Transmission with Absolute Timing

The option MXF_TXAPERIODIC_FLAG_ABSOLUTE_START_TIME is used for starting a transmission at a specific start time in the future.

In this example, the transmission start time is based on the device clock + 100ms in the future, then the records are sent back-to-back.

#define MAX_TX_SUBFRAMES_TO_TRANSMIT     4

uint32                  rc;
HMXF_SERVER             server;
HMXF_DEVICE             device;
HMXF_CHANNEL            txChannel;
size_t                  txBufferSize;
HMXF_BUFFER             txBuffer;
MXF_A717_DATAREC*       rec;
uint64                  data;
uint64                  word, subframeSize=VMXF_A717_SUBFRAME_SIZE_128;
uint64                  currentTime;
uint64                  delay100ms = 100000;

                                  ...

   // Sets timebase to 64-bit microseconds
   if (!rc)
      rc = mxfSystemTimeBaseSet(server, MXF_TIMEBASE_DEVICE_USEC);   

   // Allocates buffer for tx data
   if(!rc)
   {
      txBufferSize = MAX_TX_SUBFRAMES_TO_TRANSMIT*sizeof(MXF_A717_DATAREC);

      // Allocates TX Aperiodic static buffer for HIGH priority queue
      rc=mxfTxAperiodicBufferAlloc(txChannel, MXF_TXAPERIODIC_PRIORITY_HIGH, txBufferSize, &txBuffer, NULL);

      // Host buffer allocation
      if(!rc)
      {
         txHostBuffer = (MXF_A717_DATAREC*) calloc(1, txBufferSize);
         if(!txHostBuffer)
            rc = MAXT_ERROR_MEM;
      }
   }

   if(!rc)
   {
      // Prepares string array
      rec = txHostBuffer;
      for(data=0; data<MAX_TX_SUBFRAMES_TO_TRANSMIT; data++)
      {
         rec->timeTag      = 0;
         rec->control      = 0;
         rec->dataSize     = 2 * (uint32)subframeSize; // 16 bits per word in subframe
         rec->repeatCount  = 1;
         rec->reserved     = 0;
         for(word=0; word < subframeSize; word++)
         {
            if (word == 0)
            {
               // 1st word of each subframe has to be a sync word
               // sync words are: 
               // - 0x247 for subframe #0 
               // - 0x5B8 for subframe #1
               // - 0xA47 for subframe #2 
               // - 0xDB8 for subframe #3
               switch (data%4)
               {
               case 0:
                  rec->data[word] = 0x247;
                  break;
               case 1:
                  rec->data[word] = 0x5B8;
                  break;
               case 2:
                  rec->data[word] = 0xA47;
                  break;
               case 3:
                  rec->data[word] = 0xDB8;
                  break;
               default:
                  break;
               }
            }
            else
               rec->data[word] = (uint16)(0x11*word);
         }
         rc = mxfA717NextDataRecordPtrGet(rec, &rec);
      }
   }

   // Gets the current time
   if(!rc)
      rc = mxfDeviceTimerGet(device, &currentTime);  

   if(!rc)
   {
      printf("Transmitting ...\n");
      // Transmits records with absolute start time
      rc = mxfA717TxAperiodicWrite(txBuffer, MXF_TXAPERIODIC_FLAG_ABSOLUTE_START_TIME, currentTime+delay100ms, MAX_TX_SUBFRAMES_TO_TRANSMIT, txHostBuffer);
   }

                                        ...