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• Python animation saves only one single frame

  5 octobre 2015, par JohnND

  I’m trying to save a python animation as a video file. The animation itself works fine with show(). But when I use save() I get a video file containing only one frame which stays on for the duration of the video. The duration itself seems correct (2 minutes).
  Here’s my script, it gets some data from files that are read by custom functions then use the data to make an animation. I’ve tried various alternatives like specifying ffmpeg as writer or using Agg as backend. So far it all gives the same result. Is there some obvious misuse of the animation module ?

  #!/usr/bin/env python
  
  
  
  import sys
  
  import os
  
  import matplotlib
  
  #matplotlib.use("Agg")
  
  import numpy as np
  
  import math as mh
  
  from pylab import *
  
  from matplotlib import animation as animation
  
  #plt.rcParams['animation.ffmpeg_path'] = '/usr/bin/ffmpeg'
  
  
  
  sys.path.append('/home/jseverin/bin/myPythonScripts/')
  
  import temp_profile_v4
  
  
  
  ##########################################################################
  
  #                          Function definition                           #
  
  ##########################################################################
  
  
  
  
  
  ##########################################################################
  
  #                                  Main                                  #
  
  ##########################################################################
  
  
  
  def main(args):
  
      log_file = args[1]
  
  
  
      lz, coords, instant_profiles, fig1, Nlayers = temp_profile_v4.main(["temp_profile_v4.py", "-i", log_file])
  
      close(fig1)
  
  
  
      # Layer thickness in angstroms
  
      thickA = lz/Nlayers
  
      thickA2 = thickA/2
  
  
  
  
  
      # We need to slice the array
  
      # We choose the width of the exclusion area as a fraction of the source/sink width
  
      fract = 1.0
  
      safeDist = fract*thickA
  
      #sliced_coords, sliced_temps = slice_prof(safeDist, thickA2, lz, slice_coords, slice_temps)
  
  
  
      Nframes = int(len(instant_profiles)/2)
  
  
  
      # Plot setup
  
  
  
      fig = figure(figsize=(12,8.5)) # initialise la figure
  
      line, = plot([],[], '-', linewidth=1.5, label = "T(z)")
  
  
  
      ymax = 0
  
      for prof in instant_profiles :
  
          dummy = max(prof)
  
          if dummy > ymax :
  
              ymax = dummy
  
  
  
      ymin = 999999999
  
      for prof in instant_profiles :
  
          dummy = min(prof)
  
          if dummy < ymin :
  
              ymin = dummy
  
  
  
      xlim([-0.1, lz])
  
      ylim([ymin, ymax])
  
      xlabel(r'z ($\AA$)', fontsize=14)
  
      ylabel('Temperature (K)', fontsize=14)
  
  
  
      # Show source and sink on graph
  
      axvspan(lz/4-thickA2, lz/4+thickA2, alpha=0.2, color='black', label=r"source/sink (a = %d $\AA$)" % int(round(thickA)))
  
      axvspan(3*lz/4-thickA2, 3*lz/4+thickA2, alpha=0.2, color='black')
  
      axvline(x=lz/4 + thickA2 + safeDist, linestyle='--', color='k')
  
      axvline(x=3*lz/4 - thickA2 - safeDist, linestyle='--', color='k')
  
  
  
      # fonction a definir quand blit=True
  
      # cree l'arriere de l'animation qui sera present sur chaque image
  
      def init():
  
          line.set_data([],[])
  
          return line,
  
  
  
      def animate(i): 
  
          step = 2*i
  
          line.set_data(coords, instant_profiles[step])
  
          return line,
  
  
  
      ani = animation.FuncAnimation(fig, animate, init_func=init, frames=Nframes, blit=True, interval=20, repeat=False)
  
  
  
      show()
  
  
  
      #FFwriter = animation.FFMpegWriter()
  
      #ani.save('dynamic_profile.mp4', writer = 'ffmpeg')
  
  
  
      # Set up formatting for the movie files
  
      #Writer = animation.writers['ffmpeg']
  
      #writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)
  
      #ani.save('animation.mp4', writer=writer)
  
  
  
      ani.save('animation.mp4', fps=15)
  
  
  
  # End main
  
  
  
  if __name__=="__main__":
  
      main(sys.argv)

• Replace Special Characters In Batch-File Variable Feeding ffmpeg program

  14 janvier 2019, par whereswaller

  I am attempting to write a batch-file that leverages ffmpeg.exe to convert all files in a folder structure to mp3 format (specifically 128 KBps).

  My batch-file is presently unable to process filenames (constructed by concatenating the %_SOURCE% and %%~F variables) containing certain special characters generating the following errors :

  No such file or directory

  • … ellipsis sign
  • – en dash
  • — em dash
  • − minus sign

  Invalid argument

  • ‘ and ’ curved single quotation marks
  • “ and ” curved double quotation marks

  Invalid argument (yet sometimes passes depending on where symbol is in the filename, for example, seems to work if placed between the n and t of Dont in C:\Users\Test\Documents\Input\Peter Bjorn And John - I Know You Dont Love Me.mp3)

  • - hyphen
  • ! exclamation mark
  • ~ tilde
  • ' non-curved single quotation mark
  • = equals sign
  • + plus sign
  • % percentage sign
  • ( open bracket

  How can I modify my batch-file script so that the %%~F variable escapes these characters correctly ?

