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• Best / simplest way to display FFmpeg frames in Qt5

  7 mars 2018, par esterlein

  I need to display ffmpeg frames on Qt widget. I know about QtFFmpegWrapper, but it seems outdated. I tried to use memcpy() to copy data from RGB ffmpeg frame to QImage and got unhandled exception inside it.

  QImage lastFrame;
  
  lastFrame = QImage( screen_w, screen_h, QImage::Format_RGB888 );
  
  for( int y = 0; y < screen_h; ++y )
  
      memcpy( lastFrame.scanLine(y),
  
              frameRGB -> data[0] + y * frameRGB -> linesize[0],
  
              screen_w * 3 );

  I tried sws_getContext() and sws_getCachedContext(), AV_PIX_FMT_BGR24 and AV_PIX_FMT_RGB24 in all parts of ffmpeg processing. All ffmpeg code is from popular tutorials and works fine with SDL and PIX_FMT_YUV420P.

  Any ideas ?
  Maybe it’s not the best/simplest way to display ffmpeg frames on Qt widget ?

  Edit.

  Ok, I used Murat Şeker’s solution with QImage::copy() but now QImage::isNull() returns true.

  Some of my ffmpeg code :

  out_buffer = (uint8_t*)av_malloc( avpicture_get_size( AV_PIX_FMT_RGB32, 
  
                                    codecCtx -> width, codecCtx -> height ));
  
  avpicture_fill((AVPicture *)frameRGB, out_buffer, AV_PIX_FMT_RGB32,
  
                 codecCtx -> width, codecCtx -> height);
  
  img_convert_ctx = sws_getContext( codecCtx -> width, codecCtx -> height, 
  
                                    codecCtx -> pix_fmt, codecCtx -> width, 
  
                                    codecCtx -> height, AV_PIX_FMT_RGB32, 
  
                                    SWS_BICUBIC, NULL, NULL, NULL );
  
  /* ... */
  
  
  
  if( got_picture ){
  
      sws_scale( img_convert_ctx, (const uint8_t* const*)frame -> data,
  
                 frame -> linesize, 0, codecCtx -> height, frameRGB -> data,
  
                 frameRGB -> linesize );
  
      QImage imgFrame = QImage( frameRGB -> data[0], frameRGB -> width,
  
                                frameRGB -> height, frameRGB -> linesize[0],
  
                                QImage::Format_RGB32 ).copy();
  
      if( imgFrame.isNull()){} // true
  
  
  
      // But I can write this frame to hard disk using BITMAPFILEHEADER
  
      SaveBMP( frameRGB, codecCtx -> width, codecCtx -> height ); // it works
  
  }

• ffmpeg_opt : fix max_error_rate help info display issue.

  23 février 2018, par Jun Zhao

  ffmpeg_opt : fix max_error_rate help info display issue.
  ffmpeg -h display "max_error_rate" option help information have
  
  been cut off, the root cause is used a wrong initial order.
  Signed-off-by : Jun Zhao <jun.zhao@intel.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] fftools/ffmpeg_opt.c

• ffplay - Two videos (.mp4), one display screen and just a few seconds to display them together [closed]

  1er juillet 2024, par Gabe Mata

  I have two videos (.mp4), one display screen and just a few seconds to display them together.

  


  I am able to displayed them together on a split screen via ffmpeg and then opening the output file. The problem is that it takes a long time (3 minutes).

  


  Here is the Code : (first code)

  


  ffmpeg -i _20180114094126_flightvideo_cam1.mp4      \
       -i _20180114094126_flightvideo_cam2.mp4       \
       -filter_complex "                              \
               [0:v]crop=1280:360:0:0[v0];             \
               [1:v]scale=1280:-1,crop=1280:360:0:0[v1];\
               [v0] [v1]vstack[v]" \
       -map [v]                     \
       -vcodec libx264               \
       -pix_fmt yuv420p               \
       -preset ultrafast               \
        6000screen_take1.mkv  


  


  On the other hand, when using ffplay I am able to modify one video at the time and play it right away :

  


  $ ffplay -i _20180114094126_flightvideo_cam1.mp4 -vf scale=425:-2 


  


  How can I have the same outcome as the first code above, but display it on my screen right away(without waiting for the output file to be created, 3 minutes in this case) ?

  


  Please let me know if this is not clear.