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• Send SDL frame to another process and display it

  18 septembre 2016, par Amit_sh

  I am trying to send a frame to another process in order to display it. I’m using dranger tutorial02.

  I was thinking to serialize the SDL_Overlay struct to bytes after the call to sws_scale, send it to the other process, deserialize it and call SDL_DisplayYUVOverlay to display it.

  Do you think this is my best choice ?

  If so, I’m having hard time serializing this struct.. here’s the code :

  size_t size_of_Overlay(SDL_Overlay *bmp) {
  
      /*
  
       * typedef struct  {
  
       *
  
       *  Uint32 format;
  
       *  int w, h;
  
       *  int planes;
  
       *  Uint16 *pitches;
  
       *  Uint8  **pixels;
  
       *  Uint32 hw_overlay:1; <- can I ignore it? cant point to a bit-field..
  
       *  
  
       *  } SDL_Overlay;
  
       */ 
  
       //      w,h,planes      format             pitches                pixels
  
      return sizeof(int)*3 + sizeof(Uint32) + sizeof(Uint16)*bmp->w + sizeof(Uint8)*bmp->h*3;
  
  }
  
  
  
  void overlay_to_buf(SDL_Overlay* bmp, char* buf) {
  
  
  
      if(!bmp || !buf) {
  
          perror("overlay_to_buf");
  
          exit(1);
  
      }
  
  
  
      memcpy(buf, &bmp->format, sizeof(Uint32));
  
      buf += sizeof(Uint32);
  
  
  
      memcpy(buf, &bmp->w, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      memcpy(buf, &bmp->h, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      memcpy(buf, &bmp->planes, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      memcpy(buf, bmp->pitches, sizeof(Uint16)*bmp->w);
  
      buf += sizeof(Uint16)*bmp->w;
  
  
  
      memcpy(buf, bmp->pixels[0], sizeof(Uint8)*bmp->h);  
  
      buf += sizeof(Uint8)*bmp->h;
  
  
  
      memcpy(buf, bmp->pixels[1], sizeof(Uint8)*bmp->h);  
  
      buf += sizeof(Uint8)*bmp->h;
  
  
  
      memcpy(buf, bmp->pixels[2], sizeof(Uint8)*bmp->h);  
  
      buf += sizeof(Uint8)*bmp->h;
  
  }
  
  
  
  
  
  void buf_to_overlay(SDL_Overlay *bmp, char* buf) {
  
  
  
      if(!bmp || !buf) {
  
          perror("buf_to_overlay");
  
          exit(1);
  
      }
  
  
  
      memcpy(&bmp->format, buf, sizeof(Uint32));
  
      buf += sizeof(Uint32);
  
  
  
      memcpy(&bmp->w, buf, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      memcpy(&bmp->h, buf, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      memcpy(&bmp->planes, buf, sizeof(int));
  
      buf += sizeof(int);
  
  
  
      bmp->pitches = (Uint16*)malloc(sizeof(Uint16)*bmp->w);
  
      memcpy(bmp->pitches, buf, sizeof(Uint16)*bmp->w);
  
      buf += sizeof(Uint16)*bmp->w;
  
  
  
      bmp->pixels[0] = (Uint8*)malloc(sizeof(Uint8)*bmp->h);
  
      memcpy(bmp->pixels[0], buf, sizeof(Uint8)*bmp->h);
  
      buf += sizeof(Uint8)*bmp->h;
  
  
  
      bmp->pixels[1] = (Uint8*)malloc(sizeof(Uint8)*bmp->h);
  
      memcpy(bmp->pixels[1], buf, sizeof(Uint8)*bmp->h);
  
      buf += sizeof(Uint8)*bmp->h;
  
  
  
      bmp->pixels[2] = (Uint8*)malloc(sizeof(Uint8)*bmp->h);
  
      memcpy(bmp->pixels[2], buf, sizeof(Uint8)*bmp->h);
  
      buf += sizeof(Uint8)*bmp->h;
  
  }

• Decoding of 4k video causing overflow of buffer in a multi process application

  15 octobre 2016, par mkreddy

  I am quite new in working with FFMPEG. Please excuse me if I made any mistake while explaining my problem.

  I am working on an application where PCAP captures 1316 bytes of data split that into 188 bytes and writes it into it to corresponding shared memory. The other process reads the data and decode using ffmpeg and process it.

  This whole process is working fine with H264 and HEVC video.
  The problem comes with 4k video. While decodig the 4k video I am encountering buffer overflow.
  I have observed that on a machine with high CPU frequence the overflow rate was less. Hence If I can reduce the time taken to decode and process the video data at ffmpeg might solve my problem. I am not able to find a good solution for my problem.

  Is there any way to speed up the process at ffmpeg decoder ?, is thre any other way to supress the overflows ?

• Elegant early exit from a spawned ffmpeg process in C

  21 octobre 2016, par jackson80

  I have a program where I build an ffmpeg command string to capture videos with options input through a gtk3 gui. Once I have all my options selected, I spawn a process with the ffmpeg command string. And I add a child watch to tell me when the process has completed.

    // Spawn child process 
  
    ret = g_spawn_async (NULL, argin, NULL, G_SPAWN_DO_NOT_REAP_CHILD, NULL, NULL, &pid1, NULL);
  
    if ( !ret )
  
    {
  
      g_error ("SPAWN FAILED");
  
      return;
  
    }
  
  
  
  /* Add watch function to catch termination of the process.  This function
  
     * will clean any remnants of process */
  
    g_child_watch_add (pid1, (GChildWatchFunc)cb_child_watch, widget );

  Executing ffmpeg from a terminal using a command line, the program will give an option to input a "q" at the terminal to end the ffmpeg process early.
  Is there any way to send a "q" to that spawned process to elegantly end the ffmpeg ? I’m fairly sure I could kill the process using the process id, but I would rather stop it using a mechanism that allows ffmpeg to gracefully exit..
  This is running Centos 7, kernel 4.7.5, ffmpeg version 3.0.2.
  Since I can still access the terminal where the ffmpeg output is displayed, I’ve tried typing a "q", but it has no effect on the process.