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• Wrong colors when converting an AVFrame to QVideoFrame

  2 janvier 2020, par Michael G.

  I read videos with libav and display them in a QAbstractVideoSurface in QML. It works so far, however, I did not manage to get the colors right.

  My av_read_frame Loop looks like this :

  if (frameFinished)
  
  {
  
                          SwsContext* context = nullptr;
  
                          context = sws_getContext(_frame->width, _frame->height, (AVPixelFormat)_frame->format, _frame->width, _frame->height, AVPixelFormat::AV_PIX_FMT_RGBA, SWS_BICUBIC, nullptr, nullptr, nullptr);
  
                          QImage img(_frame->width, _frame->height, QImage::Format_RGBA8888);
  
                          uint8_t* dstSlice[] = { img.bits() };
  
                          int dstStride = img.width() * 4;
  
                          sws_scale(context, _frame->data, _frame->linesize,
  
                              0, _frame->height, dstSlice, &dstStride);
  
  
  
                          av_packet_unref(&packet);
  
                          sws_freeContext(context);
  
  }

  If I save the image to disk at this point, the colors are already wrong (everything looks red).
  Later, I display the images in a video surface with the format QVideoFrame::Format_ARGB32, and the colors are wrong again, but look different than the saved image (everything looks blue).

  I started to experiment with libav/ffmpeg recently, so maybe the problem is something else and I just have no clue. Let me know, if you need more information :)

• vqf : Make sure sample_rate is set to a valid value

  27 septembre 2013, par Martin Storsjö

  vqf : Make sure sample_rate is set to a valid value
  This avoids divisions by zero later (and possibly assertions in
  
  time base scaling), since an invalid rate_flag combined with an
  
  invalid bitrate below could pass the mode combination test.
  Reported-by : Mateusz "j00ru" Jurczyk and Gynvael Coldwind
  
  CC : libav-stable@libav.org
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/vqf.c

• FFmpeg Drawbox Errors ?

  12 mars 2021, par Alex Gurr

  Using ffmpeg version 4.3.2.

  


  Command :

  


  ffmpeg -y

  -i /usr/src/app/backgrounds/pink-blue.jpg
  -i files/fuzzy-octopus-5/path/file.webm
  -i files/fuzzy-octopus-5/path/file.webm
  -i /usr/src/app/logo.png
  -filter_complex "
    [0]drawbox=x=-140:y=(((H-th)/2) - 205):w=840:h=490:color=white@0.2:t=fill,
       drawbox=x=770:y=(((H-th)/2) - 205):w=840:h=490:color=white@0.2:t=fill[bg]; 
    ...


  


  However I am getting the following errors ?

  


  Error while processing the decoded data for stream #3:0
Failed to inject frame into filter network: Invalid argument
Error reinitializing filters!
[Parsed_drawbox_0 @ 0x564a87058e80] Failed to configure input pad on Parsed_drawbox_0
[Parsed_drawbox_0 @ 0x564a87058e80] Error when evaluating the expression '(((H-th)/2) - 205)'.
Last message repeated 5 times
[Parsed_drawbox_0 @ 0x564a87058e80] [Eval @ 0x7ffcf25dc650] Undefined constant or missing '(' in 'H-th)/2)-205)'


  


  I have the right amount of brackets and this definitely works on my local machine (macOS). It's only throwing this error in our deployed AWS EC2 linux instance.

  


  Any ideas ? Thanks !

  


  Update : Tried replacing th with h but get the same error