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• x86inc : Clear __SECT__

  26 mai 2015, par Timothy Gu

  x86inc : Clear __SECT__
  This commit silences warning(s) like :
      libavcodec/x86/fft.asm:93 : warning : section flags ignored on section
  
      redeclaration
  The cause of this warning is that because `struc` and `endstruc` attempts to
  
  revert to the previous section state [1]. The section state is stored in the
  
  macro __SECT__, defined by x86inc.asm to be `.note.GNU-stack ...`, through the
  
  `SECTION` directive [2].  Thus, the `.note.GNU-stack` section is defined twice
  
  (once in x86inc.asm, once during `endstruc`), causing the warning.
  That is the first part of the commit : using the primitive `[section]` format
  
  for .note.GNU-stack etc., which does not update `__SECT__` [2].
  That fixes only half of the problem. Even without any `SECTION` directives,
  
  `__SECT__` is predefined as `.text`, which conflicting with the later
  
  `SECTION_TEXT` (which expands to `.text align=16`).
  [1] : http://www.nasm.us/doc/nasmdoc6.html#section-6.4
  
  [2] : http://www.nasm.us/doc/nasmdoc6.html#section-6.3
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavutil/x86/x86inc.asm

• Problem while building libffmpeg.so from ffmpeg sources (undefined symbol : avcodec_version)

  10 octobre 2023, par serggt1

  I'm trying to build libffmpeg.so shared library from sources on Linux. Sources are here FFmpeg.git.

  


  I run

  


  ./configure
make -j4

gcc -shared \
    libavcodec/libavcodec.a \
    libavdevice/libavdevice.a \
    libavfilter/libavfilter.a \
    libavformat/libavformat.a \
    libavutil/libavutil.a \
    libswresample/libswresample.a \
    libswscale/libswscale.a \
    -o libffmpeg.so


  


  The problem is the resulting libffmpeg.so is only 15 KB and says

  


  dlsym fail : /opt/yandex/browser/libffmpeg.so: undefined symbol: avcodec_version


  


  What do I wrong and how to link the library in correct way ?

  


  UPD :

  


  Now trying with this :

  


  ./configure --enable-pic --disable-programs  --enable-gpl --enable-version3 --enable-nonfree

make -j4

ld \
    -rpath-link=/usr/lib \
    -L/usr/lib \
    -L/lib \
    --library=c --library=m --library=z --library=dl --library=log \
    -soname libffmpeg.so -shared -nostdlib -Bsymbolic --whole-archive --no-undefined \
    libavcodec/libavcodec.a \
    libavdevice/libavdevice.a \
    libavfilter/libavfilter.a \
    libavformat/libavformat.a \
    libavutil/libavutil.a \
    libswresample/libswresample.a \
    libswscale/libswscale.a \
    -o libffmpeg.so


  


  Error is ld: cannot find -lc: No such file or directory

  


• Debugging Gstreamer pipeline with tee and a filesink in C

  28 septembre 2020, par NicolasBourbaki

  There is an excellent example on how to construct a C program using GStreamer and its tee and filesink elements on https://gist.github.com/crearo/a49a8805857f1237c401be14ba6d3b03.
(Another one can be found on https://gstreamer.freedesktop.org/documentation/tutorials/basic/multithreading-and-pad-availability.html?gi-language=c).

  


  The idea of the tee element in a pipeline is similar like the tee program in Unix : Like a T-shaped tube, it allows to add a bifurcation to a pipeline, which is in my case used to display a video stream to the screen (which works perfectly) and writing it at the same time to a file (which doesn't work - the file is created but stays empty, i.e. has a size of 0 bytes after closing the program).

  


  I deviated from the examples mentioned above by neither having a queue element for recording (because I also don't have one for displaying, which works) as well as neither having an encoder nor a muxer. Although this might be a problem for what gets written to the file in the end, I would expect that there is written something to the file at all.

  


  The program does compile. What additional diagnostics could I run in order to pin down the problem ?