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• FFmpeg : Reading the source code, how do I understand the impact of a given configuring option ?

  25 février 2016, par Antonio

  I was trying to investigate the impact of the --enable-gray configuring option on the ffmpeg code. However, if I download the source and grep the entire project for enable-gray, the only entry I find is in the configure file, in the help section. Is this option used at all ? If it is used, how do I find the section of code which are activated by using this option ?

  Even using a regex search with enable.*gray doesn’t bring any additional results.

• Upload video, split it by size (on mb) and play it

  4 février 2016, par Marco Ganzo

  I’m trying to learn some using of code, and i’m want to know if it possible upload video, after upload split it by Mb.

  For example :
  i have video . mp4 2.3 Mb that i uploaded. i want it split to :

  video 1 . mp4 (1 MB)
  
  video 2 . mp4 (1 MB)
  
  video 3 . mp4 (0.3 MB)

  And after it i want open for example URL :

  example.com/video/video.mp4

  and it will know that the video is from 4 sources.

  Is it possible ?

• Linking problems using CMake

  5 décembre 2013, par Zoellick

  I'm writing an application containig 2 internal libraries and depends on more 2 external libraries (ffmpeg and opencv). I'm also using CMake to produce UNIX makefiles. And the problem is when i'm trying to build sources, it compiles but don't link with ffmpeg at all and the next output the linker gives :

  ../../Decoder/libDecoder.a(ConverterAVFrameToRGB.cpp.o): In function `FaceVideo::ConverterAVFrameToRGB::to_rgb_conversion(std::vector >&, int, int, int)':
  
  ConverterAVFrameToRGB.cpp:(.text+0x990): undefined reference to `av_frame_free'
  
  ../../Decoder/libDecoder.a(FfmpegDecoder.cpp.o): In function `FaceVideo::FfmpegDecoder::destroy()':
  
  FfmpegDecoder.cpp:(.text+0xa30): undefined reference to `av_frame_free'
  
  ../../Decoder/libDecoder.a(FfmpegDecoder.cpp.o): In function `FaceVideo::FfmpegDecoder::decode_next_chunk(int)':
  
  FfmpegDecoder.cpp:(.text+0xb6b): undefined reference to `av_frame_clone'
  
  FfmpegDecoder.cpp:(.text+0xc13): undefined reference to `av_frame_free'
  
  ../../Decoder/libDecoder.a(FfmpegEncoder.cpp.o): In function `FaceVideo::FfmpegEncoder::destroy()':
  
  FfmpegEncoder.cpp:(.text+0x132): undefined reference to `avcodec_free_frame'
  
  ../../Decoder/libDecoder.a(FfmpegEncoder.cpp.o): In function `FaceVideo::FfmpegEncoder::encode()':
  
  FfmpegEncoder.cpp:(.text+0x4c4): undefined reference to `avcodec_encode_video2'
  
  FfmpegEncoder.cpp:(.text+0x592): undefined reference to `avcodec_encode_video2'
  
  ../../Decoder/libDecoder.a(FrameSaver.cpp.o): In function `FaceVideo::FrameSaver::saver(std::vector >&, int, int, int)':
  
  FrameSaver.cpp:(.text+0x869): undefined reference to `av_frame_free'
  
  collect2: ld returned 1 exit status

  That's excatly what i don't want to see.

  There are three Cmake files : two for internal libraries (use

  add_library(Decoder ${SOURCES_DECODER})
  
               and 
  
  add_library(Detector ${SOURCES_DETECTOR})

  in them) and one for main executable (use

  add_executable(Tool ${SOURCES_TOOL})
  
               and
  
  target_link_libraries (Tool Decoder avutil avcodec swscale avformat Detector ${OpenCV_LIBS})

  in it).

  As far as i understand from CMake manuals and examples, this should make linker link this libraries together, but no effect.

  I've been trying lot of things such as :
  1) Adding link_directories() with path to libraries (/usr/lib/x86_64-linux-gnu/ for me) wherever it's possile, nothing changed.
  2) Linking every library separately, i mean i tried do something like this in my internal libraries CMake files : target_link_libraries (Decoder avutil avcodec swscale avformat). And then link library together into my Tool CMake file : target_link_libraries (Tool Decoder Detector).
  3) Editing output makefiles.
  4) Compiling simple one-file application just to test whether i can do it or not. I can. g++ -lavcodec -o out mysource.cpp works perfectly.
  5) Compling ffmpeg manually and installing it.

  The fact is i realy don't know what should i do. I have no idea. And i would very appreciate your every answer.

  Output when CMAKE_VERBOSE_MAKEFILE is set

   !
  /usr/bin/c++ -march=x86-64 -Wall -fPIC -pthread -std=c++0x -D__STDC_CONSTANT_MACROS -march=x86-64 -fPIC CMakeFiles/FaceDetectorTool.dir/home/anton/Programming/facevideo/branches/Stream_Prototype/src/tools/FaceDetectorTool/facedetector.cpp.o -o FaceDetectorTool -rdynamic ../../Detector/libDetector.a ../../Decoder/libDecoder.a -lavutil -lavcodec -lswscale -lavformat /usr/local/lib/libopencv_videostab.so.2.4.7 /usr/local/lib/libopencv_video.so.2.4.7 /usr/local/lib/libopencv_ts.a /usr/local/lib/libopencv_superres.so.2.4.7 /usr/local/lib/libopencv_stitching.so.2.4.7 /usr/local/lib/libopencv_photo.so.2.4.7 /usr/local/lib/libopencv_ocl.so.2.4.7 /usr/local/lib/libopencv_objdetect.so.2.4.7 /usr/local/lib/libopencv_nonfree.so.2.4.7 /usr/local/lib/libopencv_ml.so.2.4.7 /usr/local/lib/libopencv_legacy.so.2.4.7 /usr/local/lib/libopencv_imgproc.so.2.4.7 /usr/local/lib/libopencv_highgui.so.2.4.7 /usr/local/lib/libopencv_gpu.so.2.4.7 /usr/local/lib/libopencv_flann.so.2.4.7 /usr/local/lib/libopencv_features2d.so.2.4.7 /usr/local/lib/libopencv_core.so.2.4.7 /usr/local/lib/libopencv_contrib.so.2.4.7 /usr/local/lib/libopencv_calib3d.so.2.4.7 -ldl -lm -lpthread -lrt /usr/local/lib/libopencv_nonfree.so.2.4.7 /usr/local/lib/libopencv_ocl.so.2.4.7 /usr/local/lib/libopencv_gpu.so.2.4.7 /usr/local/lib/libopencv_photo.so.2.4.7 /usr/local/lib/libopencv_objdetect.so.2.4.7 /usr/local/lib/libopencv_legacy.so.2.4.7 /usr/local/lib/libopencv_video.so.2.4.7 /usr/local/lib/libopencv_ml.so.2.4.7 /usr/local/lib/libopencv_calib3d.so.2.4.7 /usr/local/lib/libopencv_features2d.so.2.4.7 /usr/local/lib/libopencv_highgui.so.2.4.7 /usr/local/lib/libopencv_imgproc.so.2.4.7 /usr/local/lib/libopencv_flann.so.2.4.7 /usr/local/lib/libopencv_core.so.2.4.7 -Wl,-rpath,/usr/local/lib