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• Script for video to j2k conversion not working

  8 février 2015, par Subhajit

  I am trying to convert a 2k prores file to j2c image sequence so can I wrap them in mxf file. I am trying to bypass intermediate dpx or tiff conversion.
  But with my limited programming knowledge I am not getting success. Can u plz guide me what is wrong with my code.

  import subprocess as sp
  
  
  
  import subprocess as sp
  
  
  
  import sys
  
  
  
  import numpy
  
  
  
  
  
  FFMPEG = "ffmpeg"
  
  
  
  IMAGEMAGICK = "convert"
  
  
  
  COLOUR_MATRIX = "0.4124564,0.3575761,0.1804375,0.2126729,0.7151522,0.0721750,0.0193339,0.1191920,0.9503041"
  
  
  
  infile = sys.argv[1]
  
  fps = sys.argv[2]
  
  outfile = ('0'.zfill(8))
  
  
  
  
  
  to_dpx = [FFMPEG,'-i',infile,'-f','image2pipe','-pix_fmt','rgb24','-c:v','dpx','-r',fps,'-']
  
  to_j2k = [IMAGEMAGICK,'-','-alpha','off','-depth','12','-gamma','0.454545','-recolor',COLOUR_MATRIX,'-evaluate','multiply','0.9166',str(outfile)+'.j2c']
  
  
  
  pipe = sp.Popen(to_dpx,stdout = sp.PIPE, bufsize = 10**8)
  
  
  
  
  
  while(pipe.pull() is NONE):
  
  raw_image = pipe.stdout.read(2048*872*3)
  
  image = numpy.fromstring(raw_image,dtype = 'uint8')
  
  image = image.reshape((2048,872,3))
  
  pipe = sp.Popen(to_j2k,stdin = sp.PIPE,stderr = sp.pipe)
  
  outfile = int(outfile) + 1

  ERROR REPORTS :
  Reported by python :

  $python AurOchs_dc_compiler.py Sample2Kprores.mov 24
  
  Traceback (most recent call last):
  
  File "AurOchs_dc_compiler.py", line 17, in <module>
  
  pipe = sp.Popen(to_dpx,stdout = sp.PIPE, bufsize = 100**8)
  
  File "/usr/lib/python2.7/subprocess.py", line 739, in __init__
  
  self.stdout = os.fdopen(c2pread, 'rb', bufsize)
  
  OverflowError: signed integer is greater than maximum
  
  </module>

  Error messages by ffmpeg :

  Stream mapping:
  
  Stream #0:0 -> #0:0 (prores (native) -> dpx (native))
  
  Press [q] to stop, [?] for help
  
  av_interleaved_write_frame(): Broken pipe
  
  frame= 1 fps=0.0 q=-1.0 Lsize= 5234kB time=00:00:00.04 bitrate=1028964.3kbits/s

• AAC Bash script pass through slower than transcoding ?

  13 février 2015, par Threster

  I made a script for my Subsonic server which recognizes ALAC (lossless) from AAC (lossy) files. Because iTunes gives them both m4a extensions. ALAC gets transcoded, AAC is passed through. Only the pass through for AAC is 2-3x slower than the transcoding of ALAC ?

  I checked the aac files with the qt-faststart utility of ffmpeg for the moov atoms. qt-faststart gives output like this :

  ftyp          0 32
  
  moov         32 39003
  
  free      39035 38781
  
  mdat      77816 6479293
  
  last atom in file was not a moov atom

  So I think the moov atoms are in the beginning, which would be ok.

  Code of the actual bash script :

  #!/bin/sh
  
  # Author: poctum + Threster
  
  DEBUG=TRUE
  
  # Locations of various programs required
  
  FFMPEG=/usr/bin/ffmpeg
  
  CAT=/bin/cat
  
  FFPROBE=/usr/bin/ffprobe
  
  GREP=/bin/grep
  
  # Defaults and other variables 
  
  INFILE=$1
  
  MAXBITRATE=256
  
  
  
  # Send data to StdOut for echo's to show up in subsonic.log
  
  debugout() 
  
  {
  
      if [ $DEBUG = TRUE ]; then 
  
          echo "$@" 1>&2
  
      fi
  
  }
  
  
  
  # Capture the INFILE codec type, and then trim it.
  
  TUSSENCODEC=`$FFPROBE -v error -show_streams "$INFILE" | $GREP codec_name` 
  
  INCODEC=${TUSSENCODEC#*=}
  
  debugout  "tussencodec is $TUSSENCODEC and incodec is $INCODEC"
  
  
  
  if [ -z "${INCODEC}" ] ; then
  
      debugout "no codec detected in $INFILE inputfile"
  
  elif [ $INCODEC = aac ] ; then
  
      debugout "print $INCODEC is aac so  pass trough"
  
      $CAT "$INFILE" < /dev/null
  
  else
  
      debugout " print $INCODEC is  not aac so encoding to aac"
  
      $FFMPEG -i "$INFILE" -nostdin -c:a libfdk_aac -movflags +faststart -b:a "$MAXBITRATE"k -vn -f adts - < /dev/null
  
  fi

• get minimum value in bash script for video encoding

  26 novembre 2019, par Bardan Pokhrel

  I am a beginner in bash script (& coding) and I have gone through many sites for possible answer to my queries in order to find the minimum values in a calculated field. However, I haven’t found the solution yet.

  Here is the calculation I am trying....

  if (( $count == "3" )); then
  
      bitrate3=${inputbr}
  
      bitrate4=$((25 * ${bitrate3} / 100 )) 
  
      bitrate5=$((12 * ${bitrate3} / 100 ))
  
  else
  
      echo "nothing here"
  
  fi

  What I want is to set a minimum value out of two. For example I want to fix bitrate4 to either 652 or 25% of bitrate3. bitrate3 in this case is calculated using ffprobe. Please help.