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• Configuring install path : prefix=[PREFIX] not fully understood

  3 mai 2016, par whatshisface

  I think this is simply a general c++ question :

  I’m attempting to compile a local version of ffmpeg on Linux Fedora using the gnu c++ compiler. I have source code in a bunch of folders under :

  ~/<username>/Downloads/Code/ffmpeg_sources/
  
  </username>

  which is where I’m attempting to set the config flags to install the build to a target not under this tree but at a root level directory with local shared libraries :

  /usr/local/

  There is this following section near the beginning of the configuration file :

  Standard options:
  
  
  
   --prefix=PREFIX          install in PREFIX []
  
   --bindir=DIR             install binaries in DIR [PREFIX/bin]
  
   --datadir=DIR            install data files in DIR [PREFIX/share/ffmpeg]
  
   --docdir=DIR             install documentation in DIR [PREFIX/share/doc/ffmpeg]
  
   --libdir=DIR             install libs in DIR [PREFIX/lib]
  
   --shlibdir=DIR           install shared libs in DIR [PREFIX/lib]
  
   --incdir=DIR             install includes in DIR [PREFIX/include]
  
   --mandir=DIR             install man page in DIR [PREFIX/share/man]
  
   --enable-rpath           use rpath to allow installing libraries in paths
  
                            not part of the dynamic linker search path

  I may have completely misunderstood this, but I thought that setting a value like

  --prefix=/usr/local

  or

  --prefix=[/usr/local]

  might work, but it appears not to, as once the ./config, make&&make install is complete, it has done a bunch of stuff but there’s nothing installed at the target. There are a LOT of new executable files built in the source directory, so presumably the build is working but I’m simply specifying the paths incorrectly ? A part of the same problem is that it’s unclear whether, once I’ve set the

  --prefix=[PREFIX]

  correctly, I need to set all of the further

  --datadir, --libdir

  etc. or whether the first —prefix value is enough ?

  What is the above configuration syntax trying to show me ?

• Configuring install path : prefix=[PREFIX] not fully understood

  29 septembre 2019, par whatshisface

  I think this is simply a general c++ question :

  I’m attempting to compile a local version of ffmpeg on Linux Fedora using the gnu c++ compiler. I have source code in a bunch of folders under :

  ~/<username>/Downloads/Code/ffmpeg_sources/
  
  </username>

  which is where I’m attempting to set the config flags to install the build to a target not under this tree but at a root level directory with local shared libraries :

  /usr/local/

  There is this following section near the beginning of the configuration file :

  Standard options:
  
  
  
   --prefix=PREFIX          install in PREFIX []
  
   --bindir=DIR             install binaries in DIR [PREFIX/bin]
  
   --datadir=DIR            install data files in DIR [PREFIX/share/ffmpeg]
  
   --docdir=DIR             install documentation in DIR [PREFIX/share/doc/ffmpeg]
  
   --libdir=DIR             install libs in DIR [PREFIX/lib]
  
   --shlibdir=DIR           install shared libs in DIR [PREFIX/lib]
  
   --incdir=DIR             install includes in DIR [PREFIX/include]
  
   --mandir=DIR             install man page in DIR [PREFIX/share/man]
  
   --enable-rpath           use rpath to allow installing libraries in paths
  
                            not part of the dynamic linker search path

  I may have completely misunderstood this, but I thought that setting a value like

  --prefix=/usr/local

  or

  --prefix=[/usr/local]

  might work, but it appears not to, as once the ./config, make&&make install is complete, it has done a bunch of stuff but there’s nothing installed at the target. There are a LOT of new executable files built in the source directory, so presumably the build is working but I’m simply specifying the paths incorrectly ? A part of the same problem is that it’s unclear whether, once I’ve set the

  --prefix=[PREFIX]

  correctly, I need to set all of the further

  --datadir, --libdir

  etc. or whether the first —prefix value is enough ?

  What is the above configuration syntax trying to show me ?

• Is there any control property to fix video playback speed problem when using ffmpeg to decode in Qt platform ?

