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• av_free crashes application randomly - FFMPEG C++

  12 mai 2013, par Spamdark

  I am trying to create a simple media-player for an introduction to the world of ffmpeg, the problem is that every time that I call av_freep(void*ptr) the application crashes.

  If I don't call av_freep I get a memory leak and the memory used by the program increases up to 1000MB (Already measured), here is the code :

  int16_t* audioBuffer=(int16_t*)av_malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE+FF_INPUT_BUFFER_PADDING_SIZE);
  
  
  
  if(!audioBuffer){
  
      MessageBox(0,"Error allocating in audioBuffer","Error: Mem",MB_ICONWARNING | MB_OK);
  
      return -1;
  
  }
  
  
  
  int sz = MEDIA->DecodeAudioFrame((void*)audioBuffer,0);
  
  
  
  Pa_WriteStream(MEDIA->output_stream,(int16_t*)audioBuffer,MEDIA->_audio_ccontext->frame_size);
  
  
  
  av_freep(audioBuffer);

  Here is my 'DecodeAudioFrame' function code :

  int WbMedia::DecodeAudioFrame(void *audio_buf, int buf_size){
  
  static AVFrame frame;
  
  static AVPacket pkt;
  
  static uint8_t *audio_pkt_data = NULL;
  
  static int audio_pkt_size = 0;
  
  
  
  int len1=0;
  
  
  
  for(;;){
  
      bool do_rt = false;
  
  
  
  
  
      while(audio_pkt_size > 0){
  
          int obt_frame = 0;
  
  
  
          len1 = avcodec_decode_audio4(_audio_ccontext,&frame,&obt_frame,&pkt);
  
          if(len1 < 0){
  
              audio_pkt_size = 0;
  
              break;
  
          }
  
  
  
          audio_pkt_data+=len1;
  
          audio_pkt_size-=len1;
  
  
  
          if(obt_frame){
  
              data_size = av_samples_get_buffer_size(frame.linesize,channel_count,sample_fr,_audio_ccontext->sample_fmt,1);
  
              memcpy(audio_buf,frame.data[0],data_size);
  
          }
  
  
  
          if(data_size < 0){
  
              continue;
  
          }
  
  
  
          if(pkt.data){
  
              av_free_packet(&pkt);
  
          }
  
          return data_size;
  
  
  
      }
  
  
  
      if(pkt.data){
  
          av_free_packet(&pkt);
  
      }
  
  
  
      if(do_rt){
  
          return data_size;
  
      }
  
  
  
      // Try to get a new packet
  
      if(!audio_packets.empty()){
  
          WaitForSingleObject(Queue_Audio_Mutex,INFINITE);
  
              pkt = audio_packets.front();
  
              audio_packets.pop();
  
          ReleaseMutex(Queue_Audio_Mutex);
  
  
  
          audio_pkt_size = pkt.size;
  
          audio_pkt_data = pkt.data;
  
      }else{
  
          return -1;
  
      }
  
  }
  
  return 0;
  
  }

  I need help with this issue, I don't know if it is a bug or what I need to do. What's happening there ? Why does it crashes on the av_freep call ? How can I fix it ?

  Thanks

• Piwik Analytics and becoming a Piwik Certified Professional

  10 juillet 2017, par Piwik Core Team — About

  Digital Analytics software

  Piwik Analytics is the leading open source digital analytics software, offering users around the world an opportunity to liberate their analytics. Most recently, they have introduced the Piwik Certified Professional certification exam which now allows users to become qualified in Piwik Analytics software on an individual level to gain a deeper understanding of Piwik. In this blog post I will guide you through the topics that are covered during the exam and provide you with advice on taking the official Piwik Certified Professional exam.

  

  Piwik certification exam

  Taking the exam will cost you a maximum investment of 60 minutes of your time, besides learning all materials of course. The exam consists of 55 multiple choice questions with four answers to choose from. The score needed to pass is 80% (44 questions answered correctly) and the cost is 50 USD total. An earned certificate is valid for 18 months, before these eighteen months are over a person should pass the exam again in order to retain the certified status.

  Learning topics

  The exam consists of two sections. The main section is focused on the Piwik Analytics software itself while the second part relates to digital analytics in general. All topics and content covered about Piwik Analytics is available through the official Piwik user guides. The second section tests your experience as a digital analyst, online marketer or any other function title in which you work with Piwik Analytics. In this case, the general digital analytics questions should be quite straightforward and easy to answer, and cover only a fraction of the total questions in the exam (around 10% with 5-7 general questions). An outline of all exam topics are listed below :

  • A Tour of Piwik
  • Track Goals and Measure Conversions
  • Event Tracking
  • Content Tracking
  • Ecommerce Analytics
  • Row Evolution – View and compare historical data
  • Segmentation – Compare segments of visitors
  • Visitors Maps – World, region, city
  • Real Time Visitor World Map
  • Real Time Analytics
  • The Visitor Profile
  • Site speed and Page speed
  • Site Search Tracking and Reporting
    
  • Transitions – Analyze the previous and following actions of your visitors for each page
  • Page Overlay
  • Custom Variables Analytics
  • Custom Dimensions
  • User ID
  • Annotating your data
  • Tracking Campaigns
  • URL Builder for Marketing Campaign Tracking

  The best way to prepare for the exam is read the entire Piwik user guides. You should definitely read the “Analytics Features” section since most questions of the Piwik Certified Professional – Digital Analytics exam that will be asked come from these sections. Furthermore you should be able to find your way around in Piwik at a basic level which means you know what the reports mean and where to find certain information. In addition, some basic knowledge regarding the settings is useful too. The exam is definitely not a technical implementation exam so no coding knowledge or any other deeply technical knowledge regarding Piwik is required.

