mirror of https://git.ffmpeg.org/ffmpeg.git
2275e70569
1. The loop counter of the substream_directory loop is always less than the number of substreams, yet within the loop it is checked whether it is less than FFMIN(3, s->hdr.num_substreams), although the check for < 3 would suffice. 2. In case the packet is a major sync packet, the last two bytes of the major sync structure were initialized to 0xff and then immediately overwritten afterwards without ever making use of the values just set. 3. When updating the parity_nibble during writing the new substream_directory, the parity_nibble is updated one byte at a time with bytes that might be read from the output packet's data. But one can do both bytes at the same time without resorting to the data just written by XOR'ing with the variable that contains the value that has just been written as a big endian number. This changes the intermediate value of parity_nibble, but in the end it just amounts to a reordering of the sum modulo two that will eventually be written as parity_nibble. Due to associativity and commutativity, this value is unchanged. 4. init_get_bits8 already checks that no overflow happens during the conversion of its argument from bytes to bits. ff_mlp_read_major_sync makes sure not to overread (the maximum size of a major_sync_info is 60 bytes anyway) and last_offset is < 2^13, so that no overflow in the calculation of size can happen, i.e. the check for whether size is >= 0 is unnecessary. But then size is completely unnecessary and can be removed. 5. In case the packet is just passed through, it is unnecessary to read the packet's dts. This is therefore postponed to when we know that the packet is not passed through. 6. Given that it seems overkill to use a bitreader just for one variable, the size of the input access unit is now read directly. 7. A substream's offset (of the end of the substream) is now stored as is (i.e. in units of words). These changes amount to a slight performance improvement: It improved from 5897 decicycles of ten runs with about 262144 runs each (including an insignificant amount -- about 20-25 usually of skips) to 5747 decicycles under the same conditions. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> |
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| compat | ||
| doc | ||
| ffbuild | ||
| fftools | ||
| libavcodec | ||
| libavdevice | ||
| libavfilter | ||
| libavformat | ||
| libavresample | ||
| libavutil | ||
| libpostproc | ||
| libswresample | ||
| libswscale | ||
| presets | ||
| tests | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| .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 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.