mirror of https://git.ffmpeg.org/ffmpeg.git
0183c2c830
The input is laid out in 16 segments, of which 13 actually need to be loaded. There are no really efficient ways to deal with this: 1) If we load 8 segments wit unit stride, then narrow to 16 segments with right shifts, we can only get one half-size vector per segment, or just 2 elements per vector (EMUL=1/2) - at least with 128-bit vectors. This ends up unsurprisingly about as fas as the C code. 2) The current approach is to load with strides. We keep that approach, but improve it using three 4-segmented loads instead of 12 single-segment loads. This divides the number of distinct loaded addresses by 4. 3) A potential third approach would be to avoid segmentation altogether and splat the scalar coefficient into vectors. Then we can use a unit-stride and maximum EMUL. But the downside then is that we have to multiply the 3 (of 16) unused segments with zero as part of the multiply-accumulate operations. In addition, we also reuse vectors mid-loop so as to increase the EMUL from 1 to 2, which also improves performance a little bit. Oeverall the gains are quite small with the device under test, as it does not deal with segmented loads very well. But at least the code is tidier, and should enjoy bigger speed-ups on better hardware implementation. Before: ps_hybrid_analysis_c: 1819.2 ps_hybrid_analysis_rvv_f32: 1037.0 (before) ps_hybrid_analysis_rvv_f32: 990.0 (after) |
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| compat | ||
| doc | ||
| ffbuild | ||
| fftools | ||
| libavcodec | ||
| libavdevice | ||
| libavfilter | ||
| libavformat | ||
| libavutil | ||
| libpostproc | ||
| libswresample | ||
| libswscale | ||
| presets | ||
| tests | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .travis.yml | ||
| CONTRIBUTING.md | ||
| COPYING.GPLv2 | ||
| COPYING.GPLv3 | ||
| COPYING.LGPLv2.1 | ||
| COPYING.LGPLv3 | ||
| CREDITS | ||
| Changelog | ||
| INSTALL.md | ||
| LICENSE.md | ||
| MAINTAINERS | ||
| Makefile | ||
| README.md | ||
| RELEASE | ||
| configure | ||
README.md
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.