1
0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-12-23 12:43:46 +02:00
Go to file
Andreas Rheinhardt efeb3a53ad avformat/matroskaenc: Avoid unnecessary seek
The Matroska muxer has a pair of functions designed to write master
elements whose exact length is not known in advance: start_ebml_master()
and end_ebml_master(). The first one of these would write the EBML ID of
the master element that is about to be started, reserve some bytes for
the length field and record the current position as well as how many
bytes were used for the length field. When writing the master's contents
is finished, end_ebml_master() gets the current position (at the end of
the master element), seeks to the length field using the recorded
position, writes the length field and seeks back to the end of the
master element so that one can continue writing other elements.

But if one wants to modify the content of the master element itself,
then the seek back is superfluous. This is the scenario that presents
itself when writing the trailer: One wants to update several elements
contained in the Segment master element (this is the main/root master
element of a Matroska file) that were already written when writing the
header. The current approach is to seek to the beginning of the file
to update the elements, then seek to the end, call end_ebml_master()
which immediately seeks to the beginning to write the length and seeks
back. The seek to the end (which has only been performed because
end_ebml_master() uses the initial position to determine the length
of the master element) and the seek back are of course superfluous.

This commit avoids these seeks by no longer using start/end_ebml_master()
to write the segment's length field. Instead, it is now written
manually. The new approach is: Seek to the beginning to write the length
field, then update the elements (in the order they appear in the file)
and seek back to the end.

This reduces the ordinary amount of seeks of the Matroska muxer to two
(ordinary excludes scenarios where one has big Chapters or Attachments
or where one writes the Cues at the front).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2020-05-19 01:26:07 +02:00
compat compat/avisynth: remove avisynth headers 2020-04-05 01:17:55 +02:00
doc avutil: bump version after addition of av_sat_add64 and av_sat_sub64 2020-05-17 16:05:15 -03:00
ffbuild common.mak: Also clean Windows debug files. 2020-03-21 18:46:00 +01:00
fftools fftools/ffmpeg: use local variable with same contents directly 2020-05-06 23:02:00 +08:00
libavcodec avcodec/frame_thread_encoder: check for frame threading codec cap instead of intra only 2020-05-18 12:39:34 -03:00
libavdevice avdevice/v4l2enc: Allow writing non-rawvideos to v4l2. 2020-05-09 15:44:43 +01:00
libavfilter avfilter/vsrc_sierpinski: unbreak configuring rate value 2020-05-16 11:13:46 +02:00
libavformat avformat/matroskaenc: Avoid unnecessary seek 2020-05-19 01:26:07 +02:00
libavresample avresample: remove deprecated attribute from the AVAudioResampleContext struct 2018-01-09 10:56:53 -03:00
libavutil lavc/qsvdec: add decode support for HEVC 4:2:2 8-bit and 10-bit 2020-05-18 13:32:50 +08:00
libpostproc libavcodec, libpostproc: Remove outcommented START/STOP_TIMER 2020-03-14 18:24:04 +01:00
libswresample Silence "string-plus-int" warning shown by clang. 2020-01-06 22:38:56 +01:00
libswscale swscale: aarch64: Add a NEON implementation of interleaveBytes 2020-05-15 23:38:17 +03:00
presets
tests avformat/matroskaenc: Don't reserve space for duration when unseekable 2020-05-19 01:03:05 +02:00
tools tools/target_dec_fuzzer: Adjust threshold for PNG and APNG 2020-05-10 01:09:13 +02:00
.gitattributes fate: add SCC test 2017-01-27 17:06:42 +01:00
.gitignore tools/python: add script to convert TensorFlow model (.pb) to native model (.model) 2019-07-01 10:23:47 -03:00
.mailmap mailmap: fix 3-address entries 2020-03-31 04:14:14 -05:00
.travis.yml Merge commit '899ee03088d55152a48830df0899887f055da1de' 2019-03-14 15:53:16 -03:00
Changelog avfilter/vf_scdet: add filter to detect scene change 2020-05-14 23:03:06 +08:00
configure avfilter/vf_scdet: add filter to detect scene change 2020-05-14 23:03:06 +08:00
CONTRIBUTING.md Add CONTRIBUTING.md 2016-09-18 10:02:13 +01:00
COPYING.GPLv2
COPYING.GPLv3
COPYING.LGPLv2.1
COPYING.LGPLv3
CREDITS
INSTALL.md INSTALL.md: Fix Markdown formatting 2019-01-31 10:29:16 -09:00
LICENSE.md avfilter/vf_geq: Relicense to LGPL 2019-12-28 11:20:48 +01:00
MAINTAINERS MAINTAINERS: Add myself to libopenh264enc 2020-05-06 19:12:00 +02:00
Makefile Makefile: Delete more created files when running "make distclean". 2020-03-11 11:43:01 +01:00
README.md Remove the ffserver program 2018-01-06 18:31:37 +00:00
RELEASE RELEASE: Update value for post 4.2 branch 2019-07-21 18:37:32 +02:00

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.