// Reserved DSP message selector id's (second field of all 
// host&lt-&gtaudio system messages)
enum
{
  kMidiMsgArraySelRtId = 1000,
  kMidiSysExSelRtId,
  kUiDrvrSelRtId,     // cmUiDriverArg_t message to/from the UI driver
  kUiSelRtId,         // cmUiDriverArg_t message from the UI mgr to a client 
  kUiMstrSelRtId,     // indicates a cmDspUiHdr_t msg containing master control information for the audio system
  kStatusSelRtId,     // indicates the msg is of type cmRtSysStatus_t
  kNetSyncSelRtId,    // sent with a cmDspNetMsg_t object 
  kMsgSelRtId,        // client defined msg transmitted between threads or network nodes
};

typedef struct
{
  unsigned rtSubIdx;
  unsigned selId;   // Message selector id See kXXXSelRtId above
} cmRtSysMsgHdr_t;

// All of the UI messages that create a UI control contain an array of integers
// as in the 'value' field. The array contains the id's associated with
// the different programmable paramters which are part of the control.
// For example a slider control has minimum,maximum, step size, and value 
// parameters. The location in the array is hard coded according to the
// parameters meaning but the actual value of the id is left up to the 
// engine. This allows the engine to use whatever values work best for
// it on a per instance basis. 


// Header record for all messages between the host and the DSP controllers.
typedef struct
{
  cmRtSysMsgHdr_t hdr;
  unsigned     devIdx;
  unsigned     chIdx;
  bool         inFl;
  unsigned     ctlId;
  double       value;
} cmRtSysMstr_t;



// Control id's used to identify the control type of master contols.
enum
{
  kSliderUiRtId = 0,
  kMeterUiRtId  = 1,
  kMuteUiRtId   = 2,
  kToneUiRtId   = 3,
  kPassUiRtId   = 4
};


// Audio sub-system status record - this message can be transmitted to the host at
// periodic intervals.  See cmRtSysStatusNotifyEnable().
// When transmitted to the host this record acts as the message header.
// This header is followed by two arrays of doubles containing the input 
// and output meter values associated with the input and output audio devices.
// Message Layout: 
// [ rtSubIdx kStatusSelId cmRtSysStatus_t iMeterArray[iMeterCnt] oMeterArray[oMeterCnt] ]
typedef struct
{
  cmRtSysMsgHdr_t hdr;
  
  unsigned updateCnt;     // count of callbacks from the audio devices.
  unsigned wakeupCnt;     // count of times the audio system thread has woken up after the cond. var has been signaled by the audio update thread.
  unsigned msgCbCnt;      // count of msgs delivered via cmRtCallback() .
  unsigned audioCbCnt;    // count of times the DSP execution was requested via cmRtCallback(). 
  
  unsigned iDevIdx;       // Input device index
  unsigned oDevIdx;       // Output device index
  
  unsigned overflowCnt;   // count of times the audio input buffers overflowed
  unsigned underflowCnt;  // count of times the audio output buffers underflowed
  unsigned iMeterCnt;     // count of input meter channels
  unsigned oMeterCnt;     // count of output meter channels
  
} cmRtSysStatus_t;


typedef struct
{
  cmRtSysMsgHdr_t hdr;
  unsigned     devIdx;
  unsigned     portIdx;
  unsigned     msgCnt;
  // cmMidiMsg msgArray[msgCnt]
} cmRtSysMidi_t;

typedef struct
{
  cmRtSysMsgHdr_t    hdr;          // hdr.rtSubIdx = dest rtSubIdx hdr.selId = msg contents
  unsigned           dstEndPtId;   // = dest endpoint
  unsigned           srcEndPtId;   // = src endpoint id
  unsigned           srcNodeIdx;   // = src node index (filled in by receiving cmRtNet mgr)
  // char msg[ msgByteCnt ]
} cmRtNetMsg_t;