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• ffmpeg/libx264 C API : frames dropped from end of short MP4

  19 juillet 2017, par Blake McConnell

  In my C++ application, I am taking a series of JPEG images, manipulating their data using FreeImage, and then encoding the bitmaps as H264 using the ffmpeg/libx264 C API. The output is an MP4 which shows the series of 22 images at 12fps. My code is adapted from the "muxing" example that comes with ffmpeg C source code.

  My problem : no matter how I tune the codec parameters, a certain number of frames at the end of the sequence which are passed to the encoder do not appear in the final output. I’ve set the AVCodecContext parameters like this :

  //set context params
  
  ctx->codec_id = AV_CODEC_ID_H264;
  
  ctx->bit_rate = 4000 * 1000;
  
  ctx->width = _width;
  
  ctx->height = _height;
  
  ost->st->time_base = AVRational{ 1, 12 };
  
  ctx->time_base = ost->st->time_base;
  
  ctx->gop_size = 1;
  
  ctx->pix_fmt = AV_PIX_FMT_YUV420P;

  I have found that the higher the gop_size the more frames are dropped from the end of the video. I can also see from the output that, with this gop size (where I’m essentially directing that all output frames be I frames) that only 9 frames are written.

  I’m not sure why this is occurring. I experimented with encoding duplicate frames and making a much longer video. This resulted in no frames being dropped. I know with the ffmpeg command line tool there is a concatenation command that accomplishes what I am trying to do, but I’m not sure how to accomplish the same goal using the C API.

  Here’s the output I’m getting from the console :

  [libx264 @ 026d81c0] using cpu capabilities : MMX2 SSE2Fast SSSE3
  SSE4.2 AVX FMA3 BMI2 AVX2 [libx264 @ 026d81c0] profile High, level
  3.1 [libx264 @ 026d81c0] 264 - core 152 r2851 ba24899 - H.264/MPEG-4 AVC codec - Cop yleft 2003-2017 - http://www.videolan.org/x264.html -
  options : cabac=1 ref=1 deb lock=1:0:0 analyse=0x3:0x113 me=hex subme=7
  psy=1 psy_rd=1.00:0.00 mixed_ref=0 m e_range=16 chroma_me=1 trellis=1
  8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chro ma_qp_offset=-2
  threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1
  interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0
  keyint=1 ke yint_min=1 scenecut=40 intra_refresh=0 rc=abr mbtree=0
  bitrate=4000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4
  ip_ratio=1.40 aq=1:1.00 Output #0, mp4, to
  ’....\images\c411a991-46f6-400c-8bb0-77af3738559a.mp4’ :
  Stream #0:0 : Video : h264, yuv420p, 700x700, q=2-31, 4000 kb/s, 12 tbn

  [libx264 @ 026d81c0] frame I:9 Avg QP:17.83 size:111058 [libx264
  @ 026d81c0] mb I I16..4 : 1.9% 47.7% 50.5% [libx264 @ 026d81c0] final
  ratefactor : 19.14 [libx264 @ 026d81c0] 8x8 transform intra:47.7%
  [libx264 @ 026d81c0] coded y,uvDC,uvAC intra : 98.4% 96.9% 89.5%
  [libx264 @ 026d81c0] i16 v,h,dc,p : 64% 6% 2% 28% [libx264 @
  026d81c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu : 32% 15% 9% 5% 5% 6% 8%
  10% 10% [libx264 @ 026d81c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu : 28% 18%
  7% 6% 8% 8% 8% 9% 8% [libx264 @ 026d81c0] i8c dc,h,v,p : 43% 22%
  25% 10% [libx264 @ 026d81c0] kb/s:10661.53

  Code included below :

  MP4Writer.h

  #ifndef MPEG_WRITER
  
  #define MPEG_WRITER
  
  
  
  #include <iostream>
  
  #include <string>
  
  #include <vector>
  
  #include 
  
  extern "C" {
  
      #include <libavformat></libavformat>avformat.h>
  
      #include <libswscale></libswscale>swscale.h>
  
      #include <libswresample></libswresample>swresample.h>
  
      #include <libswscale></libswscale>swscale.h>
  
  }
  
  
  
  typedef struct OutputStream 
  
  {
  
      AVStream *st;
  
      AVCodecContext *enc;
  
  
  
      //pts of the next frame that will be generated
  
      int64_t next_pts;
  
      int samples_count;
  
  
  
      AVFrame *frame;
  
      AVFrame *tmp_frame;
  
  
  
      float t, tincr, tincr2;
  
  
  
      struct SwsContext *sws_ctx;
  
      struct SwrContext *swr_ctx;
  
  };
  
  
  
  class MP4Writer {
  
      public:
  
          MP4Writer();
  
          void Init();
  
          int16_t SetOutput( const std::string &amp; path );
  
          int16_t AddFrame( uint8_t * imgData );
  
          int16_t Write( std::vector<imgdata> &amp; imgData );
  
          int16_t Finalize();
  
          void SetHeight( const int height ) { _height = _width = height; } //assuming 1:1 aspect ratio
  
  
  
      private:
  
          int16_t AddStream( OutputStream * ost, AVFormatContext * formatCtx, AVCodec ** codec, enum AVCodecID codecId );
  
          int16_t OpenVideo( AVFormatContext * formatCtx, AVCodec *codec, OutputStream * ost, AVDictionary * optArg );
  
          static AVFrame * AllocPicture( enum AVPixelFormat pixFmt, int width, int height );
  
          static AVFrame * GetVideoFrame( uint8_t * imgData, OutputStream * ost, const int width, const int height );
  
          static int WriteFrame( AVFormatContext * formatCtx, const AVRational * timeBase, AVStream * stream, AVPacket * packet );
  
  
  
          int _width;
  
          int _height;
  
          OutputStream _ost;
  
          AVFormatContext * _formatCtx;
  
          AVDictionary * _dict;
  
  };
  
  
  
  #endif //MPEG_WRITER
  
  </imgdata></vector></string></iostream>

  MP4Writer.cpp

  #include 
  
  #include <algorithm>
  
  
  
  MP4Writer::MP4Writer()
  
  {
  
      _width = 0;
  
      _height = 0;
  
  }
  
  
  
  void MP4Writer::Init()
  
  {
  
      av_register_all();
  
  }
  
  
  
  /**
  
   sets up output stream for the specified path.
  
   note that the output format is deduced automatically from the file extension passed
  
   @param path: output file path
  
   @returns: -1 = output could not be deduced, -2 = invalid codec, -3 = error opening output file,
  
             -4 = error writing header
  
  */
  
  int16_t MP4Writer::SetOutput( const std::string &amp; path )
  
  {
  
      int error;
  
      AVCodec * codec;
  
      AVOutputFormat * format;
  
  
  
      _ost = OutputStream{}; //TODO reset state in a more focused way?
  
