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• OpenCL YUV420P black pixel

  30 avril 2021, par Albert Tinon

  I'm working on an FFmpeg OpenCL filter for converting GoPro Max .360 files in Google EAC projected files.
For doing that I need to "stack" the 2 input streams to a twice height output.
It is working very well at a realtime speed. (The working code is in comment)

  


  For going further I need to replace some pixels with some specific colors.
I wrote some macros for making RGB->YUV conversion. But I get only some green or pink pixel (only grey is OK).
this is my test code (with stacking in comment)

  


  #define Y(R,G,B) 0.299 * R + 0.587 * G + 0.114 * B
#define U(R,G,B) -0.147 * R - 0.289 * G + 0.436 * B
#define V(R,G,B) 0.615 * R - 0.515 * G - 0.100 * B
#define YUV(R,G,B) (float4)(Y(R,G,B),U(R,G,B),V(R,G,B),0)

__kernel void gopromax_stack(__write_only image2d_t dst,
                                __read_only  image2d_t gopromax_front,
                                __read_only  image2d_t gopromax_rear)
{
    const sampler_t sampler = (CLK_NORMALIZED_COORDS_FALSE |
                               CLK_FILTER_NEAREST);
    
    float4 val;
    int2 dst_size = get_image_dim(dst);
    int2 loc = (int2)(get_global_id(0), get_global_id(1));
    int split_loc = dst_size.y/2;

        if (loc.y < split_loc)
        {
          // working code for stacking
          //  val = read_imagef(gopromax_front, sampler, (int2)(loc.x, loc.y));

          // testing to put grey (working)
            val = YUV(0.5f,0.5f,0.5f);
        }
        else
        {
          // working code for stacking
          //  val = read_imagef(gopromax_rear, sampler, (int2)(loc.x, loc.y-split_loc));

          // testing to put black (gives green !)
            val = YUV(0,0,0);
        }

    if ((loc.xcode>

  


  I tried many think I cannot succeed to generate black or anything except grey.
What did I make wrong ?
I supposed that my pixels are YUV because I specified yuv420p as the format in my filter :

  


  -filter_complex '[0:0]format=yuv420p,hwupload[a] , [0:4]format=yuv420p,hwupload[b], [a][b]gopromax_opencl, hwdownload,format=yuv420p'


  


  The source streams are in hevc / nv12.

  


  Thanks all for your help.

  


• avcodec/tiff : check the black level denominator

  26 octobre 2019, par James Almer

  avcodec/tiff : check the black level denominator
  Fixes ticket #8327.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/tiff.c

• using ffmpeg to resize video with black bars

  23 juillet 2018, par Jens S

  i have a video with resolution 720:576 and i want it to have the ratio 16:9, e.g. 1024:576 with black bars on the sides. don’t know if it matters, but i am working with ffmpeg for windows. After research i tried the solution i found on 2 related questions :

  -i .\video.mp4 -vf scale=1024:576:force_original_aspect_ratio=decrease,pad=1024:576:(ow-iw)/2:(oh-ih)/2,setsar=1 out.mp4

  but i get an output that "ow-iw" was not recognized. Here is the complete output. unfortunatly it is in german(as am i) if u tell me how to change the output language i will provide it in english :

  ow-iw : Die Benennung "ow-iw" wurde nicht als Name eines Cmdlet, einer Funktion, einer Skriptdatei oder eines ausführbaren Programms erkannt. Überprüfen Sie die Schreibweise des
  
  Namens, oder ob der Pfad korrekt ist (sofern enthalten), und wiederholen Sie den Vorgang.
  
  In Zeile:1 Zeichen:119
  
  + ... :576:force_original_aspect_ratio=decrease,pad=1024:576:(ow-iw)/2:(oh- ...
  
  +                                                             ~~~~~
  
      + CategoryInfo          : ObjectNotFound: (ow-iw:String) [], CommandNotFoundException
  
      + FullyQualifiedErrorId : CommandNotFoundException