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• FFMPEG : Set Opacity of audio waveform color

  13 août 2018, par Software Development Consultan

  I was trying to do transparency in waveform generated. It seems there is not direct option in ’showwaves’ filter so I came across ’colorkey’ which might help.

  I am trying with following :

  ffmpeg -y -loop 1 -threads 0 -i background.png -i input.mp3 -filter_complex "[1:a]aformat=channel_layouts=mono,showwaves=s=1280x100:rate=7:mode=cline:scale=sqrt:colors=0x0000ff,colorkey=color=0x0000ff:similarity=0.01:blend=0.1[v] ; [0:v][v] overlay=0:155 [v1]" -map "[v1]" -map 1:a -c:v libx264 -crf 35 -ss 0 -t 5 -c:a copy -shortest -pix_fmt yuv420p -threads 0 test_org.mp4

  So I wanted to blue color waveform and wanted to set opacity of that 1 to 0 let say. But it seems this generates blackbox which is actual background of ’1280x100’. I want to keep background of waveform transparent and just wanted to change opacity of waveform only.

  Result of my command : enter image description here

  

  Can you please let me know your suggestion

  @Gyan, this is with reference to following question which you have answered.

  Related last question

  Thanks, Hardik

• Broken output from libavcodec/swscale, depending on resolution

  3 juin 2014, par dtumaykin

  I am writing a video conference software, I have a H.264 stream decoded with libavcoded into IYUV and than rendered into a window with VMR9 in windowless mode. I use a DirectShow graph to do so.

  To avoid unnecessary conversion into RGB and back (see link), I convert IYUV video into YUY2 before passing it to VMR9, with libswscale.

  I noticed that with video resolution of 848x480, output video is broken, so I investigated further and came up that for some resolutions video is always broken. To exclude the libswscale from elaboration, I added support for IYUV+padding to IYUV conversion, and it worked, with all resolutions.

  Still, I was willing to avoid slow IYUV, so I implemented support for NV12 (with libswscale) and YV12 (manually, essentially the same as IYUV). After doing some tests on two different computers, I came up with strange results.

  resolution  YUY2    NV12    IYUV    YV12
  
  PC 1 (my laptop)                
  
  640x360     ok      broken  ok      broken
  
  848x480     broken  broken  ok      broken
  
  960x540     broken  broken  ok      broken
  
  1024x576    ok      ok      ok      ok
  
  1280x720    ok      ok      ok      broken
  
  1920x1080   ok      broken  ok      broken
  
  
  
  PC 2                
  
  640x360     ok      ok      ok      ok
  
  848x480     ok      broken  ok      broken
  
  960x540     ok      ok      ok      ok
  
  1024x576    ok      ok      ok      ok
  
  1280x720    ok      broken  ok      ok
  
  1920x1080   ok      ok      ok      ok

  To exclude VMR9 fault, I substituted it with EVR, but with same results.

  I know that padding is needed for memory alignment, and that the size of padding depends on CPU used (libavcodec doc), that may explain difference between two computers(first has Intel i7-3820QM, the second Intel Core 2 Quad Q6600). I suppose it has something to do with padding, because images are corrupted in certain way.
  
  You can see my blue t-shirt in lower part of image, and my face in the upper one.

  To follow is the code for the conversion. NV12 and YUY2 conversions are performed with libswscale, while IYUV and YV12 manually.

  int pixels = _outputFrame->width * _outputFrame->height;
  
  if (_outputFormat == "YUY2") {
  
      int stride = _outputFrame->width * 2;
  
      sws_scale(_convertCtx, _outputFrame->data, _outputFrame->linesize, 0, _outputFrame->height, &out, &stride);
  
  }
  
  else if (_outputFormat == "NV12") {
  
      int stride[] = { _outputFrame->width, _outputFrame->width };
  
      uint8_t * dst[] = { out, out + pixels };
  
      sws_scale(_convertCtx, _outputFrame->data, _outputFrame->linesize, 0, _outputFrame->height, dst, stride);
  
  }
  
  else if (_outputFormat == "IYUV") { // clean ffmpeg padding
  
      for (int i = 0; i < _outputFrame->height; i++) // copy Y
  
          memcpy(out + i * _outputFrame->width, _outputFrame->data[0] + i * _outputFrame->linesize[0] , _outputFrame->width);
  
      for (int i = 0; i < _outputFrame->height / 2; i++) // copy U
  
          memcpy(out + pixels + i * _outputFrame->width / 2, _outputFrame->data[1] + i * _outputFrame->linesize[1] , _outputFrame->width / 2);            
  
      for (int i = 0; i < _outputFrame->height / 2; i++) // copy V
  
          memcpy(out + pixels + pixels/4 + i * _outputFrame->width / 2, _outputFrame->data[2] + i * _outputFrame->linesize[2] , _outputFrame->width / 2);
  
  } 
  
  else if (_outputFormat == "YV12") { // like IYUV, but U is inverted with V plane
  
      for (int i = 0; i < _outputFrame->height; i++) // copy Y
  
          memcpy(out + i * _outputFrame->width, _outputFrame->data[0] + i * _outputFrame->linesize[0], _outputFrame->width);
  
      for (int i = 0; i < _outputFrame->height / 2; i++) // copy V
  
          memcpy(out + pixels + i * _outputFrame->width / 2, _outputFrame->data[2] + i * _outputFrame->linesize[2], _outputFrame->width / 2);
  
      for (int i = 0; i < _outputFrame->height / 2; i++) // copy U
  
          memcpy(out + pixels + pixels / 4 + i * _outputFrame->width / 2, _outputFrame->data[1] + i * _outputFrame->linesize[1], _outputFrame->width / 2);
  
  }

  out is an output buffer. _outputFrame is libavcodec output AVFrame. _convertCtx is initialized as follows.

  if (_outputFormat == "YUY2")
  
      _convertCtx = sws_getContext(_width, _height, AV_PIX_FMT_YUV420P,
  
                                   _width, _height, AV_PIX_FMT_YUYV422, SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);
  
  else if (_outputFormat == "NV12")
  
      _convertCtx = sws_getContext(_width, _height, AV_PIX_FMT_YUV420P,
  
                                   _width, _height, AV_PIX_FMT_NV12, SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);

  Questions :

  1. Are manual conversions correct ?
  2. Are my assumptions correct ?
  3. Is previous two answers are positive, where is the problem ? And especially...
  4. Why it presents only with some resolutions and not others ?
  5. What additional info can I provide ?

• Gradient is bad in video [closed]

  1er juillet 2023, par Andres Miguel Campos

  I'm trying to capture a css animation with gradient. But when capturing the video I get a bad quality

  


  I have used the following css for the screen

  


  


  


  &#xA;&#xA;&#xA;&#xA;  &#xA;  &#xA;&#xA;&#xA;&#xA;&#xA;  <div class="horizontal-gradient">&#xA;&#xA;  </div>&#xA;&#xA;&#xA;&#xA;

  


  


  



  I have also used the following libraries or frameworks

  


  


  puppeteer-screen-recorder(NodeJS)

  


  


  


  Canvas(JavaScript)

  


  


  


  remotion.dev(Reac and Nodejs)

  


  


  


  Obs

  


  


  But it still shows me poor video quality

  


  

  


  Any support is welcome