  
  
      //allocate output media context
  
      avformat_alloc_output_context2( &amp;_formatCtx, NULL, NULL, path.c_str() );
  
      if ( !_formatCtx ) {
  
          std::cout &lt;&lt; "could not deduce output format from file extension.  aborting" &lt;&lt; std::endl;
  
          return -1;
  
      }
  
      //set format
  
      format = _formatCtx->oformat;
  
      if ( format->video_codec != AV_CODEC_ID_NONE ) {
  
          AddStream( &amp;_ost, _formatCtx, &amp;codec, format->video_codec );
  
      }
  
      else {
  
          std::cout &lt;&lt; "there is no video codec set.  aborting" &lt;&lt; std::endl;
  
          return -2;
  
      }
  
  
  
      OpenVideo( _formatCtx, codec, &amp;_ost, _dict );
  
  
  
      av_dump_format( _formatCtx, 0, path.c_str(), 1 );
  
  
  
      //open output file
  
      if ( !( format->flags &amp; AVFMT_NOFILE )) {
  
          error = avio_open( &amp;_formatCtx->pb, path.c_str(), AVIO_FLAG_WRITE );
  
          if ( error &lt; 0 ) {
  
              std::cout &lt;&lt; "there was an error opening output file " &lt;&lt; path &lt;&lt; ".  aborting" &lt;&lt; std::endl;
  
              return -3;
  
          }
  
      }
  
  
  
      //write header
  
      error = avformat_write_header( _formatCtx, &amp;_dict );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "an error occurred writing header. aborting" &lt;&lt; std::endl;
  
          return -4;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  /**
  
   initialize the output stream
  
   @param ost: the output stream
  
   @param formatCtx: the context format
  
   @param codec: the output codec
  
   @param codec: the ffmpeg enumerated id of the codec
  
   @returns: -1 = encoder not found, -2 = stream could not be allocated, -3 = encoding context could not be allocated
  
  */
  
  int16_t MP4Writer::AddStream( OutputStream * ost, AVFormatContext * formatCtx, AVCodec ** codec, enum AVCodecID codecId )
  
  {
  
      AVCodecContext * ctx; //TODO not sure why this is here, could just set ost->enc directly
  
      int i;
  
  
  
      //detect the encoder
  
      *codec = avcodec_find_encoder( codecId );
  
      if ( (*codec) == NULL ) {
  
          std::cout &lt;&lt; "could not find encoder.  aborting" &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      //allocate stream
  
      ost->st = avformat_new_stream( formatCtx, NULL );
  
      if ( ost->st == NULL ) {
  
          std::cout &lt;&lt; "could not allocate stream.  aborting" &lt;&lt; std::endl;
  
          return -2;
  
      }
  
  
  
      //allocate encoding context
  
      ost->st->id = formatCtx->nb_streams - 1;
  
      ctx = avcodec_alloc_context3( *codec );
  
      if ( ctx == NULL ) {
  
          std::cout &lt;&lt; "could not allocate encoding context.  aborting" &lt;&lt; std::endl;
  
          return -3;
  
      }
  
  
  
      ost->enc = ctx;
  
  
  
      //set context params
  
      ctx->codec_id = AV_CODEC_ID_H264;
  
      ctx->bit_rate = 4000 * 1000;
  
      ctx->width = _width;
  
      ctx->height = _height;
  
      ost->st->time_base = AVRational{ 1, 12 };
  
      ctx->time_base = ost->st->time_base;
  
      ctx->gop_size = 1;
  
      ctx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      //if neccesary, set stream headers and formats separately
  
      if ( formatCtx->oformat->flags &amp; AVFMT_GLOBALHEADER ) {
  
          std::cout &lt;&lt; "setting stream and headers to be separate" &lt;&lt; std::endl;
  
          ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  /**
  
   open the video for writing
  
   @param formatCtx: the format context
  
   @param codec: output codec
  
   @param ost: output stream
  
   @param optArg: dictionary
  
   @return: -1 = error opening codec, -2 = allocate new frame, -3 = copy stream params
  
  */
  
  int16_t MP4Writer::OpenVideo( AVFormatContext * formatCtx, AVCodec *codec, OutputStream * ost, AVDictionary * optArg )
  
  {
  
      int error;
  
      AVCodecContext * ctx = ost->enc;
  
      AVDictionary * dict = NULL;
  
      av_dict_copy( &amp;dict, optArg, 0 );
  
  
  
      //open codec
  
      error = avcodec_open2( ctx, codec, &amp;dict );
  
      av_dict_free( &amp;dict );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "there was an error opening the codec.  aborting" &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      //allocate new frame
  
      ost->frame = AllocPicture( ctx->pix_fmt, ctx->width, ctx->height );
  
      if ( ost->frame == NULL ) {
  
          std::cout &lt;&lt; "there was an error allocating a new frame.  aborting" &lt;&lt; std::endl;
  
          return -2;
  
      }
  
  
  
      //copy steam params
  
      error = avcodec_parameters_from_context( ost->st->codecpar, ctx );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "could not copy stream parameters.  aborting" &lt;&lt; std::endl;
  
          return -3;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  /**
  
   allocate a new frame
  
   @param pixFmt: ffmpeg enumerated pixel format
  
   @param width: output width
  
   @param height: output height
  
   @returns: an inititalized frame
  
  */
  
  AVFrame * MP4Writer::AllocPicture( enum AVPixelFormat pixFmt, int width, int height )
  
  {
  
      AVFrame * picture;
  
      int error;
  
  
  
      //allocate the frame
  
      picture = av_frame_alloc();
  
      if ( picture == NULL ) {
  
          std::cout &lt;&lt; "there was an error allocating the picture" &lt;&lt; std::endl;
  
          return NULL;
  
      }
  
  
  
      picture->format = pixFmt;
  
      picture->width = width;
  
      picture->height = height;
  
  
  
      //allocate the frame's data buffer
  
      error = av_frame_get_buffer( picture, 32 );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "could not allocate frame data" &lt;&lt; std::endl;
  
          return NULL;
  
      }
  
      picture->pts = 0;
  
      return picture;
  
  }
  
  
  
  /**
  
   convert raw RGB buffer to YUV frame
  
   @return: frame that contains image data
  
  */
  
  AVFrame * MP4Writer::GetVideoFrame( uint8_t * imgData, OutputStream * ost, const int width, const int height )
  
  {
  
      int error;
  
      AVCodecContext * ctx = ost->enc;
  
  
  
      //prepare the frame
  
      error = av_frame_make_writable( ost->frame );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "could not make frame writeable" &lt;&lt; std::endl;
  
          return NULL;
  
      }
  
  
  
      //TODO set this context one time per run, or even better, one time at init
  
      //convert RGB to YUV
  
      struct SwsContext* fooContext = sws_getContext( width, height, AV_PIX_FMT_BGR24, 
  
          width, height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL );
  
      int inLinesize[1] = { 3 * width }; // RGB stride
  
      uint8_t * inData[1] = { imgData };
  
      int sliceHeight = sws_scale( fooContext, inData, inLinesize, 0, height, ost->frame->data, ost->frame->linesize );
  
      sws_freeContext( fooContext );
  
  
  
      ost->frame->pts = ost->next_pts++;
  
