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• Programming Language Levels

  20 mai 2011, par Multimedia Mike — Programming

  I’ve been doing this programming thing for some 20 years now. Things sure do change. One change I ponder from time to time is the matter of programming language levels. Allow me to explain.

  The 1990s
  When I first took computer classes in the early 1990s, my texts would classify computer languages into 3 categories, or levels. The lower the level, the closer to the hardware ; the higher the level, the more abstract (and presumably, easier to use). I recall that the levels went something like this :

  • High level : Pascal, BASIC, Logo, Fortran
  • Medium level : C, Forth
  • Low level : Assembly language

  Keep in mind that these were the same texts which took the time to explain the history of computers from mainframes -> minicomputers -> a relatively recent phenomenon called microcomputers or "PCs".

  Somewhere in the mid-late 1990s, when I was at university, I was introduced to a new tier :

  • Very high level : Perl, shell scripting

  I think there was some debate among my peers about whether C++ and Java were properly classified as high or very high level. The distinction between high and very high, in my observation, seemed to be that very high level languages had more complex data structures (at the very least, a hash / dictionary / associative array / key-value map) built into the language, as well as implicit memory management.

  Modern Day
  These days, the old hierarchy is apparently forgotten (much like minicomputers). I observe that there is generally a much simpler 2-tier classification :

  • Low level : C, assembly language
  • High level : absolutely every other programming language in wide use today

  I find myself wondering where C++ and Objective-C fit in this classification scheme. Then I remember that it doesn’t matter and this is all academic.

  Relevancy
  I think about this because I have pretty much stuck to low-level programming all of my life, mostly due to my interest in game and multimedia-type programming. But the trends in computing have favored many higher level languages and programming paradigms. I woke up one day and realized that the kind of work I often do — lower level stuff — is not very common.

  I’m not here to argue that low or high level is superior. You know I’m all about using the appropriate tool for the job. But I sometimes find myself caught between worlds, having the defend and explain one to the other.

  • On one hand, it’s not unusual for the multitudes of programmers working at the high level to gasp and wonder why I or anyone else would ever use C or assembly language for anything when there are so many beautiful high level languages. I patiently explain that those languages have to be written in some other language (at first) and that they need to run on some operating system and that most assuredly won’t be written in a high level language. For further reading, I refer them to Joel Spolsky’s great essay called Back to Basics which describes why it can be useful to know at least a little bit about how the computer does what it does at the lowest levels.
  • On the other hand, believe it or not, I sometimes have to defend the merits of high level languages to my low level brethren. I’ll often hear variations of, "Any program can be written in C. Using a high level language to achieve the same will create a slow and bloated solution." I try to explain that the trade-off in time to complete the programming task weighed against the often-negligible performance hit of what is often an I/O-bound operation in the first place makes it worthwhile to use the high level language for a wide variety of tasks.

    Or I just ignore them. That’s actually the best strategy.

• Metal Gear Solid VP3 Easter Egg

  4 août 2011, par Multimedia Mike — Game Hacking

  Metal Gear Solid : The Twin Snakes for the Nintendo GameCube is very heavy on the cutscenes. Most of them are animated in real-time but there are a bunch of clips — normally of a more photo-realistic nature — that the developers needed to compress using a conventional video codec. What did they decide to use for this task ? On2 VP3 (forerunner of Theora) in a custom transport format. This is only the second game I have seen in the wild that uses pure On2 VP3 (first was a horse game). Reimar and I sorted out most of the details sometime ago. I sat down today and wrote a FFmpeg / Libav demuxer for the format, mostly to prove to myself that I still could.

  Things went pretty smoothly. We suspected that there was an integer field that indicated the frame rate, but 18 fps is a bit strange. I kept fixating on a header field that read 0x41F00000. Where have I seen that number before ? Oh, of course — it’s the number 30.0 expressed as an IEEE 32-bit float. The 4XM format pulled the same trick.

  Hexadecimal Easter Egg
  I know I finished the game years ago but I really can’t recall any of the clips present in the samples directory. The file mgs1-60.vp3 contains a computer screen granting the player access and illustrates this with a hexdump. It looks something like this :

  
  
  

  Funny, there are only 22 bytes on a line when there should be 32 according to the offsets. But, leave it to me to try to figure out what the file type is, regardless. I squinted and copied the first 22 bytes into a file :

   1F 8B 08 00   85 E2 17 38   00 03 EC 3A   0D 78 54 D5
   38 00 03 EC   3A 0D
  

  And the answer to the big question :

  $ file mgsfile
  mgsfile : gzip compressed data, from Unix, last modified : Wed Oct 27 22:43:33 1999
  

  A gzip’d file from 1999. I don’t know why I find this stuff so interesting, but I do. I guess it’s no more and less strange than writing playback systems like this.

