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• FFmpeg avutil.lib unresolved external symbol

  2 août 2022, par Sere

  i'm trying to use FFmpeg with visual sudio 2022 .NET 6 through an MSVC project.
I followed this tutorial : https://www.youtube.com/watch?v=qMNr1Su-nR8&ab_channel=HakanSoyalp.
I mean I have configureg Include (.h) file, library (.lib) files and dynamic (.dll) file copied into bin folder.
If I call for example the avformat_alloc_context() method inside the avformat.lib all work rightly, if I call for example av_file_map(...) inside the avutil.lib the compiler give me an error :
LNK2019 unresolved external symbol "int __cdecl av_file_map ...
But the avutil.lib is linked !!!
The same happen if I call other methods inside avutil.lib module.

  


  Thanks for help...

  


  Code :

  


  extern "C"&#xA;{&#xA;    #include <libavformat></libavformat>avformat.h>&#xA;    #include <libavutil></libavutil>file.h> // av_file_map&#xA;}&#xA;&#xA;int ConvertJPEGtoNALs(int argc, char* argv[])&#xA;{&#xA;    AVFormatContext* fmt_ctx = NULL;&#xA;    AVIOContext* avio_ctx = NULL;&#xA;    uint8_t* buffer = NULL, * avio_ctx_buffer = NULL;&#xA;    size_t buffer_size, avio_ctx_buffer_size = 4096;&#xA;    char* input_filename = NULL;&#xA;    int ret = 0;&#xA;    struct buffer_data bd = { 0 };&#xA;    if (argc != 2) {&#xA;        fprintf(stderr, "usage: %s input_file\n"&#xA;            "API example program to show how to read from a custom buffer "&#xA;            "accessed through AVIOContext.\n", argv[0]);&#xA;        return 1;&#xA;    }&#xA;    input_filename = argv[1];&#xA;    /* register codecs and formats and other lavf/lavc components*/&#xA;    //av_register_all();    //!deprecated&#xA;    /* slurp file content into buffer */&#xA;    ret = av_file_map(input_filename, &amp;buffer, &amp;buffer_size, 0, NULL);&#xA;    /* fill opaque structure used by the AVIOContext read callback */&#xA;    bd.ptr = buffer;&#xA;    bd.size = buffer_size; ???&#xA;    if (!(fmt_ctx = avformat_alloc_context())) {&#xA;        ret = AVERROR(ENOMEM);&#xA;        goto end;&#xA;    }&#xA;    //... to be continue ...&#xA;}&#xA;

  


• OpenCV Python, reading video from named-pipe

  29 février 2020, par BlueNut

  I am trying to achieve results as shown on the video (Method 3 using netcat) https://www.youtube.com/watch?v=sYGdge3T30o
  It is to stream video from raspberry pi to PC and process it using openCV and python.

  I use command

  raspivid -vf -n -w 640 -h 480 -o - -t 0 -b 2000000 | nc 192.168.1.137 8000

  to stream the video to my PC and then on the PC I created name pipe ’fifo’ and redirected the output

  nc -l -p 8000 -v > fifo

  then i am trying to read the pipe and display the result in the python script

  import cv2
  
  import subprocess as sp
  
  import numpy
  
  
  
  FFMPEG_BIN = "ffmpeg.exe"
  
  command = [ FFMPEG_BIN,
  
          '-i', 'fifo',             # fifo is the named pipe
  
          '-pix_fmt', 'bgr24',      # opencv requires bgr24 pixel format.
  
          '-vcodec', 'rawvideo',
  
          '-an','-sn',              # we want to disable audio processing (there is no audio)
  
          '-f', 'image2pipe', '-']    
  
  pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)
  
  
  
  while True:
  
      # Capture frame-by-frame
  
      raw_image = pipe.stdout.read(640*480*3)
  
      # transform the byte read into a numpy array
  
      image =  numpy.frombuffer(raw_image, dtype='uint8')
  
      image = image.reshape((480,640,3))          # Notice how height is specified first and then width
  
      if image is not None:
  
          cv2.imshow('Video', image)
  
  
  
      if cv2.waitKey(1) & 0xFF == ord('q'):
  
          break
  
      pipe.stdout.flush()
  
  
  
  cv2.destroyAllWindows()

  But I got this error :

  Traceback (most recent call last):
  
    File "C:\Users\Nick\Desktop\python video stream\stream.py", line 19, in <module>
  
      image = image.reshape((480,640,3))          # Notice how height is specified first and then width
  
  ValueError: cannot reshape array of size 0 into shape (480,640,3)
  
  </module>

  It seems that the numpy array is empty, so any ideas to fix this ?

• Install Piwik with 1-click using Installatron

  28 mars 2013, par Piwik team — Community

  We are proud to announce that Piwik Analytics is now available as one click install from Installatron !

  Installatron is a one-click web application installer that enables Piwik and other top web applications to be instantly installed and effortlessly managed. Get Piwik up and running on your website in seconds and discover just how easy Installatron makes it to manage web applications. Piwik installations managed by Installatron can updated (manually or automated), cloned, backed up and restored, edited to change installation parameters, and more.

  

  Many web hosting providers provide Installatron through their web hosting control panel. If Installatron is not available from your provider, you can use Installatron directly from Installatron.com.

  To install Piwik through your web hosting provider’s control panel (if available) :

  • Login to your web host’s control panel,
  • navigate to “Installatron”, click “Piwik”, and choose the “Install this application” option.
  • Change any of the install prompts to customize the install. For
    example, you can choose a different default language for Piwik.
  • Click the “Install” button to begin the installation process. You
    will be redirect to a progress page where you can watch as Piwik is
    installed within a few seconds to your website.

  

  You can also install Piwik directly from Installatron.com, by navigating to Piwik @Installatron and choose the “Install this application” option. After filling in your FTP and Mysql information, you will be redirect to a progress page where you can watch as Piwik is installed within a few seconds to your website. After the installation, you may wish to change your FTP, Mysql password.

  If you experience any problems or want to share your experience using Piwik and Installatron together, email the Installatron team at : feedback (at) installatron.com