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• How to make linker ld find a file ?

  21 avril 2015, par haxan7

  I am cross compiling opencv with FFmpeg and it is throwing the following error :

  /root/work/codesourcery/arm-2013.05/bin/../lib/gcc/arm-none-linux-gnueabi/4.7.3/../../../../arm-none-linux-gnueabi/bin/ld : warning : libavcodec.so.56, needed by ../../lib/libopencv_highgui.so.2.4.10, not found (try using -rpath or -rpath-link)

  I have the libavcodec.so.56, and have put the relevant path to $PKG_CONFIG_PATH.

  doing a pkg-config —list-all | grep avcodec returns

  libavcodec                     libavcodec - FFmpeg codec library

  ls -al libs folder returns

  -rw-r--r-- 1 root root 93416352 Apr 21 06:57 libavcodec.a
  
  lrwxrwxrwx 1 root root       23 Apr 21 06:57 libavcodec.so -> libavcodec.so.56.34.100*
  
  lrwxrwxrwx 1 root root       23 Apr 21 06:57 libavcodec.so.56 -> libavcodec.so.56.34.100*
  
  -rwxr-xr-x 1 root root 10949836 Apr 21 06:57 libavcodec.so.56.34.100*

  Here are the contents of libavcodec.pc file

  prefix=/root/ARM_Install
  
  exec_prefix=${prefix}
  
  libdir=${prefix}/lib
  
  includedir=${prefix}/include
  
  
  
  Name: libavcodec
  
  Description: FFmpeg codec library
  
  Version: 56.34.100
  
  Requires: 
  
  Requires.private: libswresample >= 1.1.100, libavutil >= 54.22.101
  
  Conflicts:
  
  Libs: -L${libdir}  -lavcodec 
  
  Libs.private: -lxvidcore -lx264 -lm -pthread -ldl
  
  Cflags: -I${includedir}

  How can I make the liker find this file ?

• subprocess.call can't find file/shutil.which failed in pycharm

  4 décembre 2022, par Percy Yang

  I am trying to transform a mp3 to a wav file in pycharm using subprocess

  


  import subprocess
subprocess.call(['ffmpeg', '-i','test.mp3','test.wav'])


  


  It returns error of not finding file, so I change the 'ffmpeg' to its path on my pc and it work.

  


  The problem is that I am making an app and others might install ffpmeg on other's location (since it is download with zip and can be unzip at any place), but I don't know how to get its full path.

  


  I tried using os module

  


  import os
print(os.path('ffmpeg.exe'))


  


  but it seems like it is not able to get the path of exe

  


  Traceback (most recent call last):&#xA;  File "C:\Users\Percy\PycharmProjects\APP\test3.py", line 8, in <module>&#xA;    print(os.path(&#x27;ffmpeg.exe&#x27;))&#xA;TypeError: &#x27;module&#x27; object is not callable&#xA;</module>

  


  I also tried shutil module

  


  import shutil
print(shutil.which('ffmpeg'))
print(shutil.which('ffmpeg.exe'))


  


  but it returns 2 None (prob wrong cause I am 100% sure I have installed ffmpeg)

  


  None
None


  


  I want to ask if there is any way to get the full path of ffmpeg in pycharm or any method that I can make ffmpeg install in designated path with the app when it is downloaded by users

  


• How to extract frame types along with motion vectors using extract_mvs.c from ffmpeg

  26 février 2018, par helmo

  I have been researching ways to get frame types (I, P, B) along with the motion vector data returned from extract_mvs.c in the examples folder in ffmpeg.

  The extract_mvs.c file after it is compiled, returns information like this :

  framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags
  
  2,-1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,  24,   8,  24,   8,0x0
  
  2, 1,16,16,  40,   8,  40,   8,0x0
  
  2, 1,16,16,  56,   8,  56,   8,0x0
  
  2, 1,16,16,  72,   8,  72,   8,0x0
  
  2, 1,16,16,  88,   8,  88,   8,0x0
  
  ...
  
  297, 1,16,16, 248, 280, 248, 280,0x0
  
  297, 1,16,16, 264, 280, 264, 280,0x0
  
  297,-1,16,16, 278, 279, 280, 280,0x0
  
  297, 1,16,16, 280, 280, 280, 280,0x0
  
  297, 1,16,16, 296, 280, 296, 280,0x0
  
  297, 1,16,16, 312, 280, 312, 280,0x0
  
  297, 1,16,16, 328, 280, 328, 280,0x0
  
  297, 1,16,16, 344, 280, 344, 280,0x0

  Along with this information, I would like to output frame type so that I know framenum = 2 is, for example, a ’B’ frame.

  I tried different things, one of which was using a separate command :

  ffprobe input.mp4 -show_frames | grep -E 'pict_type|coded_picture_number'

  But the problem with this command is that it returns data like :

  pict_type=I
  
  coded_picture_number=0
  
  pict_type=B
  
  coded_picture_number=2
  
  pict_type=P
  
  coded_picture_number=1
  
  pict_type=B
  
  coded_picture_number=4
  
  pict_type=P
  
  coded_picture_number=3
  
  ....
  
  pict_type=P
  
  coded_picture_number=293
  
  pict_type=B
  
  coded_picture_number=297
  
  pict_type=B
  
  coded_picture_number=296

  And there is no much I can relate here between coded_picture_number and framenum. The former starts counting from 0 and the later from 2. I assume framenum starting from 2, means the count from this variable is actually from 1, and it ignored 1 in the extraction process as it is maybe an I frame thus no motion vectors.

  So, how can we use only extract_mvs.c to get not only that information it provides but also the frame types in the returned table. Any hints either syntax/command-wise or in editing the c file would be appreciated. Thanks in advance.