      //TODO does the frame need to be returned here as it is available at the class level?
  
      return ost->frame;
  
  }
  
  
  
  /**
  
   write frame to file
  
   @param formatCtx: the output format context
  
   @param timeBase: the framerate
  
   @param stream: output stream
  
   @param packet: data packet
  
   @returns: see return values for av_interleaved_write_frame
  
  */
  
  int MP4Writer::WriteFrame( AVFormatContext * formatCtx, const AVRational * timeBase, AVStream * stream, AVPacket * packet )
  
  {
  
      av_packet_rescale_ts( packet, *timeBase, stream->time_base );
  
      packet->stream_index = stream->index;
  
  
  
      //write compressed file to media file
  
      return av_interleaved_write_frame( formatCtx, packet );
  
  }
  
  
  
  int16_t MP4Writer::Write( std::vector<imgdata> &amp; imgData )
  
  {
  
      int16_t errorCount = 0;
  
      int16_t retVal = 0;
  
      bool countingUp = true;
  
      size_t i = 0;
  
      while ( true ) {
  
          //don't show first frame again when counting back down
  
          if ( !countingUp &amp;&amp; i == 0 ) {
  
              break;
  
          }
  
          uint8_t * pixels = imgData[i].GetBits( imgData[i].mp4Input );
  
          AddFrame( pixels );
  
  
  
          //handle inc/dec without repeating last frame
  
          if ( countingUp ) {
  
              if ( i == imgData.size() -1 ) {
  
                  countingUp = false;
  
                  i--;
  
              }
  
              else {
  
                  i++;
  
              }
  
          }
  
          else {
  
              i--;
  
          }
  
      }
  
      Finalize();
  
      return 0; //TODO return error code
  
  }
  
  
  
  /**
  
   add another frame to output video
  
   @param imgData: the raw image data
  
   @returns -1 = error encoding video frame, -2 = error writing frame
  
  */
  
  int16_t MP4Writer::AddFrame( uint8_t * imgData )
  
  {
  
      int error;
  
      AVCodecContext * ctx;
  
      AVFrame * frame;
  
      int gotPacket = 0;
  
      AVPacket pkt = { 0 };
  
  
  
      ctx = _ost.enc;
  
      av_init_packet( &amp;pkt );
  
  
  
      frame = GetVideoFrame( imgData, &amp;_ost, _width, _height );
  
  
  
      //encode the image
  
      error = avcodec_encode_video2( ctx, &amp;pkt, frame, &amp;gotPacket );
  
      if ( error &lt; 0 ) {
  
          std::cout &lt;&lt; "there was an error encoding the video frame" &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      //write the frame.  NOTE: this doesn't kick in until the encoder has received a certain number of frames
  
      if ( gotPacket ) {
  
          error = WriteFrame( _formatCtx, &amp;ctx->time_base, _ost.st, &amp;pkt );
  
          if ( error &lt; 0 ) {
  
              std::cout &lt;&lt; "the video frame could not be written" &lt;&lt; std::endl;
  
              return -2;
  
          }
  
      }
  
      return 0;
  
  }
  
  
  
  /**
  
   finalize output video and cleanup
  
  */
  
  int16_t MP4Writer::Finalize()
  
  {
  
      av_write_trailer( _formatCtx );
  
      avcodec_free_context( &amp;_ost.enc );
  
      av_frame_free( &amp;_ost.frame);
  
      av_frame_free( &amp;_ost.tmp_frame );
  
      avio_closep( &amp;_formatCtx->pb );
  
      avformat_free_context( _formatCtx );
  
      sws_freeContext( _ost.sws_ctx );
  
      swr_free( &amp;_ost.swr_ctx);
  
      return 0;
  
  }
  
  </imgdata></algorithm>

  usage

  #include 
  
  #include 
  
  #include <vector>
  
  
  
  struct ImgData
  
  {
  
      unsigned int width;
  
      unsigned int height;
  
      std::string path;
  
      FIBITMAP * mp4Input;
  
  
  
      uint8_t * GetBits( FIBITMAP * bmp ) { return FreeImage_GetBits( bmp ); }
  
  };
  
  
  
  int main()
  
  {
  
       std::vector<imgdata> imgDataVec;
  
       //load images and push to imgDataVec
  
       MP4Writer mp4Writer;
  
       mp4Writer.SetHeight( 1200 ); //assumes 1:1 aspect ratio
  
       mp4Writer.Init();
  
       mp4Writer.SetOutput( "test.mp4" );
  
       mp4Writer.Write( imgDataVec );
  
  }
  
  </imgdata></vector>

• trying to make OpenCV 3.2.0 work with virtualenv

  24 juillet 2017, par lollercoaster

  I’m on Ubuntu 16.04 with Python 2.7 and virtualenv & virtualenvwrapper.

  By following this guide I managed to get the following script working with my system Python2.7 which has cv2 globally installed.

  I used this script to install it :

  ######################################
  
  # INSTALL OPENCV ON UBUNTU OR DEBIAN #
  
  ######################################
  
  
  
  # |         THIS SCRIPT IS TESTED CORRECTLY ON         |
  
  # |----------------------------------------------------|
  
  # | OS             | OpenCV       | Test | Last test   |
  
  # |----------------|--------------|------|-------------|
  
  # | Ubuntu 16.04.2 | OpenCV 3.2.0 | OK   | 20 May 2017 |
  
  # | Debian 8.8     | OpenCV 3.2.0 | OK   | 20 May 2017 |
  
  # | Debian 9.0     | OpenCV 3.2.0 | OK   | 25 Jun 2017 |
  
  
  
  # 1. KEEP UBUNTU OR DEBIAN UP TO DATE
  
  
  
  sudo apt-get -y update
  
  sudo apt-get -y upgrade
  
  sudo apt-get -y dist-upgrade
  
  sudo apt-get -y autoremove
  
  
  
  
  
  # 2. INSTALL THE DEPENDENCIES
  
  
  
  # Build tools:
  
  sudo apt-get install -y build-essential cmake
  
  
  
  # GUI (if you want to use GTK instead of Qt, replace 'qt5-default' with 'libgtkglext1-dev' and remove '-DWITH_QT=ON' option in CMake):
  
  sudo apt-get install -y qt5-default libvtk6-dev
  
  
  
  # Media I/O:
  
  sudo apt-get install -y zlib1g-dev libjpeg-dev libwebp-dev libpng-dev libtiff5-dev libjasper-dev libopenexr-dev libgdal-dev
  
  
  
  # Video I/O:
  
  sudo apt-get install -y libdc1394-22-dev libavcodec-dev libavformat-dev libswscale-dev libtheora-dev libvorbis-dev libxvidcore-dev libx264-dev yasm libopencore-amrnb-dev libopencore-amrwb-dev libv4l-dev libxine2-dev
  
  
  
  # Parallelism and linear algebra libraries:
  
  sudo apt-get install -y libtbb-dev libeigen3-dev
  
  
  
  # Python:
  
  sudo apt-get install -y python-dev python-tk python-numpy python3-dev python3-tk python3-numpy
  
