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Andreas Rheinhardt e6ea75a38d avformat/matroskaenc: Improve calculating EBML ID size
When the Matroska muxer writes an EBML ID, it calculates the length of
said ID before; and it does this as if this were a number that needs to
be encoded as EBML number: The formula used is (av_log2(id + 1) - 1) / 7
+ 1. But the constants used already contain the VINT_MARKER (the leading
bit indicating the length of the EBML number) and therefore the algorithm
used makes no sense. Instead the position of the most significant byte
set gives the desired length.

The algorithm used until now worked because EBML numbers are subject to
restrictions: If the EBML number takes up k bytes, then the bit 1 << (7
* k) is set and av_log2(id) is 7 * k. So the current algorithm produces
the correct result unless the EBML ID is of the form 7 * k - 1 because
of the "id + 1". But contrary to encoding lengths as EBML number (where
the + 1 exists to avoid the encodings reserved for unknown length),
such EBML numbers are simply forbidden as EBML IDs and as such none of
them were ever written.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2020-03-30 04:23:06 +02:00
compat avformat/udp: support w32pthreads compat 2020-03-08 19:08:04 +01:00
doc avformat/avformat: Update av_read_frame() documentation 2020-03-29 03:58:30 +02:00
ffbuild common.mak: Also clean Windows debug files. 2020-03-21 18:46:00 +01:00
fftools ffplay, avcodec, avformat: Don't initialize before av_packet_ref() 2020-03-28 04:17:20 +01:00
libavcodec nvdec: attach real hw_frames to post-processed frames 2020-03-28 17:58:54 +01:00
libavdevice remove CHAR_MIN/CHAR_MAX usage 2020-03-17 22:46:36 +01:00
libavfilter avfilter/vf_v360: fix swapped variables 2020-03-29 13:27:49 +02:00
libavformat avformat/matroskaenc: Improve calculating EBML ID size 2020-03-30 04:23:06 +02:00
libavresample avresample: remove deprecated attribute from the AVAudioResampleContext struct 2018-01-09 10:56:53 -03:00
libavutil avutil/frame: make frame copy functions hwframe aware 2020-03-28 17:59:32 +01:00
libpostproc libavcodec, libpostproc: Remove outcommented START/STOP_TIMER 2020-03-14 18:24:04 +01:00
libswresample Silence "string-plus-int" warning shown by clang. 2020-01-06 22:38:56 +01:00
libswscale lsws/input: Do not change transparency range. 2020-03-11 22:55:49 +01:00
presets
tests tests/checkasm: add overflow test for hevc_add_res 2020-03-27 10:57:40 +01:00
tools tools/target_dec_fuzzer: limit per frame samples for APE 2020-01-30 19:59:10 +01:00
.gitattributes fate: add SCC test 2017-01-27 17:06:42 +01:00
.gitignore tools/python: add script to convert TensorFlow model (.pb) to native model (.model) 2019-07-01 10:23:47 -03:00
.mailmap mailmap: Add another old mail address I used. 2020-02-27 13:02:06 +01:00
.travis.yml Merge commit '899ee03088' 2019-03-14 15:53:16 -03:00
Changelog avfilter: add vf_overlay_cuda 2020-03-28 18:39:40 +01:00
configure avfilter: add vf_overlay_cuda 2020-03-28 18:39:40 +01:00
CONTRIBUTING.md Add CONTRIBUTING.md 2016-09-18 10:02:13 +01:00
COPYING.GPLv2
COPYING.GPLv3
COPYING.LGPLv2.1
COPYING.LGPLv3
CREDITS
INSTALL.md INSTALL.md: Fix Markdown formatting 2019-01-31 10:29:16 -09:00
LICENSE.md avfilter/vf_geq: Relicense to LGPL 2019-12-28 11:20:48 +01:00
MAINTAINERS MAINTAINERS: add my gpg fingerprint 2020-03-23 23:37:19 +01:00
Makefile Makefile: Delete more created files when running "make distclean". 2020-03-11 11:43:01 +01:00
README.md Remove the ffserver program 2018-01-06 18:31:37 +00:00
RELEASE RELEASE: Update value for post 4.2 branch 2019-07-21 18:37:32 +02:00

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.
  • 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.