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Ganesh Ajjanagadde 68e79b27a5 avutil/lls: speed up performance of solve_lls
This is a trivial rewrite of the loops that results in better
prefetching and associated cache efficiency. Essentially, the problem is
that modern prefetching logic is based on finite state Markov memory, a reasonable
assumption that is used elsewhere in CPU's in for instance branch
predictors.

Surrounding loops all iterate forward through the array, making the
predictor think of prefetching in the forward direction, but the
intermediate loop is unnecessarily in the backward direction.

Speedup is nontrivial. Benchmarks obtained by 10^6 iterations within
solve_lls, with START/STOP_TIMER. File is tests/data/fate/flac-16-lpc-cholesky.err.
Hardware: x86-64, Haswell, GNU/Linux.

new:
  17291 decicycles in solve_lls, 2096706 runs,    446 skips
  17255 decicycles in solve_lls, 4193657 runs,    647 skips
  17231 decicycles in solve_lls, 8384997 runs,   3611 skips
  17189 decicycles in solve_lls,16771010 runs,   6206 skips
  17132 decicycles in solve_lls,33544757 runs,   9675 skips
  17092 decicycles in solve_lls,67092404 runs,  16460 skips
  17058 decicycles in solve_lls,134188213 runs,  29515 skips

old:
  18009 decicycles in solve_lls, 2096665 runs,    487 skips
  17805 decicycles in solve_lls, 4193320 runs,    984 skips
  17779 decicycles in solve_lls, 8386855 runs,   1753 skips
  18289 decicycles in solve_lls,16774280 runs,   2936 skips
  18158 decicycles in solve_lls,33548104 runs,   6328 skips
  18420 decicycles in solve_lls,67091793 runs,  17071 skips
  18310 decicycles in solve_lls,134187219 runs,  30509 skips

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
2015-11-26 09:20:46 -05:00
compat os2threads: Add pthread_once() 2015-11-12 22:31:46 +01:00
doc avfilter/vf_stack: make it possible to stop with shortest stream 2015-11-26 10:02:00 +01:00
libavcodec aaccoder_twoloop: Mark sfdiff as av_unused 2015-11-26 03:46:09 -03:00
libavdevice avdevice/dshow_enummediatypes: check return of av_malloc 2015-11-06 09:36:57 -05:00
libavfilter avfilter/vf_stack: make it possible to stop with shortest stream 2015-11-26 10:02:00 +01:00
libavformat lavf/http: fix incorrect warning in range requests 2015-11-25 19:34:01 -06:00
libavresample Merge commit 'e2854e731f' 2015-11-10 18:07:41 +01:00
libavutil avutil/lls: speed up performance of solve_lls 2015-11-26 09:20:46 -05:00
libpostproc Merge commit 'e88103a7f9' 2015-09-05 21:35:46 +02:00
libswresample swresample/resample: remove redundant L for floating literal 2015-11-15 10:26:43 -05:00
libswscale swscale/arm: add ff_nv{12,21}_to_{argb,rgba,abgr,bgra}_neon 2015-11-23 14:47:12 +01:00
presets
tests fate-run: Fix indentation 2015-11-25 21:03:14 -08:00
tools patcheck: Fix false detection of 'mergeable calls' when line is removed 2015-11-23 00:34:14 +01:00
.gitattributes
.gitignore gitignore: ignore object file temporaries 2015-10-10 20:30:41 +02:00
.travis.yml Merge commit 'eda1832874' 2015-11-22 17:12:24 +00:00
arch.mak use mmi instead of loongson3 as simd-optimization flag 2015-07-07 03:46:57 +02:00
Changelog avformat: add FSB demuxer 2015-11-21 21:03:51 +01:00
cmdutils.c all: use FFDIFFSIGN to resolve possible undefined behavior in comparators 2015-11-03 16:28:30 -05:00
cmdutils.h cmdutils: remove sws_opts usage, simplify code 2015-08-08 16:51:25 +02:00
cmdutils_common_opts.h
cmdutils_opencl.c all: use FFDIFFSIGN to resolve possible undefined behavior in comparators 2015-11-03 16:28:30 -05:00
common.mak Merge commit 'c1aac39eac' 2015-10-14 13:54:50 +02:00
configure configure: Fix pseudo-German 2015-11-24 18:18:12 -08:00
COPYING.GPLv2
COPYING.GPLv3
COPYING.LGPLv2.1
COPYING.LGPLv3
CREDITS
ffmpeg.c ffmpeg: fix -copy_prior_start 0 with -copyts and input -ss 2015-11-20 19:20:30 +01:00
ffmpeg.h ffmpeg: Fixing typos and adding comments to fps code 2015-11-16 01:53:47 +01:00
ffmpeg_dxva2.c
ffmpeg_filter.c ffmpeg_filter: remove redundant null ptr check 2015-11-11 01:51:52 +01:00
ffmpeg_opt.c all: remove some casts of function pointer to void * 2015-10-24 15:14:59 -04:00
ffmpeg_qsv.c Merge commit 'fb472e1a11' 2015-10-22 16:18:02 +02:00
ffmpeg_vdpau.c ffmpeg_vdpau: Ignore decoder's max supported level 2015-08-16 15:02:33 -07:00
ffmpeg_videotoolbox.c ffmpeg/videotoolbox: protect UTGetOSTypeFromString on both VDA and VT 2015-10-15 10:22:31 +02:00
ffplay.c Replace remaining occurances of av_free_packet with av_packet_unref 2015-10-27 14:35:30 +01:00
ffprobe.c ffprobe: add support for printing packet strings metadata as packet tags 2015-10-30 20:47:43 +01:00
ffserver.c ffserver: Use AVOption API to access ffm demuxer instead of direct access depending on ABI 2015-11-20 20:03:12 +01:00
ffserver_config.c ffserver_config: check for INT_MIN before doing FFABS 2015-10-13 19:40:09 -04:00
ffserver_config.h ffserver: Use singlejpeg muxer for jpeg 2015-06-08 03:36:22 +02:00
INSTALL.md
library.mak build: add LDLIBFLAGS 2015-07-08 14:35:02 +02:00
LICENSE.md avfilter: add rubberband wrapper 2015-09-20 19:54:57 +02:00
MAINTAINERS lavfi: remove astreamsync. 2015-11-07 16:43:36 +01:00
Makefile Merge commit 'fb472e1a11' 2015-10-22 16:18:02 +02:00
README.md README: replace http with https 2015-10-06 13:27:29 +02:00
RELEASE RELEASE: update to 2.8.git 2015-09-09 23:53:15 -03:00
version.sh version.sh: add note that ffversion.h is auto-generated 2015-10-25 10:14:44 -04:00

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.
  • ffserver is a multimedia streaming server for live broadcasts.
  • 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. Few developers follow pull requests so they will likely be ignored.