  
  
  # Documentation:
  
  sudo apt-get install -y doxygen
  
  
  
  # UI stuff
  
  sudo apt-get install libgtk-3-dev libatlas-base-dev gfortran
  
  
  
  
  
  # 3. INSTALL THE LIBRARY (YOU CAN CHANGE '3.2.0' FOR THE LAST STABLE VERSION)
  
  sudo apt-get install -y unzip wget
  
  
  
  # opencv contrib
  
  wget https://github.com/opencv/opencv_contrib/archive/3.2.0.zip -O opencv_contrib-3.2.0.zip
  
  unzip opencv_contrib-3.2.0.zip
  
  rm opencv_contrib-3.2.0.zip
  
  
  
  # opencv
  
  wget https://github.com/opencv/opencv/archive/3.2.0.zip
  
  unzip 3.2.0.zip
  
  rm 3.2.0.zip
  
  mv opencv-3.2.0 OpenCV-3.2.0
  
  cd OpenCV-3.2.0
  
  
  
  mkdir build
  
  cd build
  
  cmake -D WITH_QT=ON \
  
      -D WITH_OPENGL=ON \
  
      -D FORCE_VTK=ON \
  
      -D WITH_TBB=ON \
  
      -D WITH_GDAL=ON \
  
      -D WITH_XINE=ON \
  
      -D BUILD_EXAMPLES=ON \
  
      -D INSTALL_PYTHON_EXAMPLES=ON \
  
      -D ENABLE_PRECOMPILED_HEADERS=OFF \
  
      -D BUILD_NEW_PYTHON_SUPPORT=ON \
  
      ..
  
  
  
  make -j4
  
  sudo make install
  
  sudo ldconfig
  
  
  
  
  
  # 4. EXECUTE SOME OPENCV EXAMPLES AND COMPILE A DEMONSTRATION
  
  
  
  # To complete this step, please visit 'http://milq.github.io/install-opencv-ubuntu-debian'.

  The following script below works great with that system-wide installation :

  import cv2
  
  
  
  img = cv2.imread('some_img.jpg')

  Though this one doesn’t - even the system Python can’t read videos for some reason...

  import cv2
  
  
  
  video_capture = cv2.VideoCapture(0)
  
  ret, frame = video_capture.read()
  
  print ret  # always False

  but I want it to work with my virtualenv. So I recompiled OpenCV with :

  cmake -D WITH_QT=ON \
  
      -D WITH_OPENGL=ON \
  
      -D FORCE_VTK=ON \
  
      -D WITH_TBB=ON \
  
      -D WITH_GDAL=ON \
  
      -D WITH_XINE=ON \
  
      -D BUILD_EXAMPLES=ON \
  
      -D INSTALL_PYTHON_EXAMPLES=ON \
  
      -D ENABLE_PRECOMPILED_HEADERS=OFF \
  
      -D BUILD_NEW_PYTHON_SUPPORT=ON \
  
      -D OPENCV_EXTRA_MODULES_PATH=/home/me/code/myproject/opencv_contrib-3.2.0/modules \
  
      -D PYTHON_EXECUTABLE=~/.envs/myenv/bin/python \
  
      ..
  
  
  
  make -j4
  
  sudo make install
  
  sudo ldconfig

  Here’s the CMake log :

  -- Found VTK ver. 6.2.0 (usefile: /usr/lib/cmake/vtk-6.2/UseVTK.cmake)
  
  -- Caffe:   NO
  
  -- Protobuf:   YES
  
  -- Glog:   NO
  
  -- freetype2:   YES
  
  -- harfbuzz:    YES
  
  -- Module opencv_sfm disabled because the following dependencies are not found: Glog/Gflags
  
  -- freetype2:   YES
  
  -- harfbuzz:    YES
  
  -- Checking for modules 'tesseract;lept'
  
  --   No package 'tesseract' found
  
  --   No package 'lept' found
  
  -- Tesseract:   NO
  
  -- Check contents of vgg_generated_48.i ...
  
  -- Check contents of vgg_generated_64.i ...
  
  -- Check contents of vgg_generated_80.i ...
  
  -- Check contents of vgg_generated_120.i ...
  
  -- Check contents of boostdesc_bgm.i ...
  
  -- Check contents of boostdesc_bgm_bi.i ...
  
  -- Check contents of boostdesc_bgm_hd.i ...
  
  -- Check contents of boostdesc_binboost_064.i ...
  
  -- Check contents of boostdesc_binboost_128.i ...
  
  -- Check contents of boostdesc_binboost_256.i ...
  
  -- Check contents of boostdesc_lbgm.i ...
  
  -- 
  
  -- General configuration for OpenCV 3.2.0 =====================================
  
  --   Version control:               817bd7b-dirty
  
  -- 
  
  --   Extra modules:
  
  --     Location (extra):            /home/me/code/myproject/opencv_contrib-3.2.0/modules
  
  --     Version control (extra):     817bd7b-dirty
  
  -- 
  
  --   Platform:
  
  --     Timestamp:                   2017-07-20T18:25:26Z
  
  --     Host:                        Linux 4.8.0-58-generic x86_64
  
  --     CMake:                       3.5.1
  
  --     CMake generator:             Unix Makefiles
  
  --     CMake build tool:            /usr/bin/make
  
  --     Configuration:               Release
  
  -- 
  
  --   C/C++:
  
  --     Built as dynamic libs?:      YES
  
  --     C++ Compiler:                /usr/bin/c++  (ver 5.4.0)
  
  --     C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
  
  --     C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
  
  --     C Compiler:                  /usr/bin/cc
  
  --     C flags (Release):           -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
  
  --     C flags (Debug):             -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
  
  --     Linker flags (Release):
  
  --     Linker flags (Debug):
  
