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• OpenCV to ffplay from named pipe (fifo)

  16 novembre 2016, par Betsalel Williamson

  I’ve been working on piping video from OpenCV in C++. I’ve tried to pipe the image after processing from OpenCV to a named pipe with the end goal of republishing the stream using a webserver either with VLC or a NodeJS server.

  Where I’m stuck is that the output from OpenCV doesn’t seem to be processing correctly. The video always has artifacts even though it should be the raw video.

  

  int main(int argc, char** argv)
  
  {
  
  
  
      VideoCapture camera(argv[1]);
  
  
  
      float fps = 15;
  
  
  
      // VLC raw video
  
      printf("Run command:\n\ncat /tmp/myfifo | cvlc --demux=rawvideo --rawvid-fps=%4.2f --rawvid-width=%.0f --rawvid-height=%.0f  --rawvid-chroma=RV24 - --sout \"#transcode{vcodec=h264,vb=200,fps=30,width=320,height=240}:std{access=http{mime=video/x-flv},mux=ffmpeg{mux=flv},dst=:8081/stream.flv}\""
  
          ,fps
  
          ,camera.get(CV_CAP_PROP_FRAME_WIDTH)
  
          ,camera.get(CV_CAP_PROP_FRAME_HEIGHT)
  
          );
  
  
  
  
  
      // ffplay raw video
  
      printf("Run command:\n\ncat /tmp/myfifo | ffplay -f rawvideo -pixel_format bgr24 -video_size %.0fx%.0f -framerate %4.2f -i pipe:"
  
          ,camera.get(CV_CAP_PROP_FRAME_WIDTH)
  
          ,camera.get(CV_CAP_PROP_FRAME_HEIGHT)
  
          ,fps
  
          );
  
  
  
      int fd;
  
      int status;
  
  
  
      char const * myFIFO = "/tmp/myfifo";
  
  
  
      if ((status = mkfifo(myFIFO, 0666)) < 0) { 
  
          // printf("Fifo mkfifo error: %s\n", strerror(errno)); 
  
          // exit(EXIT_FAILURE);
  
      } else {
  
          cout << "Made a named pipe at: " << myFIFO << endl;
  
      }
  
  
  
      cout << "\n\nHit any key to continue after running one of the previously listed commands..." << endl;
  
      cin.get();
  
  
  
      if ((fd = open(myFIFO,O_WRONLY|O_NONBLOCK)) < 0) {
  
          printf("Fifo open error: %s\n", strerror(errno));
  
          exit(EXIT_FAILURE);
  
      }   
  
  
  
      while (true)
  
      {
  
          if (waitKey(1) > 0)
  
          {
  
              break;    
  
          }
  
  
  
          Mat colorImage;
  
          camera >> colorImage; 
  
  
  
          // method: named pipe as matrix writes data to the named pipe, but image has glitch
  
          size_t bytes = colorImage.total() * colorImage.elemSize();
  
  
  
          if (write(fd, colorImage.data, bytes) < 0) {
  
              printf("Error in write: %s \n", strerror(errno)); 
  
          }            
  
      }
  
  
  
      close(fd);
  
  
  
      exit(EXIT_SUCCESS);
  
  }

• Live encoding with FFmpeg , decklink and pipe [duplicate]

  5 novembre 2016, par SKALIS

  This question already has an answer here :

  • Which pixel format for web mp4 video ?
    
    1 answer
    

  What is the best way to get live video input from a Blackmagic Decklink card and get it encoded with an external encoder (NvEncoder)

  I try :

  mkfifo output.yuv 
  
  ffmpeg  -f decklink  -r 30000/1000 -pix_fmt uyvy422  -i "DeckLink Mini Recorder 4K@24"  output.yuv 
  
  & NvEncoder -i output.yuv -pix_fmt yuv420p -bitrate 21M -fps30 output.ts

  Problem seems that the NvEncoder cannot take the uyvy422 format, so can I change that to yuv420p when capturing and before sending it trough the pipe ?

