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• OpenCV to ffplay from named pipe (fifo)

  13 juillet 2017, 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);
  
  }

• All audios should be played after combing using ffmpeg. But there is only audio for the first part

  6 mai 2020, par Eric Z

  This code is combining 3 mp4 files using ffmpeg command. Each file has audio. 
After combining, I can listen audio for only first part. 
How can I solve this problem ?

  



  ===========================================================================

  



  ffmpeg -y -i "tmp/titled-0c33a83dc70534c67f66.mp4" -i "tmp/titled-1c2fc9a95e644ab135a3.mp4" -i "tmp/titled-73c3fb1a3ea435cacdd2.mp4" -i "logo/logo.png"  -filter_complex "
nullsrc=s=1280x720[bg];
[0:v]setpts=PTS-STARTPTS+0/TB[v0];
[1:v]setpts=PTS-STARTPTS+4.039/TB[v1];
[2:v]setpts=PTS-STARTPTS+8.078/TB[v2];
[bg][v0]overlay=x='if(lte(t,4.039),0,min(0,-w*min(1,max(0,0.98*(t-4.039)^2))))':y=0,trim=duration=13.145[bg];
[bg][v1]overlay=x='if(gte(t,8.078),-w*min(1,max(0,0.98*(t-8.078)^2)),max(0,1280*(1-min(1,max(0,0.69*(atan(8*(t-4.039)^2.7)))))))':y=0[bg];
[bg][v2]overlay=x='max(0,1280*(1-min(1,max(0,0.69*(atan(8*(t-8.078)^2.7))))))':y=0"
-y -vcodec h264 -crf 13 -acodec aac -strict -2 "out.mp4"


  


• Segmentation fault when media played using libavcodec

  20 août 2013, par sarah john

  Myself trying to play media using libavcodec as backend.I downloaded ffmpeg-2.0.1 and installed using ./configure,make and make install.
  While trying to run an application to play an audio file, i'm getting segmentation fault while checking for the first audio stream.my program is like

  AVFormatContext* container = avformat_alloc_context();
  
  if (avformat_open_input(&container, input_filename, NULL, NULL) < 0) {
  
      die(“Could not open file”);
  
  }
  
  
  
  if (av_find_stream_info(container) < 0) {
  
      die(“Could not find file info”);
  
  }
  
  
  
  av_dump_format(container, 0, input_filename, false);
  
  int stream_id = -1;
  
  int i;
  
  
  
  for (i = 0; i < container->nb_streams; i++) {
  
      if (container->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO) {
  
          stream_id = i;
  
          break;
  
      }
  
  }

  Segmentation fault occurs at if(container->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO)

  How can i fix this ? I am working in ubuntu 12.04.