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• Unable to link against FFmpeg libaries

  2 mars 2023, par Cody

  I tried to build this, but always got link-time error.

  



  #include <libavutil></libavutil>log.h>    &#xA;int main(int argc, char *argv[])&#xA;{&#xA;    ::av_log_set_flags(AV_LOG_SKIP_REPEATED);&#xA;    return 0;&#xA;}&#xA;

  



  My distro is Debian GNU/Linux 8 (jessie). The FFmpeg was built by myself, and the configure command was...

  



  $ ./configure --prefix=/usr/local --disable-static --enable-shared \
> --extra-ldflags='-Wl,-rpath=/usr/local/lib'


  



  The link-error is as follows.

  



  $ g++ foo.cpp -D__STDC_CONSTANT_MACROS -Wall \
> -Wl,-rpath=/usr/local/lib \
> $(pkg-config --cflags --libs libavutil)
/tmp/ccKzgEFb.o: In function `main':
foo.cpp:(.text+0x17): undefined reference to `av_log_set_flags(int)'
collect2: error: ld returned 1 exit status


  



  where the output of pkg-config is...

  



  $ pkg-config --cflags --libs libavutil
-I/usr/local/include -L/usr/local/lib -lavutil


  



  The objdump shows that the shared object libavutil.so does have av_log_set_flogs inside.

  



  $ objdump --dynamic-syms /usr/local/lib/libavutil.so | grep 'av_log_set_flags'
000260f0 g    DF .text  0000000a  LIBAVUTIL_54 av_log_set_flags


  



  Please note that the g++ command used to build the above application had a linker option -Wl,-rpath=/usr/local/lib, though it still doesn't work. Also, I've tried to monitor with inotifywait if the other version provided by the distro were called. They were not, and the one being opened during execution of g++ was /usr/local/lib/libavutil.so.

  



  Summary :

  



  


  1. /usr/local/lib/libavutil.so does have the symbol.

  


  2. -rpath was used to force to link against the shared library.

  


  3. Why link-time error ? T_T

  


  



  Any suggestion or information would be highly appreciated ! Thanks !

  



  REEDIT : ffplay works fine and ldd shows it use /usr/local/lib/libavutil.so. So, the libraries seems not broken, and the problem becomes how to build my own codes to use the libraries.

  


• How can I stream then play YUV format with/without VLC/FFMPEG ?

  13 janvier 2023, par orfruit

  I'm able to play a local YUV file through VLC (as expected)

  


  .\vlc.exe --demux rawvideo --rawvid-fps 25 --rawvid-width 480 --rawvid-height 360 --rawvid-chroma I420 out.yuv


  


  Also FFPLAY is playing well

  


  .\ffplay.exe -f rawvideo -pixel_format yuv420p -video_size 480x360 out.yuv


  


  Conversion to YUV was done with FFMPEG

  


  .\ffmpeg.exe -i "video.mp4" -c:v rawvideo -pixel_format yuv420p out.yuv


  


  However, I'm not able o stream it and play'it over local network.
I know, it sounds crazy :) but I plan to use VLC as a monitor/debugger for some YUV data.

  


  The original MP4 file is streamed/played fine with VLC (test on the same computer)

  


  .\vlc.exe "video.mp4" --sout="#std{access=http, mux=ts, dst=:55555/}"
.\vlc.exe http://192.168.0.174:55555/


  


  So the big question !
How can I stream the YUV format and VLC recognise an play it as well ?

  


  All that I tried with VLC is not playable.

  


  Thanks for any hints !

  


• ffmpeg - Unable to record screen and speaker audio at the same time

  11 janvier 2023, par dems98

  I'm trying to record my screen and speaker audio with ffmpeg but I'm facing various problems.

  


  This is the command I'm using :

  


  ffmpeg -video_size 1920x1080 -framerate 60 -f x11grab -i :0.0 -f pulse -ac 2 -i alsa_output.pci-0000_2d_00.4.analog-stereo.monitor output.mp4


  


  but the output video is really slow and out of sync with the audio.
  
Moreover, I'm getting these warnings :

  


  [x11grab @ 0x563635302480] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
[aac @ 0x563635319f40] Queue input is backward in time04.49 bitrate= 466.9kbits/s dup=268 drop=45 speed=1.84x    
[mp4 @ 0x5636353172c0] Non-monotonous DTS in output stream 0:1; previous: 217669, current: 210387; changing to 217670. This may result in incorrect timestamps in the output file.                                                                                        


  


  When recording the screen with alsa source (microphone), the output video has no problems.

  


  How can I solve ?