b9a25963f7
This introduces an optional dependency on lcms2 into FFmpeg. lcms2 is a widely used library for ICC profile handling, which apart from being used in almost all major image processing programs and video players, has also been deployed in browsers. As such, it's both widely available and well-tested. Add a few helpers to cover our major use cases. This commit merely introduces the helpers (and configure check), even though nothing uses them yet. It's worth pointing out that the reason the cmsToneCurves for each AVCOL_TRC are cached inside the context, is because constructing a cmsToneCurve requires evaluating the curve at 4096 (by default) grid points and constructing a LUT. So, we ideally only want to do this once per curve. This matters for e.g. ff_icc_profile_detect_transfer, which essentially compares a profile against all of these generated LUTs. Re-generating the LUTs for every iteration would be unnecessarily wasteful. The same consideration does not apply to e.g. cmsCreate*Profile, which is a very lightweight operation just involving struct allocation and setting a few pointers. The cutoff value of 0.01 was determined by experimentation. The lowest "false positive" delta I saw in practice was 0.13, and the largest "false negative" delta was 0.0008. So a value of 0.01 sits comfortaby almost exactly in the middle. Signed-off-by: Niklas Haas <git@haasn.dev>
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.