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• How to extract small video chunk with ffmpeg ?

  3 décembre 2017, par Édouard Lopez

  I’m writing a script to split a video in multiple small files based on subtitles timing. Each chunk illustrated how to sign a word LSF (French Sign Language).

  However, some file are blank once extracted and when converted to webm they are 0kb.

  Timing data

  I extract the timing from a .ass file to get this kind of file

  0:00:01.01 0:00:04.07
  
  0:00:04.09 0:00:07.00
  
  0:00:07.00 0:00:10.36
  
  0:00:10.36 0:00:13.28

  First column is start_time, second is end_time

  Extraction

  extract_word_chunk() {
  
    ffmpeg \
  
      -i "$INPUT_FILE" \
  
      -ss "$start" \
  
      -to "$end" \
  
      -vcodec copy \
  
      -acodec copy \
  
      -loglevel error \
  
      "$chunk" < /dev/null
  
  }

  Conversion to webm

  convert_to_webm() {
  
    ffmpeg \
  
      -y \
  
      -i "$chunk" \
  
      -acodec libvorbis \
  
      -codec:v libvpx \
  
      -b:v 192k \
  
      -b:a 96k \
  
      -minrate 128k \
  
      -maxrate 256k \
  
      -bufsize 192k \
  
      -quality good \
  
      -cpu-used 2 \
  
      -deadline best \
  
      -loglevel error \
  
    "$chunk.webm" < /dev/null
  
  }

  Output

  # extract_word_chunk
  
  ffmpeg \
  
    -i 'assets/raw/partie 1: Apprendre 300 mots du quotidien en LSF.jauvert laura.mkv' \
  
    -ss 0:00:01.01 \
  
    -to 0:00:04.07 \
  
    -vcodec copy \
  
    -acodec copy \
  
    -loglevel error \
  
    assets/raw/0:00:01.01.mkv
  
  
  
  # convert_to_webm
  
  ffmpeg -y \
  
    -i assets/raw/0:00:01.01.mkv \
  
    -acodec libvorbis \
  
    -codec:v libvpx \
  
    -b:v 192k \
  
    -b:a 96k \
  
    -minrate 128k \
  
    -maxrate 256k \
  
    -bufsize 192k \
  
    -quality good \
  
    -cpu-used 2 \
  
    -deadline best \
  
    -loglevel error \
  
    assets/raw/0:00:01.01.mkv.webm

  Error

  [buffer @ 0x16d8be0] Unable to parse option value "-1" as pixel format
  
      Last message repeated 1 times
  
  [buffer @ 0x16d8be0] Error setting option pix_fmt to value -1.
  
  [graph 0 input from stream 0:0 @ 0x16e6fc0] Error applying options to the filter.

  Question

  Only some chunk are blank/empty.

  How do I prevent my video to be blank/empty ?

• We are hiring engineers to build an awesome product and platform used by millions of people

  16 février 2016, par Piwik Core Team — Uncategorized

  Are you ready for a new challenge ? Or maybe you know someone who is looking for a change ? We have some exciting problems to solve and are looking for senior developers to work with us and our community on our open source Piwik Analytics platform. Piwik is used by more than one million websites all over the world. It is deployed on more than 300.000 servers and some users track more than 1 billion actions per month.

  What is it like to work on Piwik ?

  We develop this software using modern PHP, MySQL, Redis, AngularJS and more. We provide several kind of APIs and a plugin architecture to allow developers to extend and change Piwik to their needs. However, we would not be Piwik if we stopped at this point ! We want to turn Piwik into an even more awesome product and platform.
  You can imagine there is a lot to do and many challenges to face !

  While one part is to always make Piwik scale better and to improve UI and UX, we also want to provide simple APIs to make the life of developers as pleasant as possible. We aim to solve things the right way and our thousands of unit, integration, system, JavaScript and screenshot tests help us to innovate and to not be afraid of change. We like clean code and constant improvements.

  The Piwik team lives in New Zealand and Europe (Germany). We do the vast majority of our collaboration online. Our values include being open, transparent and sharing knowledge. For this we use tools like GitHub and Slack to communicate and Quake servers to take our minds off complex challenges. We are a small, flexible team, so when you come aboard, you will play an integral part in engineering and have a big impact on the product loved by so many people. You’ll help to create a welcoming environment for new contributors and set an example with your development practices and communications skills.

  Apply now, or spread the word !

  If you have strong skills in PHP send us an email with your CV and tell us a little about yourself and your experience in engineering complex applications.

  Apply for a job here http://piwik.org/jobs/ and if you’re maybe not the right candidate, contribute to the project by sharing this blog post and by sending it to your friends !

• We are hiring engineers to build an awesome product and platform used by millions of people

  16 février 2016, par Piwik Core Team — Jobs

  Are you ready for a new challenge ? Or maybe you know someone who is looking for a change ? We have some exciting problems to solve and are looking for senior developers to work with us and our community on our open source Piwik Analytics platform. Piwik is used by more than one million websites all over the world. It is deployed on more than 300.000 servers and some users track more than 1 billion actions per month.

  What is it like to work on Piwik ?

  We develop this software using modern PHP, MySQL, Redis, AngularJS and more. We provide several kind of APIs and a plugin architecture to allow developers to extend and change Piwik to their needs. However, we would not be Piwik if we stopped at this point ! We want to turn Piwik into an even more awesome product and platform.
  You can imagine there is a lot to do and many challenges to face !

  While one part is to always make Piwik scale better and to improve UI and UX, we also want to provide simple APIs to make the life of developers as pleasant as possible. We aim to solve things the right way and our thousands of unit, integration, system, JavaScript and screenshot tests help us to innovate and to not be afraid of change. We like clean code and constant improvements.

  The Piwik team lives in New Zealand, Europe (Poland, Germany) and in the U.S. We do the vast majority of our collaboration online. Our values include being open, transparent and sharing knowledge. For this we use tools like GitHub and Slack to communicate and Quake servers to take our minds off complex challenges. We are a small, flexible team, so when you come aboard, you will play an integral part in engineering and have a big impact on the product loved by so many people. You’ll help to create a welcoming environment for new contributors and set an example with your development practices and communications skills.

  Apply now, or spread the word !

  If you have strong skills in PHP send us an email with your CV and tell us a little about yourself and your experience in engineering complex applications.

  Apply for a job here http://piwik.org/jobs/ and if you’re maybe not the right candidate, contribute to the project by sharing this blog post and by sending it to your friends !