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• how the packuswb instruction works ? (in low level bit operation)

  17 avril 2019, par MaikonNascimento

  Studying ffmpeg convertion from yuv to rgb , I came across the equation being implemented in assembly, yuv2rgb_template.c located in ffmpeg/libswscale/x86.

  I want to know how the instruction packuswb works ? Google says it :

  Converts 4 signed word integers from mm and 4 signed word integers from mm/m64 into 8 unsigned byte integers in mm using unsigned saturation.

      DEST[7:0] ← SaturateSignedWordToUnsignedByte DEST[15:0];
  
      DEST[15:8] ← SaturateSignedWordToUnsignedByte DEST[31:16];
  
      DEST[23:16] ← SaturateSignedWordToUnsignedByte DEST[47:32];
  
      DEST[31:24] ← SaturateSignedWordToUnsignedByte DEST[63:48];
  
      DEST[39:32] ← SaturateSignedWordToUnsignedByte SRC[15:0];
  
      DEST[47:40] ← SaturateSignedWordToUnsignedByte SRC[31:16];
  
      DEST[55:48] ← SaturateSignedWordToUnsignedByte SRC[47:32];
  
      DEST[63:56] ← SaturateSignedWordToUnsignedByte SRC[63:48];

  Since I dont know Assembly x86, it is even hard to simulate it or debug the current code.

  I want to know how they fit 16 bits in 8 bits ?

• FFMPEG - Palettegen for animations is not working

  18 juillet 2018, par deanhodges

  I have a script taken from the correct answer at https://superuser.com/questions/1002562/convert-multiple-images-to-a-gif-with-cross-dissolve, but I am getting no results.

  Even copying the code word for word does not work for me.

  However, if I run $ffmpeg = shell_exec("ffmpeg -i images/image001.jpg -vf palettegen palette_test.png"); on a single image, it works fine. But because I need it for an animation, I need to create a pallete for all images.

  Unless of course, on each image in the GIF sequence I can load a new palette ?

  $q = "ffmpeg -f image2 -framerate 0.5 -i ../view/client/files/".$dir."/%*.jpg -i palettePro.png -lavfi paletteuse -y .." . $save_path . '/' . $filename . " -report";

• Strange error with ffmpeg and unoconv in python script

  27 mai 2015, par Avery Ripoll Crocker

  I am creating a python script that can be used by other people to convert files. However when I use this script I keep getting a weird error when I run the subprocess for unoconv, this error is :

  Traceback (most recent call last):
  
    File "conversion.py", line 15, in <module>
  
      check_call(["unoconv", "-f", Fileextension, filename])
  
    File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
  
      raise CalledProcessError(retcode, cmd)
  
  subprocess.CalledProcessError: Command '['unoconv', '-f', '.pdf', 'journal.doc']' returned non-zero exit status 1
  
  </module>

  I have looked through various resources for this, but the one answer I have been receiving is that I must have set up the unoconv line incorrectly. I have checked several times that the code is correct, and it is. The other peculiar thing is that my code for ffmpeg works. Does anybody have an idea as to why this happens.

  Here is my program :

  print "If at any point you wish to quit the program hit Ctrl + C"
  
  
  
  filetype = raw_input("What kind of file would you like to convert? Audio, Image, Video or Document: ")
  
  
  
  if filetype == "Document":
  
     path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
  
     os.chdir(path[1:-2])
  
     filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
  
     Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .txt: ")
  
     from subprocess import check_call
  
     check_call(["unoconv", "-f", Fileextension, filename])
  
  
  
  elif filetype == "Audio":
  
     path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
  
     os.chdir(path[1:-2])
  
     filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
  
     Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .mp3: ")
  
     body, ext = os.path.splitext("filename")
  
     from subprocess import check_call
  
     check_call(["ffmpeg" ,"-i", filename, body + Fileextension])
  
  
  
  elif filetype == "Video":
  
     path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
  
     os.chdir(path[1:-2])
  
     filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
  
     Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .mp4: ")
  
     body, ext = os.path.splitext("filename")
  
     from subprocess import check_call
  
     check_call(["ffmpeg" ,"-i", filename, body + Fileextension])
  
  
  
  elif filetype == "Image":
  
     path = raw_input("Please drag and drop the directory in which the file is stored into the terminal:")
  
     os.chdir(path[1:-2])
  
     filename = raw_input("Please enter the name of the file you would like to convert, including the file-type. e.g. test.txt, however please do make sure that the file-name does not have any spaces:")
  
     Fileextension = raw_input("What filetype would you like the program to convert your file to. E.g. .Jpeg: ")
  
     body, ext = os.path.splitext("filename")
  
     from subprocess import check_call    
  
     check_call(["ffmpeg" ,"-i", filename, body + Fileextension])