Transmission with Record Timing

Transmission with record timing means the records are scheduled on the time tag set for each record.

Each time tag specifies a clock value defining when the record must be transmitted.

The option MXF_TXAPERIODIC_FLAG_USE_RECORD_ABSOLUTE_TIME must be used for this type of transmission.

In the example below, the records are sent based on the absolute clock timing specified in the time tag field for each record.

#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;
      }
   }

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

   currentTime += delay100ms;   

   if(!rc)
   {
      // Prepares string array
      rec = txHostBuffer;
      for(data=0; data<MAX_TX_SUBFRAMES_TO_TRANSMIT; data++)
      {
         rec->timeTag      = currentTime+(data*1000000); // 1 second between each record
         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);
      }
   }

   if(!rc)
   {
      printf("Transmitting ...\n");
      // Transmits records with record absolute time
      rc = mxfA717TxAperiodicWrite(txBuffer, MXF_TXAPERIODIC_FLAG_USE_RECORD_ABSOLUTE_TIME, 0, MAX_TX_SUBFRAMES_TO_TRANSMIT, txHostBuffer);
   }

   ...