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• opencv V3 mixing shared and non shared

  31 décembre 2015, par Kellerspeicher

  The current stable (V3.0.0) and unstable (V3.1.0) version of openCV is mixing shared and non shared libraries if compiled on an Ubuntu 14.04.3 LTS.

  Linking CXX shared library ../../lib/libopencv_videoio.so
  
  /usr/bin/ld: /usr/local/lib/libavcodec.a(avpacket.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a shared object; recompile with -fPIC
  
  /usr/local/lib/libavcodec.a: error adding symbols: Bad value
  
  collect2: error: ld returned 1 exit status
  
  make[2]: *** [lib/libopencv_videoio.so.3.1.0] Error 1
  
  make[1]: *** [modules/videoio/CMakeFiles/opencv_videoio.dir/all] Error 2
  
  make: *** [all] Error 2

  Trying to create libopencv_videoio.so using libavcodec.a seems to be the problem. There is a bug report about that, but it is only giving the advice to check if libavcodec.so is installed (which is) and a workaround to use -DBUILD_SHARED_LIBS=OFF to prevent creation of shared libraries. Does anyone knows the reason for this problem. The openCV people just state the Ubuntu packaged ffmpeg library to be not correct. Any idea ?

  The problem seems to be old. I just found a very similar question not answered but commented with the advice of compiling ffmpeg with ./configure --enable-shared. But there is already a shared library /usr/lib/x86_64-linux-gnu/libavcodec.so which obviously is not found. I am not a cmake expert but couldn’t it be a problem of a miss leaded build process ?

• Can't maintain desired fps with ffmpeg live stream when overlay is added

  1er avril 2019, par jawsware

  I’m attempting to produce a 4K live stream for YouTube.

  I’m capturing 2160p30 frames from a BlackMagic Design DeckLink Mini Recorder. I’m passing those frames to ffmpeg in their raw 8-bit 4:2:2 format. I’m able to achieve 30 fps encoding ( 16kbits/s and q= in the high 20s to low 30s) with my current parameters which are :

  ffmpeg -threads:v 2 -threads:a 8 -filter_threads 2
  
  -f rawvideo -framerate 30 -pixel_format uyvy422 -video_size 3840x2160 -i \\.\pipe\videopipe
  
  -f s16le -ac 2 -ar 44100 -i \\.\pipe\audiopipe
  
  -r 30 -g 60 -c:v h264_nvenc -pix_fmt yuv420p -preset fast -profile main
  
  -b:v 16000K -maxrate 24000k -bufsize 6000k
  
  -f flv "rtmp://a.rtmp.youtube.com/live2/xxxx-xxxx-xxxx-xxxx"

  I’m dilemma is that once I introduce an overlay graphic, my encoding fps drops to 28 at best. Which leads me to believe I’m barley achieving the 30 fps without the overlay. I’m only adding these parameters to include the overlay :

  -i logo.png
  
  
  
  -filter_complex "overlay=100:100"

  I further diminish the encoding fps (20 fps max) when I introduce a dynamic overlay which I feed to ffmpeg through an additional pipe.

  My questions are 1.) is there a better set a parameters I could be using to encode the 4K stream ? 2.) is there a better way to include the overlay ?

• avdevice/decklink_enc : Add support for compressed AC-3 output over SDI

  7 avril 2023, par Devin Heitmueller

  avdevice/decklink_enc : Add support for compressed AC-3 output over SDI
  Extend the decklink output to include support for compressed AC-3,
  
  encapsulated using the SMPTE ST 377:2015 standard.
  This functionality can be exercised by using the "copy" codec when
  
  the input audio stream is AC-3.  For example :
  ./ffmpeg -i /foo.ts -codec:a copy -f decklink 'UltraStudio Mini Monitor'
  Note that the default behavior continues to be to do PCM output,
  
  which means without specifying the copy codec a stream containing
  
  AC-3 will be decoded and downmixed to stereo audio before output.
  Thanks to Marton Balint for providing feedback.
  Signed-off-by : Devin Heitmueller <dheitmueller@ltnglobal.com>
  
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavdevice/decklink_enc.cpp