Sur d’autres sites (12003)

• FFMPEG, Blur an area of a video using Image Select Areas Plugin

  12 juillet 2016, par Drupalist

  I am building an online video editor. I need to allow the users to blur an area of movies. This must be done graphically, I mean user should be able to select an area of a video, using an screenshot, then the selected area must be blurred. Some thing like this

  

  Is there anyway to map this selected area dimension and its distance from borders to the real values that must be applied to the video ?

  I mean four numbers, width, length, top, left will be provided using this plug in and I need to use these numbers to blur an area of videos.

  I take an screenshot of video. In order to keep the aspect ratio, I will fix the width to 800px and let the height to be scaled up/down. It is clear that the width, length, top, left of the selected area of the screenshot is a factor of the width, length, top, left of the area that must be blurred in video. but I don’t know how to get this factor. Besides that I don’t know how to get the video resolution.

  Thanks in advance.

  ---

  Update

  This is my PHP code that gets the selected area dimensions and offsets

  $iLeft = $_POST['left'];
  
  $iTop = $_POST['top'];
  
  $iWidth = $_POST['width'];
  
  $iHeight = $_POST['height'];
  
  exec('ffmpeg -i '.$url.' -filter_complex "[0:v]scale=iw*sar:ih,setsar=1,split[bg][bb];[bb]crop='.$iWidth.'*iw/800:iw*'.$iHeight.'/800:'.$iWidth.'*iw/800:'.$iHeight.'*iw/800,boxblur=10[b0];[bg][b0]overlay='.$iLeft.'*W/800:'.$iTop.'*W/800"" '.$name.' > block.txt 2>&1');

  $iLeft, $iTop, $iWidth, $iHeight are the left, top, width and height of the selected area via the image plugin.

  It blurs many selected areas very well, but areas like this

  

  The Image Left, Top, Width, Height is 257,  39.26666259765625,  10,  391

  don’t get blurred. Also a video with Dimension 207x207 didn’t get blurred as well.

• MP4Box Resolution unmatched between representation

  30 janvier 2018, par Massimo Vantaggio

  for one of the last stability tests i try with two representation instead the only one of before to get the adaptive bitrate streaming .
  Below my encoding command :

  ffmpeg -y -i $name -i logo.png -c:a aac -b:a 256k -ar 48000 -ac 2 -async 1 -c:v libx264 -x264opts keyint=$GOP:min-keyint=$GOP:no-scenecut -bf 0 -r $FPSC -b:v 1060k -maxrate 1060k -bufsize 530k -profile:v main -t $FDUR -filter_complex "[0:v][1:v]overlay=main_w-overlay_w-10:10,scale=-1:478" format480.mp4
  
  
  
  ffmpeg -y -i $name -i logo.png -c:a aac -b:a 384k -ar 48000 -ac 2 -async 1 -c:v libx264 -x264opts keyint=$GOP:min-keyint=$GOP:no-scenecut -bf 0 -r $FPSC -b:v 2400k -maxrate 2400k -bufsize 1200k -profile:v main -t $FDUR -filter_complex "[0:v][1:v]overlay=main_w-overlay_w-10:10,scale=-1:1080" format1080.mp4

  If for the first rapresentation i use 480p ffmpeg give me this error :

  width not divisible by 2 (853x480)
  Error initializing output stream

  If i use for first representation 478p ffmpeg run correctly all two encoding but after when i try to load these two files on MP4Box to dash them live with the following command :

  MP4Box -dash-live 8000 -subdur 8000 -profile dashavc264:live -mpd-refresh 240.0 -time-shift 24 -min-buffer 4000 -insert-utc -no-cache -out manifest.mpd format1080.mp4#video format480.mp4#video format1080.mp4#audio format480.mp4#audio

  the error come back into mp4box :
  "files have not-proportional layout 1920 x 1080 vs 849 x 478 but sample size and aspect ratio match, assuming precision issue"

  I would like to understand what i don’t know about, which are the resolutions that match, i understand that some movies have atypical resolution for example 1040 or 432 but the input video for this test is correct 1920 X 1080 and i wish to compress/encode it for dash and to create another representation with 480p, could i ask where I’m wrong ?
  Thanks !
  Massimo

• ffmpeg Cg shader ITU 709 YCbYg

  22 juillet 2018, par user2517097

  I have a viewer (mrViewer at sourceforge) that displays movie files by feeding YCbCr images and merging them later in a shader. Currently I am trying to track a color issue in my viewer, not displaying DNxHD movies properly. The EXR file is to be seen in RGB, not scene linear. The movie was created from that EXR file in Nuke (a comp program). All movie files are converted from EXR image without color space conversion in NUKE 11. All movie files are encoded with video color range.

  Color_Profile_nuke11.exr

  Color_Profile_nuke11_DNxHD_mov64_444.mov

  Color_Profile_nuke11_DNxHD_mov64_422.mov

  In the shader, I do (simplified Cg code) :

    half3 pre;
  
  
  
    pre.r = tex2D(YImage, tc).r;  // Y
  
    pre.g = tex2D(UImage, tc).r;  // U
  
    pre.b = tex2D(VImage, tc).r;  // V
  
  
  
    half3 c;
  
  
  
    if ( coeffs )
  
    {
  
        pre += Koff;
  
  
  
        c.r = dot(Kr, pre);
  
        c.g = dot(Kg, pre);
  
        c.b = dot(Kb, pre);
  
    }
  
    else
  
    {
  
  
  
        half3 yuv;
  
  
  
        yuv.r = 1.1643 * ( pre.r - 0.0625 );
  
        yuv.g = pre.g - 0.5;
  
        yuv.b = pre.b - 0.5;
  
  
  
        c.r = yuv.r + 1.5958 * yuv.b;
  
        c.g = yuv.r - 0.39173 * yuv.g - 0.81290 * yuv.b;
  
        c.b = yuv.r + 2.017 * yuv.g;
  
    }
  
  
  
    Out output;
  
    output.pixel = c;
  
    return output;
  
  
  
  
  
  
  
  // Send coeffs to shader shader (C++ code)
  
  {
  
  _shader->setUniform( "coeffs", 1 );
  
  // HDTV  YCbCr coefficients
  
  _shader->setUniform( "Koff", 0.0f, -0.5f, -0.5f );
  
  _shader->setUniform( "Kr", 1.0f, 0.0f, 1.28033f );
  
  _shader->setUniform( "Kg", 1.0f, -0.21482f, -0.38059f );
  
  _shader->setUniform( "Kb", 1.0f, 2.12798f, 0.0f );
  
  }

  Now, my problem is that the ITU 709 (the one with the dot() calls) path seems to not be behaving properly. It creates a washed out image. I am wondering if this has to do with full jpeg and full mpeg not having taken into account or whether my coefficients are wrong.

  If I set the color matrix to ITU709 in my C++ code with the ffmpeg library and let its swscale do the conversion, I get good color correspondence in the image if I select the (default) 601 path in the shader.