  --     ccache:                      NO
  
  --     Precompiled headers:         NO
  
  --     Extra dependencies:          Qt5::Test Qt5::Concurrent Qt5::OpenGL /usr/lib/x86_64-linux-gnu/libwebp.so /usr/lib/x86_64-linux-gnu/libjasper.so /usr/lib/x86_64-linux-gnu/libImath.so /usr/lib/x86_64-linux-gnu/libIlmImf.so /usr/lib/x86_64-linux-gnu/libIex.so /usr/lib/x86_64-linux-gnu/libHalf.so /usr/lib/x86_64-linux-gnu/libIlmThread.so /usr/lib/libgdal.so dc1394 xine avcodec-ffmpeg avformat-ffmpeg avutil-ffmpeg swscale-ffmpeg Qt5::Core Qt5::Gui Qt5::Widgets /usr/lib/x86_64-linux-gnu/hdf5/serial/lib/libhdf5.so /usr/lib/x86_64-linux-gnu/libpthread.so /usr/lib/x86_64-linux-gnu/libsz.so /usr/lib/x86_64-linux-gnu/libdl.so /usr/lib/x86_64-linux-gnu/libm.so vtkRenderingOpenGL vtkImagingHybrid vtkIOImage vtkCommonDataModel vtkCommonMath vtkCommonCore vtksys vtkCommonMisc vtkCommonSystem vtkCommonTransforms vtkCommonExecutionModel vtkDICOMParser vtkIOCore /usr/lib/x86_64-linux-gnu/libz.so vtkmetaio /usr/lib/x86_64-linux-gnu/libjpeg.so /usr/lib/x86_64-linux-gnu/libpng.so /usr/lib/x86_64-linux-gnu/libtiff.so vtkImagingCore vtkRenderingCore vtkCommonColor vtkFiltersExtraction vtkFiltersCore vtkFiltersGeneral vtkCommonComputationalGeometry vtkFiltersStatistics vtkImagingFourier vtkalglib vtkFiltersGeometry vtkFiltersSources vtkInteractionStyle vtkRenderingLOD vtkFiltersModeling vtkIOPLY vtkIOGeometry /usr/lib/x86_64-linux-gnu/libjsoncpp.so vtkFiltersTexture vtkRenderingFreeType /usr/lib/x86_64-linux-gnu/libfreetype.so vtkftgl vtkIOExport vtkRenderingAnnotation vtkImagingColor vtkRenderingContext2D vtkRenderingGL2PS vtkRenderingContextOpenGL /usr/lib/libgl2ps.so vtkRenderingLabel dl m pthread rt /usr/lib/x86_64-linux-gnu/libGLU.so /usr/lib/x86_64-linux-gnu/libGL.so tbb
  
  --     3rdparty dependencies:       libprotobuf
  
  -- 
  
  --   OpenCV modules:
  
  --     To be built:                 core flann hdf imgproc ml photo reg surface_matching video viz dnn freetype fuzzy imgcodecs shape videoio highgui objdetect plot superres ts xobjdetect xphoto bgsegm bioinspired dpm face features2d line_descriptor saliency text calib3d ccalib cvv datasets rgbd stereo tracking videostab xfeatures2d ximgproc aruco optflow phase_unwrapping stitching structured_light java python2 python3
  
  --     Disabled:                    world contrib_world
  
  --     Disabled by dependency:      -
  
  --     Unavailable:                 cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cnn_3dobj matlab sfm
  
  -- 
  
  --   GUI: 
  
  --     QT 5.x:                      YES (ver 5.5.1)
  
  --     QT OpenGL support:           YES (Qt5::OpenGL 5.5.1)
  
  --     OpenGL support:              YES (/usr/lib/x86_64-linux-gnu/libGLU.so /usr/lib/x86_64-linux-gnu/libGL.so)
  
  --     VTK support:                 YES (ver 6.2.0)
  
  -- 
  
  --   Media I/O: 
  
  --     ZLib:                        /usr/lib/x86_64-linux-gnu/libz.so (ver 1.2.8)
  
  --     JPEG:                        /usr/lib/x86_64-linux-gnu/libjpeg.so (ver )
  
  --     WEBP:                        /usr/lib/x86_64-linux-gnu/libwebp.so (ver encoder: 0x0202)
  
  --     PNG:                         /usr/lib/x86_64-linux-gnu/libpng.so (ver 1.2.54)
  
  --     TIFF:                        /usr/lib/x86_64-linux-gnu/libtiff.so (ver 42 - 4.0.6)
  
  --     JPEG 2000:                   /usr/lib/x86_64-linux-gnu/libjasper.so (ver 1.900.1)
  
  --     OpenEXR:                     /usr/lib/x86_64-linux-gnu/libImath.so /usr/lib/x86_64-linux-gnu/libIlmImf.so /usr/lib/x86_64-linux-gnu/libIex.so /usr/lib/x86_64-linux-gnu/libHalf.so /usr/lib/x86_64-linux-gnu/libIlmThread.so (ver 2.2.0)
  
  --     GDAL:                        /usr/lib/libgdal.so
  
  --     GDCM:                        NO
  
  -- 
  
  --   Video I/O:
  
  --     DC1394 1.x:                  NO
  
  --     DC1394 2.x:                  YES (ver 2.2.4)
  
  --     FFMPEG:                      YES
  
  --       avcodec:                   YES (ver 56.60.100)
  
  --       avformat:                  YES (ver 56.40.101)
  
  --       avutil:                    YES (ver 54.31.100)
  
  --       swscale:                   YES (ver 3.1.101)
  
  --       avresample:                NO
  
  --     GStreamer:                   NO
  
  --     OpenNI:                      NO
  
  --     OpenNI PrimeSensor Modules:  NO
  
  --     OpenNI2:                     NO
  
  --     PvAPI:                       NO
  
  --     GigEVisionSDK:               NO
  
  --     Aravis SDK:                  NO
  
  --     UniCap:                      NO
  
  --     UniCap ucil:                 NO
  
  --     V4L/V4L2:                    NO/YES
  
  --     XIMEA:                       NO
  
  --     Xine:                        YES (ver 1.2.6)
  
  --     gPhoto2:                     NO
  
  -- 
  
  --   Parallel framework:            TBB (ver 4.4 interface 9002)
  
  -- 
  
  --   Other third-party libraries:
  
  --     Use IPP:                     9.0.1 [9.0.1]
  
  --          at:                     /home/me/code/myproject/OpenCV-3.2.0/build/3rdparty/ippicv/ippicv_lnx
  
  --     Use IPP Async:               NO
  
  --     Use VA:                      NO
  
  --     Use Intel VA-API/OpenCL:     NO
  
  --     Use Lapack:                  NO
  
  --     Use Eigen:                   YES (ver 3.2.92)
  
  --     Use Cuda:                    NO
  
  --     Use OpenCL:                  YES
  
  --     Use OpenVX:                  NO
  
  --     Use custom HAL:              NO
  
  -- 
  
  --   OpenCL:                        <dynamic loading="loading" of="of" opencl="opencl" library="library">
  
  --     Include path:                /home/me/code/myproject/OpenCV-3.2.0/3rdparty/include/opencl/1.2
  
  --     Use AMDFFT:                  NO
  
  --     Use AMDBLAS:                 NO
  
  -- 
  
  --   Python 2:
  
  --     Interpreter:                 /home/me/.envs/myenv/bin/python (ver 2.7.12)
  
  --     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython2.7.so (ver 2.7.12)
  
  --     numpy:                       /home/me/.envs/myenv/local/lib/python2.7/site-packages/numpy/core/include (ver 1.13.1)
  
  --     packages path:               lib/python2.7/site-packages
  
  -- 
  
  --   Python 3:
  
  --     Interpreter:                 /usr/bin/python3 (ver 3.5.2)
  
  --     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython3.5m.so (ver 3.5.2)
  
  --     numpy:                       /usr/lib/python3/dist-packages/numpy/core/include (ver 1.11.0)
  
  --     packages path:               lib/python3.5/dist-packages
  
  -- 
  
  --   Python (for build):            /home/me/.envs/myenv/bin/python
  
  -- 
  
  --   Java:
  
  --     ant:                         /usr/bin/ant (ver 1.9.6)
  
