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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 :)

• 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

  


• How to use rotate filter in FFmpeg ? [duplicate]

  14 décembre 2020, par shubham rawat

  I have to overlay text at each second of the video and the text should be tilt. I am able to overlay text but can't rotate the text. The command I am using to overlay is.

  


  ffmpeg -y -i gta5.mp4 -vf "[in]drawtext=text=\'"ALT"\': fontcolor=white: borderw=2: fontfile=Arial #Black:fontsize=w*0.04: x=(w-text_w)/1.5: y=120: enable=\'between(t,0,'+str(last_point)+')\',drawtext=text=\'"0"\': fontcolor=blue: borderw=2: fontfile=Arial #Black:fontsize=w*0.04: x=(w-text_w)/1.5: y=70: enable=\'between(t,0.00,10)\'[out]" -codec:a copy mos.mp4


  


  I want to use the rotate filter in this command or any filter which can tilt the text by some degrees.
I know how to rotate one text as it is already answered in Overlaying text on video with required angle using FFMPEG but I am having issues with multiple texts at different times.