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lavu/tx: support in-place FFT transforms 
This commit adds support for in-place FFT transforms. Since our
internal transforms were all in-place anyway, this only changes
the permutation on the input.

Unfortunately, research papers were of no help here. All focused
on dry hardware implementations, where permutes are free, or on
software implementations where binary bloat is of no concern so
storing dozen times the transforms for each permutation and version
is not considered bad practice.
Still, for a pure C implementation, it's only around 28% slower
than the multi-megabyte FFTW3 in unaligned mode.

Unlike a closed permutation like with PFA, split-radix FFT bit-reversals
contain multiple NOPs, multiple simple swaps, and a few chained swaps,
so regular single-loop single-state permute loops were not possible.
Instead, we filter out parts of the input indices which are redundant.
This allows for a single branch, and with some clever AVX512 asm,
could possibly be SIMD'd without refactoring.

The inplace_idx array is guaranteed to never be larger than the
revtab array, and in practice only requires around log2(len) entries.

The power-of-two MDCTs can be done in-place as well. And it's
possible to eliminate a copy in the compound MDCTs too, however
it'll be slower than doing them out of place, and we'd need to dirty
the input array.
2021-02-21 17:05:16 +01:00
compat All: update names in copyright headers 2021-01-20 01:02:56 -06:00
doc lavu/tx: support in-place FFT transforms 2021-02-21 17:05:16 +01:00
ffbuild ffbuild/common: Make deletion of templates possible 2021-02-07 09:45:04 +01:00
fftools fftools/ffplay: reindent and some minor cosmetics 2021-02-19 21:30:13 +01:00
libavcodec avcodec: add Simbiosis IMX video decoder 2021-02-20 17:42:00 +01:00
libavdevice avdevice/avdevice: Deprecate AVDevice Capabilities API 2021-02-14 21:07:57 +01:00
libavfilter avfilter/af_afade: remove uneeded '.' from durations in options 2021-02-21 13:42:40 +01:00
libavformat avformat: add Simbiosis IMX demuxer 2021-02-20 17:43:17 +01:00
libavresample
libavutil lavu/tx: support in-place FFT transforms 2021-02-21 17:05:16 +01:00
libpostproc lavu/mem: move the DECLARE_ALIGNED macro family to mem_internal on next+1 bump 2021-01-01 14:14:57 +01:00
libswresample swresample/audioconvert: Fix left shift of negative value 2020-09-30 10:50:45 +02:00
libswscale swscale/x86/yuv2yuvX: use the movsxdifnidn helper macro 2021-02-18 18:47:43 -03:00
presets
tests tests/checkasm/sw_scale: use memset() to fill dither 2021-02-19 16:19:11 -03:00
tools tools/target_dec_fuzzer: Adjust threshold for wavpack 2021-02-16 19:02:24 +01:00
.gitattributes
.gitignore
.mailmap mailmap: add entry for myself 2020-07-13 11:24:04 +08:00
.travis.yml
Changelog avformat: add Simbiosis IMX demuxer 2021-02-20 17:43:17 +01:00
configure avcodec: add initial exr image encoder 2021-02-18 13:00:40 +01:00
CONTRIBUTING.md
COPYING.GPLv2
COPYING.GPLv3
COPYING.LGPLv2.1
COPYING.LGPLv3
CREDITS
INSTALL.md
LICENSE.md avfilter/vf_geq: Relicense to LGPL 2019-12-28 11:20:48 +01:00
MAINTAINERS MAINTAINERS: update names 2021-01-20 01:04:26 -06:00
Makefile tools/enum_options: fix build and add to Makefile 2020-11-20 15:20:24 +01:00
README.md
RELEASE RELEASE: We are after the 4.3 branch point, update for that 2020-06-10 00:20:24 +02:00

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

  • libavcodec provides implementation of a wider range of codecs.
  • libavformat implements streaming protocols, container formats and basic I/O access.
  • libavutil includes hashers, decompressors and miscellaneous utility functions.
  • libavfilter provides a mean to alter decoded Audio and Video through chain of filters.
  • libavdevice provides an abstraction to access capture and playback devices.
  • libswresample implements audio mixing and resampling routines.
  • libswscale implements 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, ismindex and qt-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.