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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 ?

• 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 ?

• 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 ?