  Example current filename input : C:\Users\Test\Documents\Input\Peter Bjorn And John - I Know You Don't Love Me.mp3

  Example desired filename input : C:\Users\Test\Documents\Input\Peter Bjorn And John - I Know You Don"^'"t Love Me.mp3

  Script (see line beginning C:\ffmpeg\bin\ffmpeg.exe) :

  @echo off
  
  setlocal EnableExtensions DisableDelayedExpansion
  
  
  
  rem // Define constants here:
  
  set "_SOURCE=C:\Users\Test\Documents\Input" & rem // (absolute source path)
  
  set "_TARGET=C:\Users\Test\Documents\Output"  & rem // (absolute target path)
  
  set "_PATTERN=*.*" & rem // (pure file pattern for input files)
  
  set "_FILEEXT=.mp3"   & rem // (pure file extension of output files)
  
  
  
  pushd "%_TARGET%" || exit /B 1
  
  for /F "delims=" %%F in ('
  
      cd /D "%_SOURCE%" ^&^& ^(rem/ list but do not copy: ^
  
          ^& xcopy /L /S /Y /I ".\%_PATTERN%" "%_TARGET%" ^
  
          ^| find ".\" ^& rem/ remove summary line;
  
      ^)
  
  ') do (
  
      2> nul mkdir "%%~dpF."
  
  
  
      rem // Set up the correct `ffmpeg` command line here:
  
      set "FFREPORT=file=C\:\\Users\\Test\\Documents\\Output\\ffreport-%%~F.log:level=32"
  
      "C:\ffmpeg\bin\ffmpeg.exe" -report -n -i "%_SOURCE%\%%~F" -vn -c:a libmp3lame -b:a 128k "%%~dpnF%_FILEEXT%"
  
      if not errorlevel 1  if exist "%%~dpnF%_FILEEXT%" del /f /q "%_SOURCE%\%%~F"
  
  
  
  )
  
  popd
  
  
  
  endlocal
  
  pause

• Unable to Create Videos on OpenCV (VideoCapture Class) for Mac OS

  17 janvier 2017, par MBT

  Hi Programming Guru’s,

  I am using Mac OS 10.12.1 with OpenCV 3.0. I tried to capture live videos from webcam and try to save it as a video file. I know that many have tried out this but there were not a clear solution specifically to Mac OS.

  Some have said to use FFMPEG in order to do in Mac OS, other have mentioned to try with different codec in CV_FOURCC. I tried both and I was not able to get the desired results. So I am bit confused by reading all the stuffs.

  Below is a C++ code :

  #include <opencv2></opencv2>opencv.hpp>
  
  #include <iostream>
  
  #include 
  
  using namespace cv;
  
  using namespace std;
  
  int main(int, char**)
  
  {
  
      Mat src;
  
      // use default camera as video source
  
      VideoCapture cap(0);
  
      // check if we succeeded
  
      if (!cap.isOpened()) {
  
          cerr &lt;&lt; "ERROR! Unable to open camera\n";
  
          return -1;
  
      }
  
      // get one frame from camera to know frame size and type
  
      cap >> src;
  
      // check if we succeeded
  
      if (src.empty()) {
  
          cerr &lt;&lt; "ERROR! blank frame grabbed\n";
  
          return -1;
  
      }
  
      bool isColor = (src.type() == CV_8UC3);
  
      //--- INITIALIZE VIDEOWRITER
  
      VideoWriter writer;
  
      int codec = CV_FOURCC('H', '2', '6', '4');  // select desired codec (must be available at runtime)
  
      double fps = 25.0;                          // framerate of the created video stream
  
      string filename = "./live.avi";             // name of the output video file
  
      writer.open(filename, codec, fps, src.size(), isColor);
  
      // check if we succeeded
  
      if (!writer.isOpened()) {
  
          cerr &lt;&lt; "Could not open the output video file for write\n";
  
          return -1;
  
      }
  
      //--- GRAB AND WRITE LOOP
  
      cout &lt;&lt; "Writing videofile: " &lt;&lt; filename &lt;&lt; endl
  
           &lt;&lt; "Press any key to terminate" &lt;&lt; endl;
  
      for (;;)
  
      {
  
          // check if we succeeded
  
          if (!cap.read(src)) {
  
              cerr &lt;&lt; "ERROR! blank frame grabbed\n";
  
              break;
  
          }
  
          // encode the frame into the videofile stream
  
          writer.write(src);
  
          // show live and wait for a key with timeout long enough to show images
  
          imshow("Live", src);
  
          if (waitKey(5) >= 0)
  
              break;
  
      }
  
      // the videofile will be closed and released automatically in VideoWriter destructor
  
      return 0;
  
  }
  
  </iostream>

  When I run the above code, I see a video is created with only a single frame.

  I tried with Many Video CODEC like ’A’,’V’,’C’,’1’, ’M’,’P’,’4’,’V’, ’H’,’2’,’6’,’4’or ’X’,’2’,’6’,’4’. But not works with MAC.

  It would be really wonderful if you can suggest me the correct way to solve this issue.

  Thank You