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Up until now, libswscale/output.c used a macro to write an output pixel which involved a call to av_pix_fmt_desc_get() to find out whether the input pixel format is BE or LE despite this being known at compile-time (there are templates per pixfmt). Even worse, these calls are made in a loop, so that e.g. there are eight calls to av_pix_fmt_desc_get() for every pixel processed in yuv2rgba64_X_c_template() for 64bit RGB formats. This commit modifies these macros to ensure that isBE() is evaluated at compile-time. This saved 41184B of .text for me (GCC 11.2, -O3). Of course, it also improved performance. E.g. ffmpeg_g -f lavfi -i testsrc2,format=yuva420p -pix_fmt rgba64le \ -threads 1 -t 1:00 -f null - (which uses yuv2rgba64le_X_c, which is an invocation of yuv2rgba64_X_c_template() mentioned above), performance improved from 95589 to 41387 decicycles for one call to yuv2packedX; for the be variant the numbers went down from 76087 to 43024 decicycles. Reviewed-by: Anton Khirnov <anton@khirnov.net> Reviewed-by: Paul B Mahol <onemda@gmail.com> Reviewed-by: Michael Niedermayer <michael@niedermayer.cc> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.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.