Sur d’autres sites (6475)

• Improper use of system() call ?

  28 mai 2013, par Dima1982

  I have a particle system program that generates a .dat file with particle coordinates in every iteration. The end goal is to run the program multiple times via a script with different parameters. So, I am trying to setup my program in a way that, for every run, all relevant data are going to be stored in a folder.

  What I do is to generate PNGs from the .dat files with Gnuplot, call ffmpeg to create a video out of the PNGs, use WinRAR to compress the .dat files and finally clean up, by deleting all the intermediate files. This works, when I do it in the working directory.

  Now I try to create a new directory and do the same stuff in there. My code :

  // Load the proper library to use chdir() function
  
  #ifdef _WIN32
  
  #include 
  
  #elif defined __linux__ || defined __APPLE__&&__MACH__
  
  #include 
  
  #endif
  
  
  
  // Make output directory and change working directory to new directory
  
      ostringstream dirCommand;
  
      dirCommand << "mkdir " << folderName_str;
  
      system(dirCommand.str().c_str());
  
      const char* test  = folderName_str.c_str();
  
      #ifdef _WIN32
  
          if(_chdir(test))
  
          {
  
              printf( "Unable to locate the directory: %s\n",test);
  
              return;
  
          }
  
      #elif defined __linux__ || defined __APPLE__&&__MACH__
  
          if(chdir(test))
  
          {
  
              printf( "Unable to locate the directory: %s\n",test);
  
              return;
  
          }
  
      #endif
  
          else
  
              printf("Created output directory...\n");

  Already for this part, I know that there are going to be objections. I have looked extensively on SO and many people favor SetCurrentDirectory() for Windows, or they are skeptical about using system(). In my defense, I am a novice programmer and my knowledge is really limited...

  Now, when I try to make the video with FFMpeg and then rar/tar my files :

  // Make video
  
          std::cout << "Generating Video..." << endl;
  
          ostringstream command;
  
          command << "ffmpeg -f image2 -r 1/0.1 -i output_%01d.png -vcodec mpeg4 " << videoName_str << ".avi -loglevel quiet";
  
          std::system(command.str().c_str());
  
  
  
          // Clean Up!
  
          std::cout << "Cleaning up!" << endl;
  
          ostringstream command2;
  
          #ifdef _WIN32
  
              command2 << "rar -inul a " << videoName_str << ".rar *.dat settings.gp loadfile.gp";
  
          #elif defined __linux__ || defined __APPLE__&&__MACH__
  
              command2 << "tar cf " << videoName_str << ".tar *.dat settings.gp loadfile.gp";
  
          #endif
  
          std::system(command2.str().c_str());

  I get very different behaviors in Win/ Linux.

  Win 7 x64, Visual Studio 2010/12

  In windows, the folder is created. The .dat files are generated correctly and gnuplot plots the PNGs as well. When ffmpeg is called, nothing happens. No error message from FFMpeg or anything. The same goes for WinRAR. Maybe, for the last thing, I can use the command line utility of 7z which is free !

  Linux Mint 14 x64, Qt 4.8.1

  Strangely enough, the behavior is inverted from that of Windows. As soon as the dir is changed, only the first .dat file is generated. It is as if every subsequent call I make to fprintf() for my file generation does not work, or gets lost somewhere. Gnuplot works, as do ffmpeg and tar !!

  I am really perplexed. Any help, would be really appreciated.

• Python Matplotlib Basemap animation with FFMpegwriter stops after 820 Frames ?

  5 août 2013, par cpaulik

  If I run the following code it just stops after 820 Frames. I tested this on both a Ubuntu 12.04 VM and on Linux Mint 15. Unfortunately there is no error message. The program just hangs after printing 2012-06-02T16:54:00

  import os, sys
  
  import matplotlib.pyplot as plt
  
  from mpl_toolkits.basemap import Basemap
  
  import matplotlib.animation as animation
  
  from datetime import datetime,timedelta
  
  
  
  def animation_test(start,end,fps=10,save_path='/home/username/animation_test/',\
  
  save_name="test.mp4",dpi=80):
  
  
  
      step = timedelta(minutes = 3)
  
  
  
      current = start
  
  
  
      dates =[]
  
  
  
      frame = 0
  
  
  
      while current <=end:
  
          dates.append(current)
  
          current += step
  
  
  
      fig = plt.figure(figsize=(16,9),facecolor='k',edgecolor='k')
  
      ax = fig.add_subplot(111)
  
  
  
      metadata = dict(title='Movie Test', artist='Matplotlib',
  
              comment='Movie support!')
  
      writer = animation.FFMpegWriter(fps=fps, metadata=metadata,bitrate=20000)
  
  
  
      direction = -0.5
  
      lat_current = 0
  
      lon_current = 0
  
  
  
      with writer.saving(fig,os.path.join(save_path,save_name),dpi):
  
  
  
          for current in dates:
  
  
  
              ax.cla()
  
              if direction > 0 and lat_current > 40 or \
  
                     direction < 0 and lat_current < -40:
  
                      direction = - direction
  
  
  
              lat_current = lat_current + direction
  
              lon_current = lon_current - 0.75
  
              if lon_current < -180 :
  
                  lon_current += 360
  
              basem = Basemap(projection='ortho', lat_0=lat_current, lon_0=lon_current, resolution='l',ax=ax)
  
              basem.drawcoastlines()
  
  
  
              #plt.show()
  
  
  
              plt.savefig(os.path.join(save_path, 'frame%d.png'%frame),
  
                  dpi=dpi,facecolor='w',edgecolor='k')
  
  
  
              writer.grab_frame()
  
              frame += 1
  
              print current.isoformat()
  
  
  
  start = datetime.now()
  
  animation_test(datetime(2012,6,1,0,0,0),datetime(2012,6,4,0,0,0),fps=10,dpi=80)
  
  print datetime.now() - start

  To explain the code a little bit :
  I want to make an animation of satellite data which comes in small 3 minute files and show it on a rotating globe. This is why I chose to make the loop in the following example code step through the animation in 3 minute steps. I just removed the reading and plotting of the satellite data in order to make the code executable by anyone.

  When I removed basemap from the program and just plotted a scatterplot of random data the program ran all the way through.

  I'm not sure but I don't think that it is a memory issue since my RAM is only utilized approx. 20% while the program is running.

  Thanks for any help in getting to the bottom of this.

• How to use android ndk r9b to compile FFMPEG for Android

  27 août 2015, par user3032481

  I want to design an Android app which can play and edit video by FFMPEG commands.
  But I don’t know how to use FFMPEG on Android. I have tried many methods searched from Google, but they are too old to implement.
  Now, the newest version of FFMPEG is 2.1.1 and the Android-NDK’s version is r9b. My operating system is Linux mint 15.
  How can I use eclipse IDE on my OS to implement an Android app which has FFMPEG’s newest decoder and encoder ?