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The cHRM chunk is descriptive. That is, it describes the primaries that should be used to interpret the pixel data in the PNG file. This is notably different from Mastering Display Metadata, which describes which subset of the presented gamut is relevant. MDM describes a gamut and says colors outside the gamut are not required to be preserved, but it does not actually describe the gamut that the pixel data from the frame resides in. Thus, to decode a cHRM chunk present in a PNG file to Mastering Display Metadata is incorrect. This commit changes this behavior so the cHRM chunk, if present, is decoded to color metadata. For example, if the cHRM chunk describes BT.709 primaries, the resulting AVFrame will be tagged with AVCOL_PRI_BT709, as a description of its pixel data. To do this, it utilizes libavutil/csp.h, which exposes a funcction av_csp_primaries_id_from_desc, to detect which enum value accurately describes the white point and primaries represented by the cHRM chunk. This commit also changes pngenc.c to utilize the libavuitl/csp.h API, since it previously duplicated code contained in that API. Instead, taking advantage of the API that exists makes more sense. pngenc.c does properly utilize the color tags rather than incorrectly using MDM, so that required no change. Signed-off-by: Leo Izen <leo.izen@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.