4aa0665f39
The Matroska muxer uses a dynamic buffer to buffer the content of
Clusters before eventually writing them. Up until now, each time a
Cluster was written, the dynamic buffer was closed, i.e. freed; now it
is only reset, saving allocations of the AVIOContext itself, its opaque
as well as most of the reallocations of the buffer.
This is advantageous performance-wise, in particular on systems where
reallocations are slow (namely Windows). The following table shows the
decicyles for writing a frame on Linux (Ubuntu 19.10) and Windows (7)
on an x64 Haswell (to /dev/null on Linux, to stdout which is discarded
on Windows (the default values of the size and duration of clusters for
seekable output have been explicitly set in this case); in all tests,
writing CRC-32 values has been disabled in all tests; calls to the muxer's
write_packet function in write_packet() in libavformat/mux.c have been
timed; each of the following tests has been repeated 50 times):
| Windows before | Windows after | Linux before | Linux after
_________________________________________________________________
A | 979437 | 192304 | 259500 | 183320
B | 715936 | 155648 | 152786 | 130879
C | 265115 | 56034 | 78496 | 53243
D | 386224 | 80307 | 128894 | 75354
E | 21732 | 10695 | 11320 | 9801
(A is a 10.2 mb/s file with a GOP length of 2s, amounting to an average
Cluster size of about 2.5 MiB; the average Cluster size of B is 1.1 MiB;
for C it is 2.35 MiB, for D it is 0.46 MiB; for E - a file with just a
single audio track of 158kb/s resulting in a Cluster size of about 100
kB, the relative gains were the smallest, probably because of the small
Cluster size.)
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.