  --     JNI:                         /usr/lib/jvm/default-java/include /usr/lib/jvm/default-java/include/linux /usr/lib/jvm/default-java/include
  
  --     Java wrappers:               YES
  
  --     Java tests:                  YES
  
  -- 
  
  --   Matlab:                        Matlab not found or implicitly disabled
  
  -- 
  
  --   Documentation:
  
  --     Doxygen:                     /usr/bin/doxygen (ver 1.8.11)
  
  -- 
  
  --   Tests and samples:
  
  --     Tests:                       YES
  
  --     Performance tests:           YES
  
  --     C/C++ Examples:              YES
  
  -- 
  
  --   Install path:                  /usr/local
  
  -- 
  
  --   cvconfig.h is in:              /home/me/code/myproject/OpenCV-3.2.0/build
  
  -- -----------------------------------------------------------------
  
  -- 
  
  </dynamic>

  Unfortunately, while this works and I can import cv2 in the shell, it cannot read video using the above script, probably due to incorrect compilation or linking of ffmpeg ? The confusing part is the system-wide installation of OpenCV works fine, even without ffmpeg installed !

  What am I doing wrong ? How can I get OpenCV working with a virtualenv ?

  ====

  EDIT : Running the C++ video writing example has this result :

  $ cd /home/me/code/myproject/OpenCV-3.2.0/build/bin
  
  $ ./cpp-tutorial-video-write ../../samples/data/vtest.avi R Y
  
  ------------------------------------------------------------------------------
  
  This program shows how to write video files.
  
  You can extract the R or G or B color channel of the input video.
  
  Usage:
  
  ./video-write  [ R | G | B] [Y | N]
  
  ------------------------------------------------------------------------------
  
  
  
  OpenCV: FFMPEG: tag 0xffffffff/'����' is not found (format 'avi / AVI (Audio Video Interleaved)')'
  
  
  
  (cpp-tutorial-video-write:19523): GStreamer-CRITICAL **: gst_element_make_from_uri: assertion 'gst_uri_is_valid (uri)' failed
  
  OpenCV Error: Unsupported format or combination of formats (Gstreamer Opencv backend does not support this codec.) in CvVideoWriter_GStreamer::open, file /home/me/code/myproject/OpenCV-3.2.0/modules/videoio/src/cap_gstreamer.cpp, line 1388
  
  VIDEOIO(cvCreateVideoWriter_GStreamer(filename, fourcc, fps, frameSize, is_color)): raised OpenCV exception:
  
  
  
  /home/me/code/myproject/OpenCV-3.2.0/modules/videoio/src/cap_gstreamer.cpp:1388: error: (-210) Gstreamer Opencv backend does not support this codec. in function CvVideoWriter_GStreamer::open
  
  
  
  Could not open the output video for write: ../../samples/data/vtest.avi

  And the opencv_test_videoio unit test reports the following : https://pastebin.com/q4mf224Q

  However, running the c++ video starter example DOES work, with the following command and output, I can see the webcam working and streaming video in the highgui interface :

  $ ./cpp-example-videocapture_starter 0
  
  VIDEOIO ERROR: V4L: device 0: Unable to query number of channels
  
  (ERROR)icvOpenAVI_XINE(): Unable to initialize video driver.
  
  GStreamer: Error opening bin: no element "0"
  
  press space to save a picture. q or esc to quit
  
  init done
  
  opengl support available

• Video rotating to left by 90 degree when converted using ffmpeg

  15 juillet 2017, par Herdesh Verma

  I developed a below code :

  extern "C"
  
  {
  
  #include <libavutil></libavutil>imgutils.h>
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavutil></libavutil>mathematics.h>
  
  #include <libavutil></libavutil>samplefmt.h>
  
  #include <libavutil></libavutil>timestamp.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavfilter></libavfilter>avfiltergraph.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  }
  
  #include 
  
  static AVFormatContext *fmt_ctx = NULL;
  
  
  
  static int frame_index = 0;
  
  
  
  static int j = 0, nbytes=0;
  
  uint8_t *video_outbuf = NULL;
  
  static AVPacket *pAVPacket=NULL;
  
  static int value=0;
  
  static AVFrame *pAVFrame=NULL;
  
  static AVFrame *outFrame=NULL;
  
  static AVStream *video_st=NULL;
  
  static AVFormatContext *outAVFormatContext=NULL;
  
  static AVCodec *outAVCodec=NULL;
  
  static AVOutputFormat *output_format=NULL;
  
  static AVCodecContext *video_dec_ctx = NULL, *audio_dec_ctx;
  
  static AVCodecContext *outAVCodecContext=NULL;
  
  static int width, height;
  
  static enum AVPixelFormat pix_fmt;
  
  static AVStream *video_stream = NULL, *audio_stream = NULL;
  
  static const char *src_filename = NULL;
  
  static const char *video_dst_filename = NULL;
  
  static const char *audio_dst_filename = NULL;
  
  static FILE *video_dst_file = NULL;
  
  static FILE *audio_dst_file = NULL;
  
  static uint8_t *video_dst_data[4] = {NULL};
  
  static int      video_dst_linesize[4];
  
  static int video_dst_bufsize;
  
  static int video_stream_idx = -1, audio_stream_idx = -1;
  
  static AVPacket *pkt=NULL;
  
  static AVPacket *pkt1=NULL;
  
  static AVFrame *frame = NULL;
  
  //static AVPacket pkt;
  
  static int video_frame_count = 0;
  
  static int audio_frame_count = 0;
  
  static int refcount = 0;
  
  AVCodec *codec;
  
  static struct SwsContext *sws_ctx;
  
  AVCodecContext *c= NULL;
  
   int i, out_size, size, x, y, outbuf_size;
  
   AVFrame *picture;
  
   uint8_t *outbuf, *picture_buf;
  
  int video_outbuf_size;
  
  int w, h;
  
  AVPixelFormat pixFmt;
  
  uint8_t *data[4];
  
  int linesize[4];
  
  
  
  static int open_codec_context(int *stream_idx,
  
                            AVCodecContext **dec_ctx, AVFormatContext 
  
  *fmt_ctx, enum AVMediaType type)
  
  {
  
  int ret, stream_index;
  
  AVStream *st;
  
  AVCodec *dec = NULL;
  
  AVDictionary *opts = NULL;
  
  ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
  
  if (ret &lt; 0) {
  
      printf("Could not find %s stream in input file '%s'\n",
  
              av_get_media_type_string(type), src_filename);
  
      return ret;
  
  } else {
  
      stream_index = ret;
  
      st = fmt_ctx->streams[stream_index];
  
      /* find decoder for the stream */
  
      dec = avcodec_find_decoder(st->codecpar->codec_id);
  
      if (!dec) {
  
          printf("Failed to find %s codec\n",
  
                  av_get_media_type_string(type));
  
          return AVERROR(EINVAL);
  
      }
  
      /* Allocate a codec context for the decoder */
  
      *dec_ctx = avcodec_alloc_context3(dec);
  
      if (!*dec_ctx) {
  
          printf("Failed to allocate the %s codec context\n",
  
                  av_get_media_type_string(type));
  
          return AVERROR(ENOMEM);
  