• Setting/Installing up OpenCV 2.4.6.1+ on Ubuntu 12.04.02

  30 mai 2016, par Damilola

  I had previously used OpenCV 2.4.5 with some certain configs and packages on Ubuntu 12.04.1 but had issues upgrading to OpenCV 2.4.6.1 on Ubuntu 12.04.2

  I would like to share some ideas (a compilation of noteworthy information gathered from several sources including SO, ubuntu.org, asklinux.org and many other ; and of course by trying several procedures)

  Below is what eventually got me through.

  NOTE : ensure you uninstall any previous installation of OpenCV, FFMpeg and other dependencies previously installed.

  STEP 1 (install ffmpeg and dependencies)

  ---

  # goto http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/
  
  # download the latest stable opencv such as 2.4.6.1 (http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.4.5/opencv-2.4.5.1.tar.gz/download) to current directory (such as home or ~/Document)
  
  # cd /opt
  
  # tar -xvf /OpenCV-2.4.6.1.tar.gz
  
  # cd OpenCV-2.4.6.1
  
  # create a foler under current dir (following previous step, this should be ), called prepare
  
  # cd prepare
  
  # Copy the following script to gedit and save as install.sh to current dir, this should be /prepare
  
  # Check corresponding url used in the script for latest versions of the package and replace as required
  
  # Open terminal and navigate to location used above
  
  # sudo chmod +x install.sh
  
  # ./install

  ---

  echo "Removing any pre-installed ffmpeg, x264, and other dependencies (not all the previously installed dependecies)"
  
  sudo apt-get remove ffmpeg x264 libx264-dev libvpx-dev librtmp0 librtmp-dev libopencv-dev
  
  sudo apt-get update
  
  
  
  arch=$(uname -m)
  
  if [ "$arch" == "i686" -o "$arch" == "i386" -o "$arch" == "i486" -o "$arch" == "i586" ]; then
  
  flag=0
  
  else
  
  flag=1
  
  fi
  
  
  
  echo "Installing Dependenices"
  
  sudo apt-get install autoconf automake make g++ curl cmake bzip2 python unzip \
  
    build-essential checkinstall git git-core libass-dev libgpac-dev \
  
    libsdl1.2-dev libtheora-dev libtool libva-dev libvdpau-dev libvorbis-dev libx11-dev \
  
    libxext-dev libxfixes-dev pkg-config texi2html zlib1g-dev
  
  
  
  echo "downloading yasm (assembler used by x264 and FFmpeg)"
  
  # use git or tarball (not both)
  
  wget http://www.tortall.net/projects/yasm/releases/yasm-1.2.0.tar.gz
  
  tar xzvf yasm-1.2.0.tar.gz
  
  cd yasm-1.2.0
  
  
  
  echo "installing yasm"
  
  ./configure
  
  make
  
  sudo make install
  
  cd ..
  
  
  
  echo 'READ NOTE BELOW which was extracted from http://wiki.serviio.org/doku.php?id=build_ffmpeg_linux'
  
  echo 'New version of x264 contains by default support of OpenCL. If not installed or without sense (example Ubuntu 12.04LTS on VMWare) add to configure additional option --disable-opencl. Without this option ffmpeg could not be configured (ERROR: libx264 not found).'
  
  
  
  echo "downloading x264 (H.264 video encoder)"
  
  # use git or tarball (not both)
  
  # git clone http://repo.or.cz/r/x264.git or
  
  git clone git://git.videolan.org/x264.git
  
  cd x264
  
  # wget ftp://ftp.videolan.org/pub/videolan/x264/snapshots/x264-snapshot-20130801-2245-stable.tar.bz2
  
  # tar -xvjf x264-snapshot-20130801-2245-stable.tar.bz2
  
  # cd x264-snapshot-20130801-2245-stable/
  
  
  
  echo "Installing x264"
  
  if [ $flag -eq 0 ]; then
  
  ./configure --enable-static --disable-opencl
  
  else
  
  ./configure --enable-shared --enable-pic --disable-opencl
  
  fi
  
  make
  
  sudo make install
  
  cd ..
  
