Channel Class

Accessing a physical HDLC channel requires a handle to the channel.

A channel handle is a reference to a channel holding a physical resource (port). The channel handle is the first argument to be passed to many MXF channel oriented functions.

To get the handle to an HDLC physical port regardless of the devices installed, use the mxfModuleChannelGet() function by specifying the physical port index.

You can also use the mxfModuleChannelAllGet() function with the chnClass argument MXF_CLASS_HDLC.

If MXF_DEVICE_ALL is specified with the mxfSystemDeviceAllGet() function, all handles of detected devices are returned.

{
HMXF_SERVER server=0;
HMXF_DEVICE device;
HMXF_MODULE module;
HMXF_CHANNEL rx[4];
uint32 rc;
uint64 deviceCount;
uint64 moduleCount;
uint64 channelCount;
uint64 device     = MXF_DEVICE_ALL;          // All devices
uint64 moduleType = MXF_MODULE_MULTI_EH;     // Multi module
uint64 chnClass   = MXF_CLASS_HDLC;          // HDLC channel class
uint64 subClass   = MXF_SCLASS_RX_CHANNEL;   // RX channel

   // Connects to the local server
   rc = mxfServerConnect("0.0.0.0", "", "", FALSE, &server);
   if (rc)
   {
      printf("Error connection 0x%08lx", rc);
      return rc;
   }
   // Inits MXF library
   rc = mxfSystemInit(server);
   if (!rc)
   {
      // Gets the device handle
      rc = mxfSystemDeviceAllGet(server, device, 1, &deviceCount, &device);
      if (!rc && deviceCount)
      {
         // Gets the module handle
         rc = mxfDeviceModuleAllGet(device, moduleType, 1, &moduleCount, &module);

         // Gets the channel handle
         if (!rc && moduleCount)
            rc = mxfModuleChannelAllGet(module, chnClass, subClass, 4, &channelCount, rx);
       }
   }
}

Changing channel class

On multi module, HDLC channel can by default be configured on another channel class. To configure a channel to HDLC, an initialization callback set with the mxfSystemInitAttributeUint64CallbackHandler() function can be used.
Since MXF 4.5.2, it is now possible to change the channel class by using mxfAttributeUint64Set() with KMXF_CHANNEL_CLASS attribute instead of using the initialization handler.
It is a good programming practice to avoid relying on the default channel class value (or any other attributes for that matter) and set it to the desired value.