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1)Some filters allow cross-referenced expressions e.g. x=y+10. In such cases, filters evaluate expressions multiple times for successful evaluation of all expressions. If the expression for one or more variables contains a RNG, the result may vary across evaluation leading to inconsistent values across the cross-referenced expressions. 2)A related case is circular expressions e.g. x=y+10 and y=x+10 which cannot be succesfully resolved. 3)Certain filter variables may only be applicable in specific eval modes and lead to a failure of evaluation in other modes e.g. pts is only relevant for frame eval mode. At present, there is no reliable means to identify these occurrences and thus the error messages provided are broad or inaccurate. The helper function introduced - av_expr_count_vars - allows developers to identify the use and count of variables in expressions and thus tailor the error message, allow for a graceful fallback and/or decide evaluation order.
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.