  
  
  echo "downloading fdk-aac (AAC audio encoder)"
  
  # use git or tarball (not both)
  
  git clone --depth 1 git://github.com/mstorsjo/fdk-aac.git
  
  cd fdk-aac
  
  
  
  echo "installing fdk-aac"
  
  autoreconf -fiv
  
  ./configure --disable-shared
  
  make
  
  sudo make install
  
  cd ..
  
  
  
  echo "installing libmp3lame-dev (MP3 audio encoder.)"
  
  sudo apt-get install libmp3lame-dev
  
  
  
  echo "downloading libopus (Opus audio decoder and encoder.)"
  
  wget http://downloads.xiph.org/releases/opus/opus-1.0.3.tar.gz
  
  tar xzvf opus-1.0.3.tar.gz
  
  cd opus-1.0.3
  
  
  
  echo "installing libopus"
  
  ./configure --disable-shared
  
  make
  
  sudo make install
  
  cd ..
  
  
  
  echo "downloading libvpx VP8/VP9 video encoder and decoder)"
  
  # use git or tarball (not both)
  
  git clone --depth 1 http://git.chromium.org/webm/libvpx.git
  
  cd libvpx
  
  # wget http://webm.googlecode.com/files/libvpx-v1.1.0.tar.bz2 (this seems not to be update, but can still be used if the fedoraproject link below is not available))
  
  # wget http://pkgs.fedoraproject.org/repo/pkgs/libvpx/libvpx-v1.2.0.tar.bz2/400d7c940c5f9d394893d42ae5f463e6/libvpx-v1.2.0.tar.bz2
  
  # tar xvjf libvpx-v1.2.0.tar.bz2
  
  # cd libvpx-v1.2.0
  
  
  
  echo "installing libvpx"
  
  ./configure --disable-examples
  
  make
  
  sudo make install
  
  cd ..
  
  
  
  sudo ldconfig
  
  
  
  echo "downloading ffmpeg"
  
  # git clone http://repo.or.cz/r/ffmpeg.git
  
  git clone git://source.ffmpeg.org/ffmpeg.git
  
  cd ffmpeg/
  
  # wget http://ffmpeg.org/releases/ffmpeg-2.0.tar.bz2
  
  # tar -xvjf ffmpeg-2.0.tar.bz2
  
  # cd ffmpeg-2.0/
  
  
  
  echo "installing ffmpeg" 
  
  if [ $flag -eq 0 ]; then
  
  ./configure --enable-gpl --enable-libass --enable-libfdk-aac --enable-libopus --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-libvpx
  
  else
  
  ./configure --enable-gpl --enable-libass --enable-libfdk-aac --enable-libopus --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-libvpx --enable-shared
  
  fi
  
  
  
  make
  
  sudo make install
  
  hash -r
  
  
  
  cd .. # move up one level to prepare folder
  
  cd .. # move up one level to opencv folder
  
  
  
  echo "Checking to see if you're using your new ffmpeg"
  
  ffmpeg 2>&1 | head -n1
  
  
  
  sudo ldconfig

  STEP 2 (Install OpenCV and necessary packages)

  echo "Installing Dependenices"    
  
  sudo apt-get install libtiff4-dev libjpeg-dev libjasper-dev
  
  
  
  echo "installing Video I/O libraries, support for Firewire video cameras and video streaming libraries"
  
  sudo apt-get install libav-tools libavcodec-dev libavformat-dev libswscale-dev libdc1394-22-dev libxine-dev libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev libv4l-dev v4l-utils v4l-conf
  
  
  
  echo "installing the Python development environment and the Python Numerical library"
  
  sudo apt-get install python-dev python-numpy
  
  
  
  echo "installing the parallel code processing library (the Intel tbb library)"
  
  sudo apt-get install libtbb-dev
  
  
  
  echo "installing the Qt dev library"
  
  sudo apt-get install libqt4-dev libgtk2.0-dev
  
  
  
  echo "installing other dependencies (if need be it would upgrade current version of the packages)"
  
  sudo apt-get install patch subversion ruby librtmp0 librtmp-dev libfaac-dev libmp3lame-dev libopencore-amrnb-dev libopencore-amrwb-dev libvpx-dev libxvidcore-dev
  
  
  
  echo installing optional packages"
  
  sudo apt-get install libdc1394-utils libdc1394-22-dev libdc1394-22 libjpeg-dev libpng-dev libtiff-dev libjasper-dev

  STEP 3 (run ldconfig)

