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Up until now, using a dynamic buffer entailed at least three allocations: One for the AVIOContext, one for the AVIOContext's opaque (which, among other things, contains the small write buffer), and one for the big buffer that is independently allocated that is returned when calling avio_close_dyn_buf(). It is possible to avoid the third allocation if one doesn't use a packetized dynamic buffer, if all the data written so far fit into the write buffer and if one does not require the actual (big) buffer to have an indefinite lifetime. This is done by making avio_get_dyn_buf() return a pointer to the data in the write buffer if nothing has been written to the main buffer yet. The dynamic buffer will then be freed using ffio_free_dynamic_buffer (which needed to be modified not to call avio_close_dyn_buf() internally). So a typical use-case like: size = avio_close_dyn_buf(dyn_pb, &buf); do something with buf av_free(buf); can be converted to: size = avio_get_dyn_buf(dyn_pb, &buf); do something with buf ffio_free_dynamic_buffer(&dyn_pb); In more complex scenarios this can simplify freeing as well, because it is now clear that freeing always has to be performed via ffio_free_dynamic_buffer(). Of course, in case this saves an allocation it also saves a memcpy. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
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 a mean to alter decoded Audio and Video through chain of 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.