Recherche avancée

Sur d’autres sites (12836)

• apngdec : use side data to pass extradata to the decoder

  1er novembre 2016, par Andreas Cadhalpun

  apngdec : use side data to pass extradata to the decoder
  Fixes remuxing apng streams coming from the apng demuxer.
  
  This is a regression since 940b8908b94404a65f9f55e33efb4ccc6c81383c.
  Found-by : James Almer <jamrial@gmail.com>
  
  Reviewed-by : James Almer <jamrial@gmail.com>
  
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  

  • [DH] libavcodec/pngdec.c
  • [DH] libavformat/apngdec.c

• ffmpeg in child process doesn't exit when parent closes pipe

  28 mars 2013, par user2221129

  This code snippet is from a pthread process. It is responsible for reading configuration/options to pass to ffmpeg. The data piped to ffmpeg is coming in on a ring buffer of video frames (as a proof of concept, in the final implementation these would be coming from a camera device). The parent writes to the child via a pipe established with dup2. The problem I'm having is that most of the time, the ffmpeg process doesn't seem to recognize the pipe has been closed by the parent (as strace shows the ffmpeg is in read). There are probably some unhandled mutex situations.

  #define CHILD_READ  writepipe[0]
  
  #define PARENT_WRITE    writepipe[1]
  
  #define MAX_VIDEO_BUFFERS 30
  
  
  
  static int last_frame_written = -1;
  
  static int buffer_size = -1;
  
  static void *video_buffer[MAX_VIDEO_BUFFERS];
  
  
  
  #define MAXTHREADS 2
  
  static pthread_t thread[MAXTHREADS];
  
  static int sigusr[MAXTHREADS];
  
  static int sigusr_thread[MAXTHREADS];
  
  
  
  #define MAXPARAMETERS 100
  
  
  
  void* encoder_thread(void *ptr)
  
  {
  
      int param;
  
      const char **parameters = new const char* [MAXPARAMETERS];
  
      ssize_t bytes_written_debug = 0;
  
  
  
      int writepipe[2] = {-1,-1};
  
      int last_frame_read = -1;
  
      pid_t   childpid;
  
  
  
      // xxx
  
      if ( 0 != pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL) )
  
      {
  
          fprintf(stderr,"pthread_setcancelstate could not be set\n");
  
      }
  
  
  
      param = *(int*)ptr;
  
      fprintf(stderr,"param = %d\n", param);
  
  
  
      switch (param)
  
      {
  
          ...read config file and populate parameters for child call...
  
      }
  
  
  
      while ( last_frame_written == -1 )
  
      {
  
          fprintf(stderr,"ENCODER THREAD WAITING\n");
  
          sleep(1);
  
      }
  
  
  
      if ( pipe(writepipe) < 0 )
  
      {
  
          ...handle error case...
  
      }
  
  
  
  
  
      if ( (childpid = fork()) < 0)
  
      {
  
          fprintf(stderr,"child failed\n");
  
      }
  
      else if ( 0 == childpid )   /* in the child */
  
      {
  
          dup2(CHILD_READ,  STDIN_FILENO);
  
          //close(CHILD_READ); // doesn't seem to matter
  
          close(PARENT_WRITE);
  
  
  
          execv("/usr/bin/ffmpeg",(char **)parameters);
  
          return;
  
      }
  
      else                /* in the parent */
  
      {
  
          fprintf(stderr,"THREAD CHILD PID: %d\n",childpid);
  
          close(CHILD_READ);
  
  
  
          while ( last_frame_written > -1 && 0==sigusr_thread[param] )
  
          {
  
              if ( last_frame_read != last_frame_written )
  
              {
  
                  // send frame to child (ffmpeg)
  
                  last_frame_read = last_frame_written;
  
                  bytes_written_debug = write(PARENT_WRITE,video_buffer[last_frame_read], buffer_size);
  
                  if ( bytes_written_debug < 0 )
  
                  {
  
                      fprintf(stderr, "write error\n");
  
                      break;
  
                  }
  
              }
  
  
  
              usleep(10000); // assume ~100Hz rate
  
          }
  
  
  
  /// Problems begin now: no more data from main process,
  
  /// Shouldn't this close "close" the pipe created with dup2 and hence EOF ffmpeg?
  
          if ( close(PARENT_WRITE) )
  
          {
  
              fprintf(stderr,"\n\nclose failure! wtf?\n\n\n");
  
          }
  
  
  
  // debug sleep:
  
  // waiting 10 sec doesn't seem to help...
  
