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• how can I use the openCV FFMPEG video I/O rather than the DirectShow one in Windows ?

  2 mai 2012, par octi

  So I'm trying to write a video using the openCV videoWriter as such :

  writer=cv.CreateVideoWriter(path+"test_output.avi",-1,fps,(W,H),1)

  So instead of supplying the FOURCC I supplied -1 in order to see what codecs I have available.
  Result was Microsoft RLE, Microsoft Video 1, Intel YUV, and Uncompressed.

  The reason is that when configuring openCV using CMAKE for Visual Studio 10 x64, this is what I have in the video i/o :
  Video I/O : DirectShow

  Is there a way to switch this to FFMPEG ? I know the ffmpeg dll is present in \3dparty\ffmpeg.
  I looked for Cmake FFMPEG flags but found none whatsoever. The weird thing is in the CmakeLists.txt in the opencv root under the video section :

  if(UNIX AND NOT APPLE)
  
  <ffmpeg stuff="stuff">
  
  elseif(WIN32)
  
      status("  Video I/O:"        HAVE_VIDEOINPUT     THEN DirectShow ELSE NO)
  
  endif()
  
  </ffmpeg>

  So it seems to me that opencv automatically switched to DirectShow and gives no choice of using FFMpeg.
  Or rather can one upgrade Driectshow to support other formats such as Divx or h264 ?
  Any ideas ?

• Running command Subprocess python failed but the same exact command runs well in Terminal

  15 juillet 2023, par will

  As the title says : weird problem. I've been struggling to make this work for a whole day but to no avail. Any help would be deeply appreciated.

  


  # I've tried every one of the below path but still errors: Fontconfig error: Cannot load default config file: No such file: (null)

FONT_LOC = r'C\\:/Users/acer/AppData/Local/Microsoft/Windows/Fonts/jf-openhuninn-1.1.ttf'
FONT_LOC = 'C:/Users/acer/AppData/Local/Microsoft/Windows/Fonts/jf-openhuninn-1.1.ttf'
FONT_LOC = 'C://Users/acer/AppData/Local/Microsoft/Windows/Fonts/jf-openhuninn-1.1.ttf'


duration = '30
subtitle='abc'
comd = [
            "ffmpeg",
            "-f", "lavfi",
            "-i", "color=c=black:s=1280x720:d={duration}".format(duration=duration),
            "-vf", f'''drawtext=fontfile="{FONT_LOC}":text='{subtitle}':fontcolor=white:fontsize=24:x=(w-text_w)/2:y=(h-text_h)/2''',
            "-c:v", "libx264",
            "-t", duration,
            "-pix_fmt", "yuv420p",
            output_file+'.mp4'
            ]
print(' '.join(comd))
subprocess.run(comd, check=True, capture_output=True, text=True) # Failed


# The below command runs successfully in the terminal.
# ffmpeg -f lavfi -i color=c=black:s=1280x720:d=2.352000 -vf drawtext=fontfile="C\\://Users/acer/AppData/Local/Microsoft/Windows/Fonts/jf-openhuninn-1.1.ttf":text='abc':fontcolor=white:fontsize=24:x=(w-text_w)/2:y=(h-text_h)/2 -c:v libx264 -t 2.352000 -pix_fmt yuv420p output_Test-0004.mp3.mp4



  


  I expect the subprocess.run() would produce the same result. I've tried all versions of paths (different kind of escaping) but none of the aforementioned one worked.

  


• Difference between DirectShowSource() and FFmpegSource2() in AviSynth

  29 mars 2024, par MarianD

  For non .avi A/V sources (as .mp3, .mp4, etc.) there are (at least) 2 possibilities for reading those media files in AviSynth (in Windows) :

  



  

  • The built-in media filter DirectShowSource(), using Microsoft's DirectShow media architecture.

  


  • The AviSynth Plugin FFmpegSource2() alias FFMS2() using FFmpeg and nothing else.

  


  



  What are advantages and disadvantages of them ?
  
Which is more reliable, frame / sample accurate, etc.?