernel with F support will not boot a processor without F). The run-time detection is thus useless in that case. Besides F and D extensions are used throughout the C code, so their run-time detection would not be practical. - Support for V was added in a later kernel version than riscv_hwprobe(), so the system call will always be available if the kernel supports V. The only exception would be vendor kernel forks, but those are known to haphasardly pretend to support V on systems without actual V support, or with only pre-ratification binary-incompatible version. Furthermore, a large chunk of our optimisations require Zba and/or Zbb which cannot be detected with HWCAP in those kernels. For what it is worth, OpenJDK already took a similar action. Note that this keeps AT_HWCAP usage for platforms with neither C run-time <sys/hwprobe.h> nor kernel <asm/hwprobe.h>, notably kernels other than Linux. |
||
|---|---|---|
| compat | ||
| doc | ||
| ffbuild | ||
| fftools | ||
| libavcodec | ||
| libavdevice | ||
| libavfilter | ||
| libavformat | ||
| libavutil | ||
| libpostproc | ||
| libswresample | ||
| libswscale | ||
| presets | ||
| tests | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| Changelog | ||
| configure | ||
| CONTRIBUTING.md | ||
| COPYING.GPLv2 | ||
| COPYING.GPLv3 | ||
| COPYING.LGPLv2.1 | ||
| COPYING.LGPLv3 | ||
| CREDITS | ||
| INSTALL.md | ||
| LICENSE.md | ||
| MAINTAINERS | ||
| Makefile | ||
| README.md | ||
| RELEASE | ||
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.