  // trying to give ffmpeg some time if it needs it
  
          sleep(10);
  
  
  
  // kill never fails here:
  
          if ( !kill(childpid,SIGINT) )
  
          {
  
              fprintf(stderr, "\n\nkill child %d\n", childpid);
  
          }
  
          else
  
          {
  
              fprintf(stderr, "\n\nkill failed for child %d\n", childpid);
  
          }
  
  
  
          fprintf(stderr,"\n\nwaiting\n\n\n");
  
          int status = 0;
  
  
  
  // wait forever (in most cases); ps -axw shows all the ffmpeg's
  
          wait(&status);
  
      }
  
  }
  
  
  
  
  
  
  
  
  
  int main()
  
  {
  
      ...
  
      for ( int i = 0; i < MAXTHREADS; ++i)
  
      {
  
          sigusr[i] = 0;
  
          sigusr_thread[i] = 0;
  
          param[i] = i;
  
          iret = pthread_create( &thread[i], NULL, encoder_thread, (void*) &param[i] );
  
      }
  
      ...
  
  
  
      // Maybe this is important to the pthread signaling?
  
      // Don't think so because thread's SIGINT isn't picked up by signal handler (not shown)
  
      sigemptyset(&set);
  
      sigaddset(&set, SIGHUP);
  
      sigaddset(&set, SIGINT);
  
      sigaddset(&set, SIGUSR1);
  
      sigaddset(&set, SIGUSR2);
  
      sigaddset(&set, SIGALRM);
  
  
  
      /* block out these signals */
  
      sigprocmask(SIG_BLOCK, &set, NULL);
  
  
  
      ...read file/populate frame buffer until file exhausted...
  
  
  
      fprintf(stderr, "waiting for threads to exit\n");
  
  
  
      for ( int i = 0; i < MAXTHREADS; ++i)
  
      {
  
          sigusr_thread[i] = 1;
  
          pthread_join( thread[i], NULL);
  
      }
  
      fprintf(stderr, "done waiting for threads to exit\n");
  
  
  
      ...
  
  
  
      return 0;
  
  }

  I've embedded comments and questions in the thread's parent code after the frame buffer read/write loop.

  Hope I've provided enough detail - stackoverflow posting noob ! Thank you.

• Generate a .JSON file in After Effects or Premiere ?

  9 avril 2021, par Ryan

  I am working on a video template app where users can pick a video template and add their images as background layer and render a .mp4 video.

  


  Each template which I upload to the server is a Zip file which consists of 4 elements
1 : Background Video
2 : Source Images
3 : Output Video
4 : .JSON file

  


  I am a motion designer and not good with code, however when I check the .JSON file, I can tell that its holding some sort of animation data, I can see the text pointing towards the source images and the background video and a bunch of other text data which I think is basically animating the source images.

  


  Now being a motion designer, I can make some really nice animation overlays and simply replace it with the BACKGROUND VIDEO element and yes it works. And I can make as many animation templates I want using this one .JSON file.

  


  However (This is where the limitation starts), even though I can have really exciting overlay animations, the base source images are just 3 images fading in and out, and this data is coming from the .JSON file.

  


  What would be really nice, is if I could some how create/generate my own .JSON files, this way I can have the source images animate however I like (Position, Scale, Rotate) but I have no clue how this .JSON can be generated.

  


  This link has the main files which make up one template. You can check the .JSON file and how it works with other elements.
One Template Files