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• Does this code contain a potential memory leak ?

  26 juillet 2017, par Johnnylin

  Here is the code :

  cv::Mat YV12ToBRG24_FFmpeg(unsigned char* pYUV, int width,int height)
  
  {
  
      if (width < 1 || height < 1 || pYUV == nullptr){
  
          return cv::Mat();
  
      }
  
  
  
      cv::Mat result(height,width,CV_8UC3, cv::Scalar::all(0));
  
      uchar* pBGR24 = result.data;
  
  
  
      AVFrame* pFrameYUV = av_frame_alloc();
  
      pFrameYUV->width = width;
  
      pFrameYUV->height = height;
  
      pFrameYUV->format = AV_PIX_FMT_YUV420P;
  
      av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, pYUV, AV_PIX_FMT_YUV420P, width, height, 1);
  
  
  
      //U,V exchange
  
      uint8_t * ptmp=pFrameYUV->data[1];
  
      pFrameYUV->data[1]=pFrameYUV->data[2];
  
      pFrameYUV->data[2]=ptmp;
  
  
  
      AVFrame* pFrameBGR = av_frame_alloc();
  
      pFrameBGR->width = width;
  
      pFrameBGR->height = height;
  
      pFrameBGR->format = AV_PIX_FMT_BGR24;
  
      av_image_fill_arrays(pFrameBGR->data, pFrameBGR->linesize, pBGR24, AV_PIX_FMT_BGR24, width, height, 1);
  
  
  
      struct SwsContext* imgCtx = nullptr;
  
      imgCtx = sws_getContext(width,height,AV_PIX_FMT_YUV420P,width,height,AV_PIX_FMT_BGR24,SWS_BILINEAR,0,0,0);
  
      if (imgCtx != nullptr){
  
          sws_scale(imgCtx,pFrameYUV->data,pFrameYUV->linesize,0,height,pFrameBGR->data,pFrameBGR->linesize);
  
          sws_freeContext(imgCtx);
  
          imgCtx = nullptr;
  
          ptmp = nullptr;
  
          pBGR24 = nullptr;
  
          av_frame_free(&pFrameYUV);
  
          av_frame_free(&pFrameBGR);
  
          return result;
  
      }
  
      else{
  
          sws_freeContext(imgCtx);
  
          imgCtx = nullptr;
  
          ptmp = nullptr;
  
          pBGR24 = nullptr;
  
          av_frame_free(&pFrameYUV);
  
          av_frame_free(&pFrameBGR);
  
          return cv::Mat();
  
      }
  
  }

  This function is called every 40 ms (25 fps) and I saw a significant memory increase after several days(like 12GB). But if I ran this code for hours, the memory leak problem would not be obvious enough to be observed.

  Can anyone help ?
  Thanks.

• Rotate mp4 videos without re-encoding

  6 juillet 2024, par stedes

  I'm looking for a way to rotate videos shot with my Nexus 4 on my Debian Wheezy sytem. The videos are shot in portrait mode and I would like to rotate them to landscape mode. Preferably the rotation is command-line driven.

  



  I have found several previous questions which are hinting at a good solution but I can't seem to manage to get it working.

  



  To begin with there was this question :
Rotating videos with FFmpeg

  



  But it indicates that ffmpeg is outdated and that I should use avconv. I found this question detailing the way to go forward.
https://askubuntu.com/questions/269429/how-can-i-rotate-video-by-180-degrees-with-avconv

  



  This made me using following command :

  



  avconv -i original.mp4 -vf "transpose=1" -codec:v libx264 -preset slow -crf 25 -codec:a copy flipped.mp4


  



  However, this is painstakingly slow (last test took me more than 6 hours for less than 3 minutes of footage) and does not result in a playable movie. I also get an error in logging output which states Mb Rate > level limit.

  



  Is there an issue here with the re-encoding ? Should I first re-encode the videos from my phone to another, more "workable" encoding before applying the rotations ? Or am I missing another important point ?

  


• How to use Visual Studio Compiled libs with MSYS pkg-config

  18 août 2017, par maxhap

  First a bit of background.

  I’m trying to compile ffmpeg on windows with the libass extensions/configuration option.

  Using the visual studio project libass-msvc I built libass using Visual Studio as a static lib.

  I then installed MinGW with MSYS and pkg-config. Following the instructions on the ffmpeg MSVC installation guide I configured the environment to build with the MSVC linker and to build in x64.

  When I try to configure libass for compilation using ./configure —enable-libass —toolchain=msvc I get the following error in the log file :

  File not found ass/ass.h
  
  pkg-config can not find libass

  I have tried the following to fix this.

  1. Create a .pc file for libass and add this to the PKG_CONFIG_PATH environment variable. See file content below. (After doing this pkg-config libass —version prints 0.81, not the right version number but at least something.)

  2. Copy libass .h files into a MinGW/include/ass folder and the .lib file into the MinGW/libs folder.

  3. Add libass include and bin folders to PATH environment variable

  4. Download libass and dependencies source then try to build it using MSYS with MSVC compiler. My aim here was to be able to use "make install" and let MinGW install libass to the correct locations. After hours of trying to fix linker errors, I abandoned this idea as some of the libass dependencies make files only work with the GCC GNU compiler.

  5. Compile libass with GCC GNU using MinGW make/make install then try and install libass using the GNU libs. Again this led to linker errors (I know this was a bad idea but was worth a try).

  6. Tried using extra lib and include build configuration options —extra-cflags="ffmpeg-dir/extra/include" \
     — extra-ldflags="ffmped-dir/extra/ffmpeg_build/lib" then adding the libs and .h files into those locations

  .pc file

  libass.pc:
  
  prefix=/MinGW
  
  includedir=libass-directory/include
  
  libdir=libass-director/x64/bin/
  
  
  
  Name: libass
  
  Description: Libass project
  
  Version: 0.13.7

  I am now completely stuck and out of ideas if anyone could give any insight or suggestions into what I’m doing wrong that would be fantastic.

  Thanks in advanced !