func: static void mmap_release_buffer(AVPacket *pkt)
  
  {
  
      struct v4l2_buffer buf;
  
      int res, fd;
  
      struct buff_data *buf_descriptor = pkt->priv;
  
  
  
      if (pkt->data == NULL)
  
          return;
  
  
  
      memset(&buf, 0, sizeof(struct v4l2_buffer));
  
      buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  
      buf.memory = V4L2_MEMORY_MMAP;
  
      buf.index = buf_descriptor->index;
  
      fd = buf_descriptor->fd;
  
      av_free(buf_descriptor);
  
  
  
      res = ioctl(fd, VIDIOC_QBUF, &buf);
  
      if (res < 0)
  
          av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n",
  
                 strerror(errno));
  
  
  
      pkt->data = NULL;
  
      pkt->size = 0;
  
  }
  