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• avcodec/vorbisenc : Combine codebooks, avoid relocations

  7 mai 2021, par Andreas Rheinhardt

  avcodec/vorbisenc : Combine codebooks, avoid relocations
  The Vorbis encoder has an array of a structure containing all
  
  the ingredients for a codebook ; this includes a pointer to
  
  the actual codebook and some even have a pointer to an array
  
  containing quant values. Each of these real codebooks is
  
  an array of its own.
  
  These pointers lead to relocations and therefore the array will
  
  be placed in .data.rel.ro and not in .rodata.
  This commit avoids the pointers altogether by combining all the actual
  
  codebooks into one big array ; the actual codebooks are now accessed
  
  consecutively by incrementing the pointer used to access them by the
  
  length of the actual codebook that has just been dealt with (said length
  
  is contained in the structure describing the codebook). There is
  
  no downside to this given that these codebooks are already only used
  
  once during init.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/vorbis_enc_data.h
  • [DH] libavcodec/vorbisenc.c

• avcodec/svq1enc : Use unsigned for parameter >= 0 to workaround GCC bug

  10 juillet 2022, par Andreas Rheinhardt

  avcodec/svq1enc : Use unsigned for parameter >= 0 to workaround GCC bug
  encode_block() in svq1enc.c looks like the following :
  static int encode_block(int block[7][256], int level)
  
  
  
      int best_score = 0 ;
  
      for (unsigned x = 0 ; x < level ; x++) 
  
          int v = block[1][x] ;
  
          block[level][x] = 0 ;
  
          best_score      += v * v ;
  
      
      if (level > 0 && best_score > 64) 
  
          int score = 0 ;
  
          score += encode_block(block, level - 1) ;
  
          score += encode_block(block, level - 1) ;
          if (score < best_score) 
  
              best_score = score ;
  
          
  
      
      return best_score ;
  
  
  When called from outside of encode_block(), it is always called with
  
  level == 5.
  This triggers a bug [1] in GCC : On -O3, it creates eight clones of
  
  encode_block with different values of level inlined into it. The clones
  
  with negative values are of course useless*, but they also lead to
  
   Warray-bounds warnings, because they access block[-1].
  This has been mitigated in GCC 12 : It no longer creates clones
  
  for parameters that it knows are impossible. Somehow switching levels
  
  to unsigned makes GCC know this. Therefore this commit does this.
  
  (For GCC 11, this changes the warning to "array subscript 4294967295 is
  
  above array bounds" from "array subscript -1 is below array bounds".)
  [1] : https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102513
  * : These clones can actually be discarded when compiling with
  
   ffunction-sections.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/svq1enc.c

• 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 !