      }
  
      /* Copy codec parameters from input stream to output codec context */
  
      if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) &lt; 0) {
  
          printf("Failed to copy %s codec parameters to decoder context\n",
  
                  av_get_media_type_string(type));
  
          return ret;
  
      }
  
      /* Init the decoders, with or without reference counting */
  
      av_dict_set(&amp;opts, "refcounted_frames", refcount ? "1" : "0", 0);
  
      if ((ret = avcodec_open2(*dec_ctx, dec, &amp;opts)) &lt; 0) {
  
          printf("Failed to open %s codec\n",
  
                  av_get_media_type_string(type));
  
          return ret;
  
      }
  
      *stream_idx = stream_index;
  
  }
  
  return 0;
  
  }
  
  
  
  
  
  
  
  int main (int argc, char **argv)
  
  {
  
   int ret = 0, got_frame;
  
  src_filename = argv[1];
  
  video_dst_filename = argv[2];
  
  audio_dst_filename = argv[3];
  
  av_register_all();
  
  avcodec_register_all();
  
  printf("Registered all\n");
  
  
  
  /* open input file, and allocate format context */
  
  if (avformat_open_input(&amp;fmt_ctx, src_filename, NULL, NULL) &lt; 0) {
  
      printf("Could not open source file %s\n", src_filename);
  
      exit(1);
  
  }
  
  
  
  /* retrieve stream information */
  
  if (avformat_find_stream_info(fmt_ctx, NULL) &lt; 0) {
  
      printf("Could not find stream information\n");
  
      exit(1);
  
  }
  
  
  
  if (open_codec_context(&amp;video_stream_idx, &amp;video_dec_ctx, fmt_ctx, 
  
  AVMEDIA_TYPE_VIDEO) >= 0) {
  
      video_stream = fmt_ctx->streams[video_stream_idx];
  
      avformat_alloc_output_context2(&amp;outAVFormatContext, NULL, NULL, 
  
  video_dst_filename);
  
      if (!outAVFormatContext)
  
      {
  
              printf("\n\nError : avformat_alloc_output_context2()");
  
              return -1;
  
      }
  
  }
  
  
  
  if (open_codec_context(&amp;audio_stream_idx, &amp;audio_dec_ctx, fmt_ctx, 
  
  AVMEDIA_TYPE_AUDIO) >= 0) {
  
      audio_stream = fmt_ctx->streams[audio_stream_idx];
  
      audio_dst_file = fopen(audio_dst_filename, "wb");
  
      if (!audio_dst_file) {
  
          printf("Could not open destination file %s\n", audio_dst_filename);
  
          ret = 1;
  
          goto end;
  
      }
  
  }
  
  /* dump input information to stderr */
  
  av_dump_format(fmt_ctx, 0, src_filename, 0);
  
  
  
  if (!audio_stream &amp;&amp; !video_stream) {
  
      printf("Could not find audio or video stream in the input, aborting\n");
  
      ret = 1;
  
      goto end;
  
  }
  
  
  
      output_format = av_guess_format(NULL, video_dst_filename, NULL);
  
      if( !output_format )
  
      {
  
       printf("\n\nError : av_guess_format()");
  
       return -1;
  
      }
  
  
  
      video_st = avformat_new_stream(outAVFormatContext ,NULL);
  
      if( !video_st )
  
      {
  
              printf("\n\nError : avformat_new_stream()");
  
        return -1;
  
      }
  
  
  
      outAVCodecContext = avcodec_alloc_context3(outAVCodec);
  
      if( !outAVCodecContext )
  
      {
  
        printf("\n\nError : avcodec_alloc_context3()");
  
        return -1;
  
      }
  
  
  
  
  
      outAVCodecContext = video_st->codec;
  
      outAVCodecContext->codec_id = AV_CODEC_ID_MPEG4;// AV_CODEC_ID_MPEG4; // 
  
   AV_CODEC_ID_H264 // AV_CODEC_ID_MPEG1VIDEO
  
      outAVCodecContext->codec_type = AVMEDIA_TYPE_VIDEO;
  
      outAVCodecContext->pix_fmt  = AV_PIX_FMT_YUV420P;
  
      outAVCodecContext->bit_rate = 400000; // 2500000
  
      outAVCodecContext->width = 1920;
  
      //outAVCodecContext->width = 500;
  
      outAVCodecContext->height = 1080;
  
      //outAVCodecContext->height = 500;
  
      outAVCodecContext->gop_size = 3;
  
      outAVCodecContext->max_b_frames = 2;
  
      outAVCodecContext->time_base.num = 1;
  
      outAVCodecContext->time_base.den = 30; // 15fps
  
  
  
      if (outAVCodecContext->codec_id == AV_CODEC_ID_H264)
  
      {
  
       av_opt_set(outAVCodecContext->priv_data, "preset", "slow", 0);
  
      }
  
  
  
      outAVCodec = avcodec_find_encoder(AV_CODEC_ID_MPEG4);
  
      if( !outAVCodec )
  
      {
  
       printf("\n\nError : avcodec_find_encoder()");
  
       return -1;
  
      }
  
  
  
      /* Some container formats (like MP4) require global headers to be 
  
   present
  
         Mark the encoder so that it behaves accordingly. */
  
  
  
      if ( outAVFormatContext->oformat->flags &amp; AVFMT_GLOBALHEADER)
  
      {
  
              outAVCodecContext->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
      }
  
  
  
      value = avcodec_open2(outAVCodecContext, outAVCodec, NULL);
  
      if( value &lt; 0)
  
      {
  
              printf("\n\nError : avcodec_open2()");
  
              return -1;
  
      }
  
  
  
  /* create empty video file */
  
      if ( !(outAVFormatContext->flags &amp; AVFMT_NOFILE) )
  
      {
  
       if( avio_open2(&amp;outAVFormatContext->pb , video_dst_filename, 
  
  AVIO_FLAG_WRITE ,NULL, NULL) &lt; 0 )
  
       {
  
        printf("\n\nError : avio_open2()");
  
       }
  
      }
  
  
  
      if(!outAVFormatContext->nb_streams)
  
      {
  
              printf("\n\nError : Output file dose not contain any stream");
  
        return -1;
  
      }
  
  
  
      /* imp: mp4 container or some advanced container file required header 
  
   information*/
  
      value = avformat_write_header(outAVFormatContext , NULL);
  
      if(value &lt; 0)
  
      {
  
              printf("\n\nError : avformat_write_header()");
  
              return -1;
  
      }
  
  
  
      printf("\n\nOutput file information :\n\n");
  
      av_dump_format(outAVFormatContext , 0 ,video_dst_filename ,1);
  
  
  
  
  
      int flag;
  
      int frameFinished;
  
  
  
  
  
      value = 0;
  
  
  
      pAVPacket = (AVPacket *)av_malloc(sizeof(AVPacket));
  
      av_init_packet(pAVPacket);
  
  
  
      pAVFrame = av_frame_alloc();
  
      if( !pAVFrame )
  
