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• Concat video files on linux by creating chapters

  3 mars 2019, par KK-Media

  I do have a bigger range of video files I would like to concat and mux into MKV via CLI. Additionally I do need to keep the structure of the files by generating chapters in the output file which represent the single files.

  I usually mux video files with mkvtoolnix but I did not find a way to concat various files by generating chapters.

  Does anybody knows a quick Linux CLI way to do this ?
  Thanks

• checkasm : use perf API on Linux ARM*

  1er septembre 2017, par Clément Bœsch

  checkasm : use perf API on Linux ARM*
  On ARM platforms, accessing the PMU registers requires special user
  
  access permissions. Since there is no other way to get accurate timers,
  
  the current implementation of timers in FFmpeg rely on these registers.
  
  Unfortunately, enabling user access to these registers on Linux is not
  
  trivial, and generally involve compiling a random and unreliable github
  
  kernel module, or patching somehow your kernel.
  Such module is very unlikely to reach the upstream anytime soon. Quoting
  
  Robin Murphin from ARM :
  > Say you do give userspace direct access to the PMU ; now run two or more
  
  > programs at once that believe they can use the counters for their own
  
  > "minimal-overhead" profiling. Have fun interpreting those results...
  
  >
  
  > And that's not even getting into the implications of scheduling across
  
  > different CPUs, CPUidle, etc. where the PMU state is completely beyond
  
  > userspace's control. In general, the plan to provide userspace with
  
  > something which might happen to just about work in a few corner cases,
  
  > but is meaningless, misleading or downright broken in all others, is to
  
  > never do so.
  As a result, the alternative is to use the Performance Monitoring Linux
  
  API which makes use of these registers internally (assuming the PMU of
  
  your ARM board is supported in the kernel, which is definitely not a
  
  given...).
  While the Linux API is obviously cross platform, it does have a
  
  significant overhead which needs to be taken into account. As a result,
  
  that mode is only weakly enabled on ARM platforms exclusively.
  Note on the non flexibility of the implementation : the timers (native
  
  FFmpeg vs Linux API) are selected at compilation time to prevent the
  
  need of function calls, which would result in a negative impact on the
  
  cycle counters.
  

  • [DH] configure
  • [DH] tests/checkasm/checkasm.c
  • [DH] tests/checkasm/checkasm.h

• Compiling ffmpeg for Android using Linux

  1er juillet 2015, par VEP10

  I’d like to test the ijkplayer for android project according to this :
  https://github.com/bbcallen/ijkplayer/blob/master/README.md
  When I am compiling the ffmpeg (./compile-ffmpeg.sh) at the "configurate ffmpeg" phase I get the following message : arm-linux-androideabi-gcc is unable to create an executable file. C compiler test failed.
  This part of the compile-ffmpeg.sh file :

  echo "\n--------------------"
  
  echo "[*] configurate ffmpeg"
  
  echo "--------------------"
  
  cd $FF_SOURCE
  
  if [ -f "./config.h" ]; then
  
      echo 'reuse configure'
  
  else
  
      ./configure $FF_CFG_FLAGS \
  
          --extra-cflags="$FF_CFLAGS $FF_EXTRA_CFLAGS" \
  
          --extra-ldflags="$FF_DEP_LIBS $FF_EXTRA_LDFLAGS"
  
      make clean
  
  fi 

  At the end of the config.log file I found the problem :

  zoompan_filter_deps='swscale'
  
  WARNING: arm-linux-androideabi-pkg-config not found, library detection may fail.
  
  mktemp -u XXXXXX
  
  tHt73A
  
  check_ld cc
  
  check_cc
  
  BEGIN /tmp/ffconf.mvjZdW0f.c
  
      1   int main(void){ return 0; }
  
  END /tmp/ffconf.mvjZdW0f.c
  
  arm-linux-androideabi-gcc -O3 -Wall -pipe -std=c99 -ffast-math -fstrict aliasing -Werror=strict-aliasing -Wno-psabi -Wa,--noexecstack -DANDROID -DNDEBUG -march=armv7-a -mcpu=cortex-a8 -mfpu=vfpv3-d16 -mfloat-abi=softfp -mthumb -mcpu=cortex-a8 -c -o /tmp/ffconf.ZKAEl7Bh.o /tmp/ffconf.mvjZdW0f.c
  
  as: unrecognized option '-mcpu=cortex-a8'
  
  C compiler test failed.

  I am sure that the assembler knows the cortex-a8 cpu option. The problem is anywhere else.

  Environment :

  Ubuntu 14.04

  NDK : r10e

  arm-linux-androideabi-4.8

  gcc-4.6

  Please help !