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FFmpeg git repo
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Andreas Rheinhardt 5b9a0e6031 avformat/matroskadec: Allow to count the number of element occurences 
Up until now, the generic EBML reader used by the Matroska demuxer did
not have the capability to record whether an element was actually
present or not; instead, in cases where it mattered one typically added
an invalid default value and checked whether the value is valid (in
which case it is guaranteed to be present). This worked pretty well so
far, yet the EBML specifications have evolved: It is now legal to use
zero-length elements for floats, ints, uints and strings (both ASCII and
UTF-8); the value of these elements is the default value of the element
(if it has one) or zero for scalar types and an empty string for
strings. Furthermore, having a default value does no longer imply that
the element may be presumed to be present (with its default value) if it
is absent; this is only true if the element is mandatory, too.

These rules are designed to allow size savings as follows: Consider the
newly added FlagOriginal: It being zero means the track is not in its
original language, it being one means it is. For backward compatibility
reasons, neither of the two values may be inferred automatically in the
absence of the element. But one can still save a byte when one wants to
write the element with a value of zero, as one can write the integer with
a length of zero: 0x55AE 80 instead of 0x55AE 81 00. In the former case,
a parser has to infer the value of the element to be zero (which is the
element's default value).

When encountering an element with length zero, our parser always infers
a value of zero (or an empty string); this is wrong for values with
a different default value. It needs to infer the default value (or zero
in its absence) and this precludes using an invalid default value for
elements like FlagOriginal. Ergo one needs to be able to record whether
an element is present or not by other means. This patch allows to use a
simple counter for this. While just at it, some invalid and unnecessary
default values have been removed (mastering metadata elements used
default values of -1.0, despite these elements only being used if they
are > 0).

Reviewed-by: Ridley Combs <rcombs@rcombs.me>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2021-02-22 03:57:16 +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/matroskadec: Allow to count the number of element occurences 2021-02-22 03:57:16 +01:00
libavresample
libavutil arm/aarch64: Use mach_absolute_time as timer on apple platforms 2021-02-21 22:41:34 +02:00
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 fate/matroska: Add test for mastering display metadata 2021-02-22 03:45:38 +01:00
tools tools/target_dec_fuzzer: Adjust threshold for wavpack 2021-02-16 19:02:24 +01:00
.gitattributes
.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 entry for myself 2020-07-13 11:24:04 +08:00
.travis.yml Merge commit '899ee03088d55152a48830df0899887f055da1de' 2019-03-14 15:53:16 -03:00
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.