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• Why use sysconf(_SC_NPROCESSORS_CONF) to get the number of CPU cores in x264 ?

  5 novembre 2017, par bknieven

  I find x264 use sysconf(_SC_NPROCESSORS_CONF) instead of sysconf(SC_NPROCESSORS_ONLN) to get the number of CPU cores.

  Here is the code snippet in x264/common/cpu.c :

  ...
  
  #ifdef __ANDROID__
  
      // Android NDK does not expose sched_getaffinity
  
      return sysconf( _SC_NPROCESSORS_CONF );
  
  #else
  
      ...
  
  ....

  And I find the difference between _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN in this manual :

  sysconf (_SC_NPROCESSORS_CONF) which returns the number of processors
  the operating system configured. But it might be possible for the
  operating system to disable individual processors and so the call
  sysconf (_SC_NPROCESSORS_ONLN) returns the number of processors which
  are currently online (i.e., available).

  I have two questions :

  1. What is the difference between "the number of processors the operating system configured" and "the number of processors which are currently online" ?
  2. Why x264 use _SC_NPROCESSORS_CONF in Android to get the number of CPU cores ?

• FFMPEG : invalid data found when processing input, but same input works in FFPLAY

  20 janvier 2023, par SoerenS

  I have a TCP stream with raw 8-bit image data (1280x720) that I receive and display with FFPLAY without problems, but it´s not possible to process the same input with FFMPEG.

  


  This works :

  


  ffplay -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720

  


  But when I try to process the same stream with FFMPEG, it always immediatly returns after the first frame with :

  


  tcp://127.0.0.1:8485\?listen: Invalid data found when processing input

  


  I tried the following commands :

  


  ffmpeg -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720
ffmpeg -i tcp://127.0.0.1:8485\?listen -f rawvideo -pixel_format gray -video_size 1280x720 -c:v mjpeg -f mjpeg -qscale 6 test.avi

  


  Same behavior under Windows and Ubuntu. FFMPEG and FFPLAY are from the same set of prebuilt binaries. Version command returns N-107067-g5d5a014199-20220609. Unfortunately I have no access to the code of the stream origin. Any idea about a potential root-cause and what I could try ?

  


• 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