  # Open a new terminal window
  
  # Open /etc/ld.so.conf and check, 
  
  # if the paths "/usr/lib" and "/usr/local/lib" including the quote exist in the file. If not, add them manually or by
  
      sudo echo "/usr/local/lib" >> /etc/ld.so.conf
  
      sudo echo "/usr/lib" >> /etc/ld.so.conf
  
  # execute the following
  
      sudo ldconfig

  STEP 4a (Build & Install for OS Usage)

  # still ensure you haven't close the new terminal window open in STEP 3
  
  # execute the following
  
  mkdir os_build
  
  cd os_build
  
  cmake -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_NEW_PYTHON_SUPPORT=ON -DINSTALL_PYTHON_EXAMPLES=ON -DWITH_TBB=ON -DWITH_V4L=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DWITH_QT=ON -DWITH_OPENGL=ON -DWITH_OPENCL=ON -DWITH_EIGEN=ON -DWITH_OPENEXR=ON ..
  
  
  
      make
  
      sudo make install
  
  
  
  # add the following to user environment variable ~/.bashrc
  
      export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/lib
  
      export PKG_CONFIG_PATH=${PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig
  
  # execute the following
  
      sudo ldconfig
  
  # start to use and enjoy opencv, it should have been install into any of these locations
  
  #   /usr/local/include/opencv2, /usr/local/include/opencv, /usr/include/opencv, /usr/include/opencv2, /usr/local/share/opencv
  
  #   /usr/local/share/OpenCV, /usr/share/opencv, /usr/share/OpenCV, /usr/local/bin/opencv*, /usr/local/lib/libopencv*

  STEP 4b (Build for Java Usage) : OPTIONAL

  # still ensure you haven't close the new terminal window open in STEP 4
  
  # execute the following
  
      cd ..
  
      mkdir java_build
  
      cd java_build
  
      cmake -DCMAKE_BUILD_TYPE=RELEASE -DBUILD_SHARED_LIBS=OFF -DINSTALL_PYTHON_EXAMPLES=ON -DWITH_TBB=ON -DWITH_V4L=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DWITH_QT=ON -DWITH_OPENGL=ON -DWITH_OPENCL=ON -DWITH_EIGEN=ON -DWITH_OPENEXR=ON ..
  
  
  
      make
  
  
  
  # You can check the "java_build/bin" directory to locate the jar and libopencv_java.so file for your development
  
  # As stated in the docs, the Java bindings dynamic library is all-sufficient, i.e. doesn’t depend on other OpenCV libs, but includes all the OpenCV code inside

  STEP 5 (install v4l : Note : installing v4l-utils after opencv installation works for Ubuntu 12.04.2 & OpenCV 2.4.6.1)

  # still ensure you haven't close the new terminal window open in STEP 3
  
  # goto http://www.linuxtv.org/downloads/v4l-utils
  
  # download the latest v4l such as v4l-utils-0.9.5.tar.bz2
  
  # copy the downloaded file to the current terminal dir (following previous step, this should be /prepare)
  
  # execute the following
  
      tar -xvjf v4l-utils-0.9.5.tar.bz2
  
      cd v4l-utils-0.9.5/
  
      ./configure
  
      make
  
      sudo make install
  
      cd ..
  
      cd .. # (to go to )
  
      sudo ldconfig

  Worth Noting

  # To check the path where opencv & other lib files are stored, do:
  
  
  
  
  
  pkg-config --cflags opencv
  
  
  
      (output will come as)
  
      -I/usr/include/opencv
  
  
  
  
  
  
  
  pkg-config --libs opencv
  
  
  
      (output will come as)
  
      -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ --ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_flann
  
  
  
  # The above paths are needed to compile your opencv programs, as given in the next illustration.
  
  
  
  # write a simple C program to test, by saving below program in a file named DisplayImage.c
  
  
  
  #include 
  
      #include <opencv2></opencv2>highgui/highgui.hpp>
  
  
  
      int main(int argc, char *argv[]) {
  
          IplImage* img=0; /* pointer to an image */
  
          printf("Hello\n");
  
  
  
          if(argv[1] != 0)
  
              img = cvLoadImage(argv[1], 0); // 1 for color
  
          else
  
              printf("Enter filename\n");
  
  
  
          if(img != 0) {
  
              cvNamedWindow("Display", CV_WINDOW_AUTOSIZE); // create a window
  
              cvShowImage("Display", img); // show image in window
  
              cvWaitKey(0); // wait until user hits a key
  
              cvDestroyWindow("Display");
  
          }
  
          else
  
              printf("File not found\n");
  
  
  
          return 0;
  
      }
  
  
  
