Recherche avancée

Sur d’autres sites (5066)

• 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.

• ffmpeg merge video and audio + fade out

  1er mai 2016, par jacky brown

  I have one video file and one audio file.
  I want to merge them together that the final output video will be in the length of the video and will contain the audio in the background.

  i did :

  ffmpeg -i output.avi -i bgmusic.mp3 -filter_complex " [1:0] apad " -shortest out.avi

  but the background audio is cut in the end of the final merge movie.
  i want it to fade out nicely.

  how can i do it ??

  but the background audio is cut in the end of the final merge movie.
  i want it to fade out nicely.

  how can i do it ??

  thanks.

• ffmpeg & png watermark issue

  2 décembre 2013, par mindcast

  I tried to create a watermark (using a png image) on a video like this :

  ffmpeg -i test.wmv -b:a 300k -ar 22050 -t 10 -f flv -s 352x288 -vf "movie = watermark_logo352.png [watermark]; [in][watermark] overlay =0:0 [out]" out.flv

  but I get the error :

  ffmpeg version 0.10.4 Copyright (c) 2000-2012 the FFmpeg developers
  
  built on Jun 14 2012 13:14:31 with gcc 4.4.5   configuration:
  
  --prefix=/home/username --enable-cross-compile --enable-shared --arch=amd64 --target-os=linux --disable-yasm --enable-decoder=png --enable-encoder=png   
  
          libavutil      51. 35.100 / 51. 35.100   
  
          libavcodec     53. 61.100 / 53. 61.100   
  
          libavformat    53. 32.100 / 53. 32.100   
  
          libavdevice    53.  4.100 / 53.  4.100   
  
          libavfilter     2. 61.100 /  2. 61.100   
  
          libswscale      2.  1.100 /  2.  1.100   
  
          libswresample   0.  6.100 /  0.  6.100 
  
          Input #0, asf, from 'test.wmv':   
  
          Metadata:
  
              >     WMFSDKVersion   : 9.00.00.2980
  
              >     WMFSDKNeeded    : 0.0.0.0000
  
              >     IsVBR           : 1
  
              >     VBR Peak        : 351
  
              >     Buffer Average  : 728   Duration: 00:00:05.59, start: 0.000000, bitrate: 574 kb/s
  
              >     Stream #0:0(jpn): Audio: wmav2 (a[1][0][0] / 0x0161), 22050 Hz, 2 channels, s16, 32 kb/s
  
              >     Stream #0:1(jpn): Video: wmv1 (WMV1 / 0x31564D57), yuv420p, 352x288, 520 kb/s, SAR 8:9 DAR 88:81, 29.97 tbr, 1k tbn, 1k tbc File
  
              > 'out2.flv' already exists. Overwrite ? [y/N] y w:352 h:288
  
              > pixfmt:yuv420p tb:1/1000000 sar:8/9 sws_param: 
  
      [image2 @ 0x551f880] decoding for stream 0 failed 
  
      [image2 @ 0x551f880] Could not find codec parameters (Video: png) 
  
      [movie @ 0x551f440] Failed to find stream info
  
      [movie @ 0x551f440] Failed to find any codec 
  
      Error initializing filter 'movie' with args 'watermark_logo352.png' 
  
      Error opening filters!

  When I use a jpg, it works like a charm.

  I'm use ffmpeg v 0.10.4 on Debian 6 Squeeze.
  Any help would be much appreciated.

  EDIT

  The problem is simpler than i thought. If i use ffmpeg -i with any png image i get a similar error :

    libavutil      51. 35.100 / 51. 35.100
  
    libavcodec     53. 61.100 / 53. 61.100
  
    libavformat    53. 32.100 / 53. 32.100
  
    libavdevice    53.  4.100 / 53.  4.100
  
    libavfilter     2. 61.100 /  2. 61.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0.  6.100 /  0.  6.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  [image2 @ 0xc8b73a0] decoding for stream 0 failed
  
  [image2 @ 0xc8b73a0] Could not find codec parameters (Video: png)
  
  watermark.png: could not find codec parameters