  16 février 2019, par SoloWang

  I want to play local video file in Qt platform using ffmpeg to decode.Everything is OK except that play speed is as twice as normal.
  The first thing I think about is that there must be a sampling frequency involved.But to be a new to ffmpeg,I don’t know how to fix this problem.
  Above is my code to read frame,is anyone can tell me what’s wrong with the code ?

  void VideoThread::run()
  
  {
  
      m_pInFmtCtx = avformat_alloc_context(); //ini struct
  
      char path[] = "d:/test.mp4";
  
      // open specific file
  
      if(avformat_open_input(&m_pInFmtCtx, *path, NULL, NULL)){ 
  
      {
  
          qDebug()<<"get rtsp failed";
  
          return;
  
      }
  
      else
  
      {
  
          qDebug()<<"get rtsp success";
  
      }
  
  
  
  
  
      if(avformat_find_stream_info(m_pInFmtCtx, NULL) < 0)
  
      {
  
          qDebug()<<"could not find stream information";
  
          return;
  
      }
  
      int nVideoIndex = -1;
  
      for(int i = 0; i < m_pInFmtCtx->nb_streams; i++)
  
      {
  
          if(m_pInFmtCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
  
          {
  
              nVideoIndex = i;
  
              break;
  
          }
  
      }
  
      if(nVideoIndex == -1)
  
      {
  
          qDebug()<<"could not find video stream";
  
          return;
  
      }
  
  
  
      qDebug("---------------- File Information ---------------");
  
      m_pCodecCtx = m_pInFmtCtx->streams[nVideoIndex]->codec;
  
      m_pCodec = avcodec_find_decoder(m_pCodecCtx->codec_id);
  
      if(!m_pCodec)
  
      {
  
          qDebug()<<"could not find codec";
  
          return;
  
      }
  
      //start Decoder
  
      if (avcodec_open2(m_pCodecCtx, m_pCodec, NULL) < 0) {
  
          qDebug("Could not open codec.\n");
  
          return;
  
      }
  
  
  
  
  
      //malloc space for stroring frame
  
      m_pFrame     = av_frame_alloc();
  
      m_pFrameRGB  = av_frame_alloc();
  
      m_pOutBuf = (uint8_t*)av_malloc(avpicture_get_size(AV_PIX_FMT_RGB32, m_pCodecCtx->width, m_pCodecCtx->height));
  
      avpicture_fill((AVPicture*)m_pFrameRGB, m_pOutBuf, AV_PIX_FMT_RGB32, m_pCodecCtx->width, m_pCodecCtx->height);
  
  
  
      //for color switch,from YUV to RGB
  
      struct SwsContext *pImgCtx = sws_getContext(m_pCodecCtx->width, m_pCodecCtx->height, m_pCodecCtx->pix_fmt,
  
                                                  m_pCodecCtx->width, m_pCodecCtx->height, AV_PIX_FMT_RGB32, SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  
  
      int nSize = m_pCodecCtx->width * m_pCodecCtx->height;
  
      m_pPacket = (AVPacket *)av_malloc(sizeof(AVPacket));
  
      if(av_new_packet(m_pPacket, nSize) != 0)
  
      {
  
          qDebug()<<"new packet failed";
  
      }
  
  
  
      //isInterruptionRequested is a flag,determine whether the thread is over
  
      // read each frame from specific video file
  
      while (!isInterruptionRequested())
  
      {
  
          int nGotPic = 0;
  
          if(av_read_frame(m_pInFmtCtx, m_pPacket) >= 0)
  
          {
  
              if(m_pPacket->stream_index == nVideoIndex)
  
              {
  
                  //avcodec_decode_video2()transform from packet to frame
  
                  if(avcodec_decode_video2(m_pCodecCtx, m_pFrame, &nGotPic, m_pPacket) < 0)
  
                  {
  
                      qDebug()<<"decode failed";
  
                      return;
  
                  }
  
                  if(nGotPic)
  
                  {   // transform to RGB color
  
                      sws_scale(pImgCtx, (const uint8_t* const*)m_pFrame->data,
  
                                m_pFrame->linesize, 0, m_pCodecCtx->height, m_pFrameRGB->data,
  
                                m_pFrameRGB->linesize);
  
                      // save to QImage,for later use
  
                      QImage *pImage = new QImage((uchar*)m_pOutBuf, m_pCodecCtx->width, m_pCodecCtx->height, QImage::Format_RGB32);
  
                  }
  
  
  
              }
  
          }
  
  
  
          av_free_packet(m_pPacket);
  
          msleep(5);
  
      }
  
      exec();
  
  }