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• using find in subprocess.call() gives error while the command executes properly from command prompt

  28 février 2018, par Devaraj GH

  C:\Windows\System32> ffmpeg -i D:\devaraj\KPIX_test.ts -vf "blackframe" -an -f n
  
  ull - 2>&1|find "Parsed" > D:\devaraj\info.txt

  this works fine , writes the file info.txt

  subprocess.call('ffmpeg' ,'-i', 'D:\devaraj\KPIX_test.ts' ,'-vf', '"blackframe"', 'D:\devaraj\KPIX_textfinal.mp3', '- 2>&1>','|','find', '"Parsed"', '>' ,'D:\devaraj\info.txt', 'shell=True')

  gives an error buffer size must be integer

  were as

  subprocess.call('ffmpeg -i D:\devaraj\KPIX_test.ts -vf "blackframe" -an -f n
  
  ull - 2>&1|find "Parsed" > D:\devaraj\info.txt', shell=True) 

  gives an error

  ’find’ is not recognized as an internal or external command,
  operable program or batch file.

  any help would be appreciated from d bottom of heart

• OpenCV Cmake unable to find ffmpeg lib

  22 février 2018, par URMISH THAKKER

  I am trying to compile OpenCV with ffmpeg support for ARM Platform on a x86 host.

  I downloaded and compiled ffmpeg for arm platform (both static - FFMPEG_ARM_LIB and dynamic libs - FFMPEG_ARM_LIB_SO)

  When I run cmake in opencv, it gives the following -

  --   Video I/O:
  
  --     DC1394 1.x:                  NO
  
  --     DC1394 2.x:                  NO
  
  --     FFMPEG:                      **NO**
  
  --       codec:                     NO
  
  --       format:                    NO
  
  --       util:                      NO
  
  --       swscale:                   NO
  
  --       gentoo-style:              YES
  
  --     GStreamer:                   NO
  
  --     OpenNI:                      NO
  
  --     OpenNI PrimeSensor Modules:  NO
  
  --     PvAPI:                       NO
  
  --     GigEVisionSDK:               NO
  
  --     UniCap:                      NO
  
  --     UniCap ucil:                 NO
  
  --     V4L/V4L2:                    NO/YES
  
  --     XIMEA:                       NO
  
  --     Xine:                        NO

  I changed the following flags to point to the lib paths of both ffmpeg static and dynamic libs-

  1. LD_LIBRARY_PATH
  2. C_INCLUDE_PATH
  3. CPLUS_INCLUDE_PATH
  4. PKG_CONFIG_PATH
  5. PKG_CONFIG_LIBDIR
  6. PATH
  7. CMAKE_LIBRARY_PATH
  8. CMAKE_INCLUDE_PATH

  However, the opencv is still not able to recognize the ffmpeg libs.

  My FFMPEG compilation command was

  ./configure --enable-shared --disable-static\
  
   --cross-prefix=arm-linux-gnueabi- --arch=armv7a\
  
   --target-os=linux --prefix=<path>
  
  </path>

  What am I doing wrong here ?
  1. Am I compiling the ffmpeg with the wrong option ?
  2. Am I missing some element in CMake which would make it point to the compiled ffmpeg lib for ARM on my system ?

• How to solve file path error while using ffprobe to find length of video file in python ?

  4 février 2018, par Mitchell Faas

  So, I’m trying to find the length of a video file by the methods discussed here : How to get the duration of a video in Python ?, Using ffmpeg to obtain video durations in python. But in doing so I run in to a problem which I haven’t been able to solve : I get

  FileNotFoundError:[WinError 2] The system cannot find the file specified

  after trying a bunch of troubleshooting steps I’ve started running in IPython and in cmd seperately to see where things might break down. Using a stripped down version of this code in IPython gives me

  In [11]: subprocess.Popen([ffmpeg_path+'ffprobe'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  Out[11]: 

  which seems to be fine, as is CMD at this point. So to adding slight complexity :

  In [17]: subprocess.Popen([ffmpeg_path+'ffprobe -i "F:/tst.mp4"'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  ---------------------------------------------------------------------------
  
  FileNotFoundError                         Traceback (most recent call last)
  
   in <module>()
  
  ----> 1 subprocess.Popen([ffmpeg_path+'ffprobe -i "F:/tst.mp4"'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  
  
  C:\Python\Anaconda3\lib\subprocess.py in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags, restore_signals, start_new_session, pass_fds, encoding, errors)
  
      705                                 c2pread, c2pwrite,
  
      706                                 errread, errwrite,
  
  --> 707                                 restore_signals, start_new_session)
  
      708         except:
  
      709             # Cleanup if the child failed starting.
  
  
  
  C:\Python\Anaconda3\lib\subprocess.py in _execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, unused_restore_signals, unused_start_new_session)
  
      988                                          env,
  
      989                                          cwd,
  
  --> 990                                          startupinfo)
  
      991             finally:
  
      992                 # Child is launched. Close the parent's copy of those pipe
  
  
  
  FileNotFoundError: [WinError 2] The system cannot find the file specified
  
  </module>

  This crashes IPython. Running the very same command ffprobe -i "F:/tst.mp4" in CMD works like a charm.

  Here’s what I tried : Changing / to \ and \ , adding and removing quotes around the file path, changing the path to C :\tst.mp4.

  Running the command os.system(ffmpeg_path+'ffprobe -i "F:/tst.mp4") does work.

  What could possibly be going wrong here ?