  Finally, some general questions will be asked regarding digital analytics covering topics about KPI’s and the role of the analyst within an organization. While Piwik provides some links to articles by Avinash Kaushik covering these topics, you will not be able to learn these topics just by reading. When you have some experience with digital analytics you should be able to answer these general digital analytics questions with common sense and (even basic) experience as a digital analyst, analytics consultant, online marketer or any other related job whereby you work with Piwik.

  Taking the exam

  With 55 questions to be answered in 60 minutes the key to passing the exam is to keep moving. You have about 1 minute and 5 seconds to answer each question. This means that you should focus on the easiest questions first and return later to the questions that are a bit more challenging to answer. Keep an eye on the timer that will be displayed in the exam window. When the time expires or you click ‘Finish test’ your exam will end and be automatically submitted for review. Remember to first check all questions and answers before you click on the ‘Finish test’ button. If you click too soon and you still haven’t answered all questions, all unanswered questions will be marked as incorrect.

  During the test, no hard copy or online materials may be referenced. As you can imagine, it is almost impossible to check if users reference these kind of materials. However, be aware of the penalty system that is in place during the test. When a user leaves from the active test screen to another screen (i.e. a different browser tab) the screen turns red and provides a warning count when the user returns to the test screen again. You will have three warnings, after this your test will be submitted and graded as false. Furthermore, keep in mind you will have to do the test in one go and cannot pause and come back another time.

  Practice makes perfect

  Below I have included some example questions that could be asked during the exam. These questions do not necessarily represent how Piwik will test you on these topics.

  • What is the default report date that is selected by Piwik ?
  • Why would someone flatten a report in Piwik ?
  • Why would a user especially use the Page Overlay report ?
  • What are the three main Ecommerce interactions tracked with Piwik ?
  • What is an example of an anonymized IP address in Piwik ?

  Passing the Piwik Certified Professional – Digital Analytics exam

  Directly after submitting the exam you will receive a notification telling you whether or not you have passed the exam. If you pass, you will be able to download your personal certification right away. A report of your exam performance will also be available. This report lists the amount of correct answers and total questions by topic. The report with your exam performance is also available if you did not pass the exam. The certificate is valid for 18 months from the date of successful completion.

  Sometimes the difference between passing and failing can be a matter of how you interpret some of Piwik’s questions. There are several tricky questions included, so be sure to pay attention to detail on every question. If you fail, you may take the exam again. You will have to pay the 50 USD fee for each try, so do your best to pass it the first time.

  → Register to become a Piwik Certified Professional.

  We wish you the best of luck and happy analytics !

• FFMPEG library usage for own C++ project

  2 août 2017, par Chien-Yu Chan

  I would like to create my own project using FFMPEG to build a player, but creating a new file to include ffmpeg library seems not easy. I have configure the ffmpeg and make build.

  ./configure

  ./make

  The ffmpeg hello world program (myffmpeg.c) :

  #include <libavformat></libavformat>avformat.h>
  
  int main(int argc, char *argv[]) {
  
    av_register_all();
  
    return 0;
  
  }

  but it shows

  clang : warning : treating ’c’ input as ’c++’ when in C++ mode, this behavior is deprecated

  Undefined symbols for architecture x86_64 :

  "av_register_all()", referenced from :

  _main in myffmpeg-61ec1b.o

  ld : symbol(s) not found for architecture x86_64

  clang : error : linker command failed with exit code 1 (use -v to see invocation

  When I try to link the allformats.o file, which has av_register_all function inside. I got :

  clang : warning : treating ’c’ input as ’c++’ when in C++ mode, this behavior is deprecated
  Undefined symbols for architecture x86_64 :
  "_av_register_input_format", referenced from :
  _register_all in allformats.o
  "_av_register_output_format", referenced from :
  _register_all in allformats.o
  "_avcodec_register_all", referenced from :
  _register_all in allformats.o
  "_ff_a64_muxer", referenced from :
  _register_all in allformats.o

  ...

  "_ff_yuv4mpegpipe_muxer", referenced from :
  _register_all in allformats.o
  ld : symbol(s) not found for architecture x86_64
  clang : error : linker command failed with exit code 1 (use -v to see invocation)

  It should be my bad Makefile knowledge, could anyone give me some hint on how to call ffmpeg library functions ? Or even how to modify the Makefile to build my own program ? Thanks !

  *Update :
  It could be my compiling command problem, is it the way to compile ?

  g++ myffmpeg.c