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• Opencv VideoCapture always returns false on Heroku

  27 juin 2022, par Dacian Mujdar

  I'm using the following code to open a video stream :

  


  import cv2
video = cv2.VideoCapture()
video.open("some_m3u8_link")
success, image = video.read()


  


  However, even if the code works as intended locally, on Heroku success is always false.

  


  I'm using cedar-14 stack with the following buildpacks :

  


  


  heroku/python

  


  https://github.com/jonathanong/heroku-buildpack-ffmpeg-latest.git

  


  


  (I tried several buildpack options for ffmpeg)

  


  Running ffmpeg --version on heroku instance will return ffmpeg version 4.0-static https://johnvansickle.com/ffmpeg/

  


  Is there any setting/configuration I missed in order to make it work on deployment ? Thank you !

  


  Later edit : I tried several links for "some_m3u8_link" including from twitch and other streaming services (including traffic streaming li
An example for reproducing :

  


  python -c "import cv2; video=cv2.VideoCapture(); video.open('https://hddn01.skylinewebcams.com/live.m3u8?a=5tm6kfqrhqbpblan9j5d4bmua4'); success, image = video.read(); print(success)"


  


  Returns True on local machine and False on Heroku.

  


  (the link is taken from here)

  


• qt-faststart - stco offset bug fix

  1er juin 2018, par erankor

  qt-faststart - stco offset bug fix
  when the last offsets in the stco atom are close to 4GB, the addition of
  
  the moov atom size can overflow, causing corruption near the end of the
  
  mp4 file.
  
  this patch upgrades all stco atoms to co64 when such an edge case is
  
  detected. in order to accomplish this, the implementation was changed to
  
  walk the atom tree, instead of searching for the strings 'stco'/'co64'.
  
  this was required since when an stco atom is changed to co64, its size
  
  changes, and the sizes of all containing atoms (moov, trak, etc.) have
  
  to be updated as well.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] tools/qt-faststart.c

• Error issuing complex shell command in python via subprocess

  4 juillet 2018, par user16171

  I’ve converted about 100 video tapes and now have 100 folders full of .dv files (each folder’s name is a date). In each folder, I want to combine all of the .dv files into one x265 mp4. I have figured out the ffmpeg command to do this, and I’ve written a simple Python script to traverse the folder hierarchy and print out the ffmpeg command to do each folder’s conversion. I’d like to set it up to just run each folder in series - it will take about a week to do the entire conversion, leaving me with about 5GB of video to use/post, etc. vs the 1.5TB of raw .dv files.

  The shell command looks like this :

  ffmpeg -f concat -i <(for f in FULL_PATH_TO_FILES/*.dv; do echo "file '$f'"; done) \
  
    -c:v libx265 -crf 28 -c:a aac -b:a 128k \ 
  
    -strict -2 FULL_PATH_TO_FILES/FOLDERNAME.mp4

  I can run that as a shell command, and it works fine. I could use the python script to generate the 100 commands and just copy and paste them into my shell one at a time. But I’d rather just have them run in series.

  I’ve tried various incarnations of os.system and subprocess.call or subprocess.Popen, and they all error.

  I build up the command and issue subprocess.call(command), which gives this error :

  "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 522, in call
  return Popen(*popenargs, **kwargs).wait()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in init
  errread, errwrite)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
  raise child_exception
  OSError : [Errno 2] No such file or directory

  I’ve also tried building up the command, as described in many of the other threads I’ve read, but it does not work, and I assume it’s because of the for-loop I have in the shell command.

  So, what’s the best way to do this ? Obviously, a shell-jockey could just tell me how to do this via the shell, but I’m more comfortable using Python to traverse the directories and build up the ffmpeg command.

  For what it’s worth, here is the whole script :

  import os
  
  import subprocess
  
  t1 = "ffmpeg -f concat -i <(for f in "
  
  t2 = "/*.dv; do echo \"file '$f'\"; done) -c:v libx265 -crf 28 -c:a aac -b:a 128k -strict -2 "
  
  t3 = ".mp4"
  
  rootDir = ROOTDIR
  
  for dirName, subdirList, fileList in os.walk(rootDir):
  
      S = dirName.split('/')    
  
      if S[-1] == "Media":
  
          moviename = S[-2].split(".")[0] # e.g. "19991128_Thanksgiving"
  
          command = t1 + dirName + t2 + dirName + "/" + moviename + t3
  
          if sum([".mp4" in fname for fname in fileList]) == 0: # don't bother if there is already a mp4 file in the folder
  
              cmd_list = [t1,dirName,t2,dirName,"/",moviename,t3]
  
              print command
  
              print
  
              print
  
              subprocess.call(command)