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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 ?

• Encode live audio stream with ffmpeg

  11 novembre 2015, par Victor Canezin de Oliveira

  Someone please help me.

  I’m trying to encode a live audio stream with ffmpeg. I’m using it Chrome’s native client.

  It’s getting the audio from GetUserMedia() and sending it to pnacl. It receives the audio and send it to ffmpeg to encode. The problem is the final audio is chopped.

  I think the problem is that the codec frame_size is larger than the stream nb_samples (1152 and 480 respectively) and it’s leaving a "blank" audio data at the end of each frame (I’m no audio expert).

  I am creating the AVFrame like this :

  AVFrame *frame = av_frame_alloc();
  
  frame->nb_samples = nb_samples; //(I get it from the stream)
  
  AVSampleFormat sample_fmt = ost->st->codec->sample_fmt;
  
  // nb_channels, buffer and buffer_size I get from the stream
  
  
  
  avcodec_fill_audio_frame(frame, nb_channels, sample_fmt, buffer, buffer_size, 0);

  And encoding with avcodec_encode_audio2

  I am using a mix of nacl example and muxing.c example from ffmpeg.

  Can someone help me ?

• FFmpeg —> Create ouput file takes 20 seconds

  5 novembre 2015, par Sven

  When i try to convert a http stream (http://192.168.1.100:8866/live?channeloid=7163&client=MB3.1) from nextpvr (tv tuner software) with ffmpeg it takes 20 seconds before he creates "df313844aed43acb6b26ee95d3023f88.m3u8" file.

  I am not a ffmpeg expert, can somebody with more experience help me ?
  Below you can find the parameters i pass-trough to ffmpeg. And you can also see what the output is.

  When i try to open te stream with "VLC Player" it opens directly, so it’s definitely to do with the parameters i provide. But i really don’t know what’s wrong.

  http://pastebin.com/nW3XpQK6