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QVBR mode is to use the variable bitrate control algorithm with constant quality. mfxExtCodingOption3 should be supported to enable QVBR mode. It is neccesary to specify a max_rate for QVBR, else it may be ICQ mode. Example usage: ffmpeg -hwaccel qsv -c:v h264_qsv -i input.mp4 -c:v h264_qsv -global_quality 25 -maxrate 2M test_qvbr.mp4 -v verbose Clip QVBR quality range to be [0, 51] as Mark's commments. It is similar to qp range of CQP but possibly should be updated when VP8/VP9 encoding can be supported. Reviewed-by: Mark Thompson <sw@jkqxz.net> Signed-off-by: Zhong Li <zhong.li@intel.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 a mean to alter decoded Audio and Video through chain of 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.