  # write a simple C++ program to test, by saving below program in a file named DisplayImage.cpp
  
  
  
  #include 
  
  #include <opencv2></opencv2>opencv.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  
  
  using namespace cv;
  
  
  
  int main( int argc, char** argv )
  
  {
  
    Mat image;
  
    image = imread( argv[1], 1 );
  
  
  
    if( argc != 2 || !image.data )
  
      {
  
        printf( "No image data \n" );
  
        return -1;
  
      }
  
  
  
    namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
  
    imshow( "Display Image", image );
  
  
  
    waitKey(0);
  
  
  
    return 0;
  
  }
  
  
  
  # To compile &amp; run :
  
  
  
  
  
  
  
  g++  `pkg-config --cflags --libs opencv` &amp;&amp; ./a.out img
  
  
  
  or
  
  
  
  
  
  
  
  g++ -I/usr/include/opencv -I/usr/local/include -lopencv_core -lopencv_highgui -lopencv_ml -lopencv_imgproc -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_flann -lopencv_nonfree  &amp;&amp; ./a.out img
  
  
  
  where “img” is the name of any image with extension within the same folder .
  
  You should be able to see “Hello” and the image in a different window.
  
  
  
  If this runs, Congrats! now you can run any C/C++ program with opencv lib.
  
  
  
  
  
  # Now lets simplify the above big command by making a shortcut for it:
  
  go to your local home directory(cd /home/) and open the .bashrc file using gedit(the file will be hidden). Append the following to the file:
  
  
  
  
  
  
  
  alias gcv="g++ -I/usr/include/opencv -I/usr/local/include -lopencv_core -lopencv_highgui -lopencv_ml -lopencv_imgproc -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_flann -lopencv_nonfree"
  
  
  
  and save. Close the terminal and open it again.(as this process requires relogin of the terminal)
  
  
  
  # Now, go to directory containing a sample program &amp; do
  
  
  
  
  
  
  
  gcv  &amp;&amp; ./a.out
  
  
  
  or
  
  
  
  
  
  
  
  gcv 
  
      ./a.out input_img.jpg

  As you can see the commands now become similar to $cc filename.c, $./a.out which are used normally for compiling and executing C/C++ programs.

  ---

  Some ways to check whether all lib files are installed-

  apt-cache search opencv

  returns :

  libcv-dev - Translation package for libcv-dev
  
  libcv2.3 - computer vision library - libcv* translation package
  
  libcvaux-dev - Translation package for libcvaux-dev
  
  libcvaux2.3 - computer vision library - libcvaux translation package
  
  libhighgui-dev - Translation package for libhighgui-dev
  
  libhighgui2.3 - computer vision library - libhighgui translation package
  
  libopencv-calib3d-dev - development files for libopencv-calib3d
  
  libopencv-calib3d2.3 - computer vision Camera Calibration library
  
  libopencv-contrib-dev - development files for libopencv-contrib
  
  libopencv-contrib2.3 - computer vision contrib library
  
  libopencv-core-dev - development files for libopencv-core
  
  libopencv-core2.3 - computer vision core library
  
  libopencv-dev - development files for opencv
  
  libopencv-features2d-dev - development files for libopencv-features2d
  
  libopencv-features2d2.3 - computer vision Feature Detection and Descriptor Extraction library
  
  libopencv-flann-dev - development files for libopencv-flann
  
  libopencv-flann2.3 - computer vision Clustering and Search in Multi-Dimensional spaces library
  
  libopencv-gpu-dev - development files for libopencv-gpu
  
  libopencv-gpu2.3 - computer vision GPU Processing library
  
  libopencv-highgui-dev - development files for libopencv-highgui
  
  libopencv-highgui2.3 - computer vision High-level GUI and Media I/O library
  
  libopencv-imgproc-dev - development files for libopencv-imgproc
  
  libopencv-imgproc2.3 - computer vision Image Processing library
  
  libopencv-legacy-dev - development files for libopencv-legacy
  
  libopencv-legacy2.3 - computer vision legacy library
  
  libopencv-ml-dev - development files for libopencv-ml
  
  libopencv-ml2.3 - computer vision Machine Learning library
  
  libopencv-objdetect-dev - development files for libopencv-objdetect
  
  libopencv-objdetect2.3 - computer vision Object Detection library
  
  libopencv-video-dev - development files for libopencv-video
  
  libopencv-video2.3 - computer vision Video analysis library
  
  opencv-doc - OpenCV documentation and examples
  
  python-opencv - Python bindings for the computer vision library