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• FFMPEG Seeking with concat demuxer causes video & audio to be out of sync

  20 février 2023, par Garuuk

  I have a very simple use case that's driving me bananas.

  


  My problem and question :

  


  I'm using ffmpeg version 5.1.2 on a MacOS and i'm using ffmpeg seeking and concat demuxer to cut many 1 minute videos into 15 seconds chopped up over 12 clips where every clip is just 2 seconds from the same video (kind of like a mini teasers for the video). I would really like to not have to re-encode to make the video processing as fast as possible.

  


  First, I take each 1 minute video and cut it up into 12 clips (I do all this programmatically in python fwiw)

  


  ffmpeg -ss 0 -i input.mp4 -t 2 -c copy -y cut_1.mp4
ffmpeg -ss 4 -i input.mp4 -t 2 -c copy -y cut_2.mp4
ffmpeg -ss 8 -i input.mp4 -t 2 -c copy -y cut_3.mp4
...
...


  


  I then write all the output file names to my concat_manifest.txt

  


  file cut_1.mp4
file cut_2.mp4
...
...


  


  Then I run my concat command :

  


  ffmpeg -f concat -i concat_manifest.txt -c copy -y concat_video.mp4


  


  This works really fast but the audio and video at the stitch point get out of sync and sometimes the video just chokes & lags. It's mostly not a smooth experience.

  


  What I have tried :

  


  

  1. using the concat protocol with intermediate profiles : ffmpeg.org/wiki/Concatenate#demuxer

  


  2. Putting the -ss when I seek after the -i. This makes everything worse

  


  3. Playing around with different -ss values. This has some noticeable affects but it's not obvious why yet.

  


  4. I've also read from the ffmpeg resource regarding seeking and copying :

  


  


  Which leads me to believe that maybe because ffmpeg is using timestamps instead of frames, seeking isn't accurate using -ss when using the concat demuxer

  


  Is there a way to get concat demuxer cutting and concatenating the video where the audio is somewhat in sync with the video ?

  


  Thanks

  


  EDIT : I found an answer and i'll be posting the solution in the coming few days.

  


• Having trouble building FFmpeg using GNU make, Makefile:182 : /tests/Makefile : No such file or directory

  24 mai 2022, par Daedalus

  I'm having trouble building FFmpeg as a library to use in a project in vscode C++. I have no experience working with C/C++ libraries and would greatly appreciate any help. I've installed chocolatey and GNU make (GNU Make 4.3) with that, and the source code for FFmpeg. I cannot run make, as it tells me to do in the INSTALL.md file of the source code. I've been using command prompt to run the commands. Here are my errors :

  


  C:\ffmpeg>PowerShell ./configure

C:\ffmpeg>make
Makefile:182: /tests/Makefile: No such file or directory
make: *** No rule to make target '/tests/Makefile'.  Stop.

C:\ffmpeg>make install
Makefile:182: /tests/Makefile: No such file or directory
make: *** No rule to make target '/tests/Makefile'.  Stop.


  


  I've installed FFmpeg from github, and I can't find a working prebuilt library. I've tried different variations of the commands, with PowerShell and directories, but nothing has worked. This is INSTALL.md :

  


  


  Installing FFmpeg

  


  


  1. Type ./configure to create the configuration. A list of configure options is printed by running configure --help.

     


     configure can be launched from a directory different from the FFmpeg sources to build the objects out of tree. To do this, use an
absolute path when launching configure, e.g.
/ffmpegdir/ffmpeg/configure.

     


  


  2. Then type make to build FFmpeg. GNU Make 3.81 or later is required.

     


  


  3. Type make install to install all binaries and libraries you built.

     


  


  


  NOTICE

  


  

  • Non system dependencies (e.g. libx264, libvpx) are disabled by default.

  


  


  


  Any help would be greatly appreciated. Thanks in advance.

  


• Senior Software Engineer for Enterprise Analytics Platform

  28 janvier 2016, par Matthieu Aubry — Jobs

  We’re looking for a lead developer to work on Piwik Analytics core platform software. We have some exciting challenges to solve and need you !

  You’ll be working with both fellow employees and our open-source community. Piwik PRO staff lives in New Zealand, Europe (Poland, Germany) and in the U.S. We do the vast majority of our collaboration online.

  We are a small, flexible team, so when you come aboard, you will play an integral part in engineering. As a leader you’ll help us to prioritise work and grow our community. You’ll help to create a welcoming environment for new contributors and set an example with your development practices and communications skills. You will be working closely with our CTO to build a future for Piwik.

  Key Responsibilities

  • Strong competency coding in PHP and JavaScript.
  • Scaling existing backend system to handle ever increasing amounts of traffic and new product requirements.
  • Outstanding communication and collaboration skills.
  • Drive development and documentation of internal and external APIs (Piwik is an open platform).
  • Help make our development practices better and reduce friction from idea to deployment.
  • Mentor junior engineers and set the stage for personal growth.

  Minimum qualifications

  • 5+ years of experience in product development, security, usable interface design.
  • 5+ years experience building successful production software systems.
  • Strong competency in PHP5 and JavaScript application development.
  • Skill at writing tests and reviewing code.
  • Strong analytical skills.

  Location

  • Remote work position !
  • or you can join us in our office based in Wellington, New Zealand or in Wrocław, Poland.

  Benefits

  • Competitive salary.
  • Equity in Piwik PRO.
  • Remote work is possible.
  • Yearly meetup with the whole team abroad.
  • Be part of a successful open source company and community.
  • In our Wellington (NZ) and Wroclaw (PL) offices : snacks, coffee, nap room, Table football, Ping pong…
  • Regular events.
  • Great team of people.
  • Exciting projects.

  Learn more

  Learn more what it’s like to work on Piwik in our blog post

  About Piwik

  At Piwik and Piwik PRO we develop the leading open source web analytics platform, used by more than one million websites worldwide. Our vision is to help the world liberate their analytics data by building the best open alternative to Google Analytics.

  The Piwik platform collects, stores and processes a lot of information : hundreds of millions of data points each month. We create intuitive, simple and beautiful reports that delight our users.

  About Piwik PRO company

  At Piwik PRO we’re solving hard problems with simple solutions that make our users and customers happy. We practise agile methodology, test driven development and fast release cycles. Our backend is mostly built in modern PHP with a bit of Python. We use MySQL/MariaDB and Redis as data stores. Our frontends is built in JavaScript using AngularJS and jQuery. Our tools include Github, Travis CI, PhpStorm and Slack.

  As a Lead Software Developer for Piwik PRO, you will be writing open source code that will run on more than 200,000 servers and be used in 200+ countries and 50 languages !

  Apply online

  To apply for this position, please Apply online here. We look forward to receiving your applications !