      {
  
       printf("\n\nError : av_frame_alloc()");
  
       return -1;
  
      }
  
  
  
      outFrame = av_frame_alloc();//Allocate an AVFrame and set its fields to 
  
   default values.
  
      if( !outFrame )
  
      {
  
       printf("\n\nError : av_frame_alloc()");
  
       return -1;
  
      }
  
  
  
      nbytes = av_image_get_buffer_size(outAVCodecContext-
  
   >pix_fmt,outAVCodecContext->width,outAVCodecContext->height,32);
  
      video_outbuf = (uint8_t*)av_malloc(nbytes);
  
      if( video_outbuf == NULL )
  
      {
  
      printf("\n\nError : av_malloc()");
  
      }
  
  
  
  
  
      value = av_image_fill_arrays( outFrame->data, outFrame->linesize, 
  
   video_outbuf , AV_PIX_FMT_YUV420P, outAVCodecContext-
  
   >width,outAVCodecContext->height,1 ); // returns : the size in bytes 
  
   required for src
  
      if(value &lt; 0)
  
      {
  
      printf("\n\nError : av_image_fill_arrays()");
  
      }
  
  
  
      SwsContext* swsCtx_ ;
  
  
  
      // Allocate and return swsContext.
  
      // a pointer to an allocated context, or NULL in case of error
  
      // Deprecated : Use sws_getCachedContext() instead.
  
      swsCtx_ = sws_getContext(video_dec_ctx->width,
  
                              video_dec_ctx->height,
  
                              video_dec_ctx->pix_fmt,
  
                              video_dec_ctx->width,
  
                              video_dec_ctx->height,
  
                              video_dec_ctx->pix_fmt,
  
                              SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  
  
      AVPacket outPacket;
  
  
  
      int got_picture;
  
  
  
      while( av_read_frame( fmt_ctx , pAVPacket ) >= 0 )
  
      {
  
              if(pAVPacket->stream_index == video_stream_idx)
  
              {
  
                      value = avcodec_decode_video2(video_dec_ctx , pAVFrame , 
  
    &amp;frameFinished , pAVPacket );
  
                      if( value &lt; 0)
  
                      {
  
                              printf("Error : avcodec_decode_video2()");
  
                      }
  
  
  
                      if(frameFinished)// Frame successfully decoded :)
  
                      {
  
                              sws_scale(swsCtx_, pAVFrame->data, pAVFrame-
  
   >linesize,0, video_dec_ctx->height, outFrame->data,outFrame->linesize);
  
  //                              sws_scale(swsCtx_, pAVFrame->data, pAVFrame-
  
  >linesize,0, video_dec_ctx->height, outFrame->data,outFrame->linesize);
  
                              av_init_packet(&amp;outPacket);
  
                              outPacket.data = NULL;    // packet data will be 
  
   allocated by the encoder
  
                              outPacket.size = 0;
  
  
  
                              avcodec_encode_video2(outAVCodecContext , 
  
   &amp;outPacket ,outFrame , &amp;got_picture);
  
  
  
                              if(got_picture)
  
                              {
  
                                      if(outPacket.pts != AV_NOPTS_VALUE)
  
                                              outPacket.pts = 
  
   av_rescale_q(outPacket.pts, video_st->codec->time_base, video_st-
  
   >time_base);
  
                                      if(outPacket.dts != AV_NOPTS_VALUE)
  
                                              outPacket.dts = 
  
   av_rescale_q(outPacket.dts, video_st->codec->time_base, video_st-
  
   >time_base);
  
  
  
                                      printf("Write frame %3d (size= %2d)\n", 
  
   j++, outPacket.size/1000);
  
                                      if(av_write_frame(outAVFormatContext , 
  
   &amp;outPacket) != 0)
  
                                      {
  
                                              printf("\n\nError : 
  
   av_write_frame()");
  
                                      }
  
  
  
                              av_packet_unref(&amp;outPacket);
  
                              } // got_picture
  
  
  
                      av_packet_unref(&amp;outPacket);
  
                      } // frameFinished
  
  
  
              }
  
      }// End of while-loop
  
  
  
      value = av_write_trailer(outAVFormatContext);
  
      if( value &lt; 0)
  
      {
  
              printf("\n\nError : av_write_trailer()");
  
      }
  
  
  
  
  
      //THIS WAS ADDED LATER
  
      av_free(video_outbuf);
  
  
  
  end:
  
      avcodec_free_context(&amp;video_dec_ctx);
  
      avcodec_free_context(&amp;audio_dec_ctx);
  
      avformat_close_input(&amp;fmt_ctx);
  
      if (video_dst_file)
  
          fclose(video_dst_file);
  
     if (audio_dst_file)
  
         fclose(audio_dst_file);
  
     //av_frame_free(&amp;frame);
  
     av_free(video_dst_data[0]);
  
     return ret &lt; 0;
  
  }

  Problem with above code is that it rotates a video to left by 90 degree.

  Snapshot of video given as input to above program

  Snapshot of output video. It is rotated by 90 degree to left.

  I compiled program using below command :

  g++ -D__STDC_CONSTANT_MACROS -Wall -g ScreenRecorder.cpp -I/home/harry/Documents/compressor/ffmpeg-3.3/ -I/root/android-ndk-r14b/platforms/android-21/arch-x86_64/usr/include/ -c -o ScreenRecorder.o -w

  And linked it using below command :

  g++ -Wall -g ScreenRecorder.o -I/home/harry/Documents/compressor/ffmpeg-3.3/ -I/root/android-ndk-r14b/platforms/android-21/arch-x86_64/usr/include/ -L/usr/lib64 -L/lib64 -L/usr/lib/gcc/x86_64-redhat-linux/4.4.7/ -L/home/harry/Documents/compressor/ffmpeg-3.3/ffmpeg-build -L/root/android-ndk-r14b/platforms/android-21/arch-x86_64/usr/lib64 -o ScreenRecorder.exe -lavformat -lavcodec -lavutil -lavdevice -lavfilter -lswscale -lx264 -lswresample -lm -lpthread -ldl -lstdc++ -lc -lrt

  Program is being run using below command :

  ./ScreenRecorder.exe vertical.MOV videoH.mp4 audioH.mp3

  Note :
  - Source video is taken from iphone and is of .mov format.
  - Output video is being stored in .mp4 file.

  Can anyone please tell me why it is rotating video by 90 degree ?

  One thing i noticed in dump is shown below :

    Duration: 00:00:06.04, start: 0.000000, bitrate: 17087 kb/s
  
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 17014 kb/s, 29.98 fps, 29.97 tbr, 600 tbn, 1200 tbc (default)
  
  Metadata:
  
    rotate          : 90
  
    creation_time   : 2017-07-09T10:56:42.000000Z
  
    handler_name    : Core Media Data Handler
  
    encoder         : H.264
  
  Side data:
  
    displaymatrix: rotation of -90.00 degrees

  it says displaymatrix: rotation of -90.00 degrees. Is it responsible for rotating video by 90 degree ?