mirror of https://git.ffmpeg.org/ffmpeg.git
b845fff57d
This muxer currently uses two ways to ensure that no bytes are wasted by writing unnecessary long EBML length fields for Master elements and the (Simple)Block element (all the other elements are fine as one either already has the right length or getting the actual length is easy and necessary anyway): Either use an upper bound that is good enough in case one is available or write the data into a dynamic buffer first to get the length; the former approach is impossible in lots of cases, whereas the latter incurs allocations and memcpying. It is therefore unfeasible to use the latter for e.g. the attachments or the BlockGroups. This patch adds a third alternative to complement the other two: It consists of an EbmlWriter that one can add EBML elements to that can be written later by calling ebml_writer_write(); the latter function first traverses the written elements recursively and calculates the length of each element; then a second pass is performed in which all the elements are written directly (without any seeks). This new API also performs checks for overlong elements; this is in contrast to put_ebml_string() which simply performs a size_t->int conversion even for strings originating from the user. The new API is designed to have very low overhead: It uses stack arrays and performs no allocations; this also comes at a price: Right now, it can only be used in contexts in which there is a compile-time upper bound for the number of elements. It is also incompatible with storing the offset of an element in order to update this field later. Furthermore, it puts the onus of memory management (i.e. ensuring that pointers stay valid) on the user. These restrictions might be overcome in the future. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com> |
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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.