  The decklink card only can give me uyvy422

• How to pipe ppm data into ffmpeg from blender frameserver with while loop in PowerShell

  14 octobre 2016, par Radium

  Blender 2.6 manual features this little sh script for encoding a video from the Blender frameserver via ffmpeg. It works great on Windows with Cygwin, but only without -hwaccel hardware acceleration flag.

  #!/bin/sh
  
  BLENDER=http://localhost:8080
  
  OUTPUT=/tmp/output.ogv
  
  eval `wget ${BLENDER}/info.txt -O - 2>/dev/null |
  
      while read key val ; do
  
          echo R_$key=$val  
  
      done`
  
  i=$R_start
  
  {
  
      while [ $i -le $R_end ] ; do
  
         wget ${BLENDER}/images/ppm/$i.ppm -O - 2>/dev/null
  
         i=$(($i+1))
  
      done
  
  } | ffmpeg -vcodec ppm -f image2pipe -r $R_rate -i pipe:0 -b 6000k -vcodec libtheora $OUTPUT
  
  wget ${BLENDER}/close.txt -O - 2>/dev/null >/dev/null

  I’d like to encode my videos from Blender’s in Windows with -hwaccel dxva2 which works with PowerShell. I’ve begun converting the script to PowerShell but I have run into one last problem. I am having difficulty replicating this part of the script in PowerShell.

  i=$R_start
  
  {
  
      while [ $i -le $R_end ] ; do
  
         wget ${BLENDER}/images/ppm/$i.ppm -O - 2>/dev/null
  
         i=$(($i+1))
  
      done
  
  } | ffmpeg -vcodec ppm -f image2pipe -r $R_rate -i pipe:0 -b 6000k -vcodec libtheora $OUTPUT

  Below is my conversion to PowerShell.

  echo "gathering data";
  
  $blender = "http://localhost:8080";
  
  $output = "C:\Users\joel\Desktop\output.mp4";
  
  $webobj = wget $blender"/info.txt";
  
  $lines = $webobj.Content -split('[\r\n]') | ? {$_};
  
  $info = @{};
  
  foreach ($line in $lines) {
  
      $lineinfo = $line -split('[\s]') | ? {$_};
  
      $info[$lineinfo[0]] = $lineinfo[1];
  
  }
  
  echo $info;
  
  [int]$end = [convert]::ToInt32($info['end'],10);
  
  [int]$i = [convert]::ToInt32($info['start'],10);
  
  $video="";
  
  ( while ($i -le $end) {
  
      $frame = wget $blender"/images/ppm/"$i".ppm" > $null;
  
      echo $frame.Content > $null;
  
      $i++;
  
  } ) | ffmpeg -hwaccel dxva2 -vcodec ppm -f image2pipe -r $info['rate'] -i pipe:0 -b 6000k -vcodec libx264 $output;

  This is the piece I’m having trouble with. I’m not quite sure what the proper syntax is to pipe the data into the ffmpeg command in the same way as the bash script above.

  ( while( $i -le $end ) {
  
      $frame = wget $blender"/images/ppm/"$i".ppm" > $null;
  
      echo $frame.Content > $null;
  
      $i++;
  
  } ) | ffmpeg -hwaccel dxva2 -vcodec ppm -f image2pipe -r $info['rate'] -i pipe:0 -b 6000k -vcodec libx264 $output;

  Here is the output :

  PS C :\Users\joel\Desktop> .\encode.ps1
  gathering data
  Name                           Value
  
                             -----
  
  rate                           30
  
  height                         720
  
  ratescale                      1
  
  end                            57000
  
  width                          1280
  
  start                          1
  
  while : The term ’while’ is not recognized as the name of a cmdlet, function,
  
  script file, or operable program. Check the spelling of the name, or if a path
  
  was included, verify that the path is correct and try again.
  
  At C :\Users\joel\Desktop\encode.ps1:15 char:3
  
  + ( while ($i -le $end) 
  
  + 
  
      + CategoryInfo : ObjectNotFound : (while:String) [], CommandNotFoundException
  
      + FullyQualifiedErrorId : CommandNotFoundException