diff --git a/src/cmAudDsp.c b/src/cmAudDsp.c
index 4b97570..213a7dd 100644
--- a/src/cmAudDsp.c
+++ b/src/cmAudDsp.c
@@ -354,10 +354,15 @@ cmAdRC_t _cmAdParseSysJsonTree( cmAd_t* p )
     {
       cmAudioSysArgs_t*   asap        = &p->asCfgArray[i].cfg.ssArray[j].args;
       const cmJsonNode_t* argsNodePtr = cmJsonArrayElementC(ssArrayNodePtr,j);
+      
+      asap->inDevIdx    = cmInvalidIdx;
+      asap->outDevIdx   = cmInvalidIdx;
+      asap->inDevLabel  = NULL;
+      asap->outDevLabel = NULL;
 
       if((jsRC = cmJsonMemberValues( argsNodePtr, &errLabelPtr,
-          "inDevIdx",           kIntTId,  &asap->inDevIdx,
-          "outDevIdx",          kIntTId,  &asap->outDevIdx,
+          "inDevLabel",         kStringTId,  &asap->inDevLabel,
+          "outDevLabel",        kStringTId,  &asap->outDevLabel,
           "syncToInputFl",      kTrueTId, &asap->syncInputFl,
           "msgQueueByteCnt",    kIntTId,  &asap->msgQueueByteCnt,
           "devFramesPerCycle",  kIntTId,  &asap->devFramesPerCycle,
@@ -443,6 +448,35 @@ cmAdRC_t _cmAdCreateAggDevices( cmAd_t* p )
   return rc;
 }
 
+cmAdRC_t _cmAdResolveDeviceLabels( cmAd_t* p )
+{
+  cmAdRC_t rc = kOkAdRC;
+  unsigned i,j;
+  
+  // for each cmAsAudioSysCfg record in audioSysCfgArray[]
+  for(i=0; i<p->asCfgCnt; ++i)
+  {
+    // for each audio system sub-subsystem 
+    for(j=0; j<p->asCfgArray[i].cfg.ssCnt; ++j)
+    {
+      cmAudioSysArgs_t*   asap        = &p->asCfgArray[i].cfg.ssArray[j].args;
+      if((asap->inDevIdx = cmApDeviceLabelToIndex( asap->inDevLabel )) == cmInvalidId )
+      {
+        rc = cmErrMsg(&p->err,kInvalidAudioDevIdxAdRC,"The audio input device '%s' could not be found.", cmStringNullGuard(asap->inDevLabel));
+        goto errLabel;
+      }
+      
+      if((asap->outDevIdx = cmApDeviceLabelToIndex( asap->outDevLabel )) == cmInvalidId )
+      {
+        rc = cmErrMsg(&p->err,kInvalidAudioDevIdxAdRC,"The audio input device '%s' could not be found.", cmStringNullGuard(asap->inDevLabel));
+        goto errLabel;
+      }
+    }
+  }
+ errLabel:
+  return rc;
+}
+
 cmAdRC_t _cmAdCreateNrtDevices( cmAd_t* p )
 {
   cmAdRC_t rc = kOkAdRC;
@@ -721,10 +755,11 @@ cmAdRC_t cmAudDspAlloc( cmCtx_t* ctx, cmAdH_t* hp, cmMsgSendFuncPtr_t cbFunc, vo
   if((rc = _cmAdParseSysJsonTree(p)) != kOkAdRC )
     goto errLabel;
 
+ 
   // create the aggregate device
   if( _cmAdCreateAggDevices(p) != kOkAdRC )
     goto errLabel;
-
+  
   // create the non-real-time devices
   if( _cmAdCreateNrtDevices(p) != kOkAdRC )
     goto errLabel;
@@ -740,6 +775,12 @@ cmAdRC_t cmAudDspAlloc( cmCtx_t* ctx, cmAdH_t* hp, cmMsgSendFuncPtr_t cbFunc, vo
     goto errLabel;
   }
 
+  if( _cmAdResolveDeviceLabels(p) != kOkApRC )
+  {
+    rc = cmErrMsg(&p->err,kAudioPortFailAdRC,"Audio device labels could not be resolved..");
+    goto errLabel;
+  }
+
   // initialize the audio buffer
   if( cmApBufInitialize( cmApDeviceCount(), p->meterMs ) != kOkApRC )
   {
diff --git a/src/cmAudDsp.h b/src/cmAudDsp.h
index 152c94e..6e0c88b 100644
--- a/src/cmAudDsp.h
+++ b/src/cmAudDsp.h
@@ -27,7 +27,8 @@ extern "C" {
     kAggDevCreateFailAdRC,
     kNrtDevSysFailAdRC,
     kAfpDevSysFailAdRC,
-    kNetSysFailAdRC
+    kNetSysFailAdRC,
+    kInvalidAudioDevIdxAdRC
   };
 
 
diff --git a/src/cmAudioNrtDev.c b/src/cmAudioNrtDev.c
index c22f770..1408df3 100644
--- a/src/cmAudioNrtDev.c
+++ b/src/cmAudioNrtDev.c
@@ -189,6 +189,10 @@ cmApRC_t cmApNrtAllocate( cmRpt_t* rpt )
 cmApRC_t cmApNrtFree()
 {
   cmApRC_t rc = kOkApRC;
+  
+  if( _cmNrt == NULL )
+    return rc;
+  
   cmApNrtDev_t* dp = _cmNrt->devs;
   while( dp != NULL )
   {
diff --git a/src/cmAudioSys.h b/src/cmAudioSys.h
index 9a5b28e..7fc5c8d 100644
--- a/src/cmAudioSys.h
+++ b/src/cmAudioSys.h
@@ -130,16 +130,18 @@ extern "C" {
   // Audio device sub-sytem configuration record 
   typedef struct cmAudioSysArgs_str
   {
-    cmRpt_t*       rpt;               // system console object
-    unsigned       inDevIdx;          // input audio device
-    unsigned       outDevIdx;         // output audio device
-    bool           syncInputFl;       // true/false sync the DSP update callbacks with audio input/output
-    unsigned       msgQueueByteCnt;   // Size of the internal msg queue used to buffer msgs arriving via cmAudioSysDeliverMsg().
-    unsigned       devFramesPerCycle; // (512) Audio device samples per channel per device update buffer.
-    unsigned       dspFramesPerCycle; // (64)  Audio samples per channel per DSP cycle.
-    unsigned       audioBufCnt;       // (3)   Audio device buffers.
-    double         srate;             // Audio sample rate.
-    int            srateMult;         // Sample rate multiplication factor (negative for divide)
+    cmRpt_t*        rpt;               // system console object
+    const cmChar_t* inDevLabel;        // input audio device text label
+    const cmChar_t* outDevLabel;       // output audio device text label
+    unsigned        inDevIdx;          // input audio device index
+    unsigned        outDevIdx;         // output audio device index 
+    bool            syncInputFl;       // true/false sync the DSP update callbacks with audio input/output
+    unsigned        msgQueueByteCnt;   // Size of the internal msg queue used to buffer msgs arriving via cmAudioSysDeliverMsg().
+    unsigned        devFramesPerCycle; // (512) Audio device samples per channel per device update buffer.
+    unsigned        dspFramesPerCycle; // (64)  Audio samples per channel per DSP cycle.
+    unsigned        audioBufCnt;       // (3)   Audio device buffers.
+    double          srate;             // Audio sample rate.
+    int             srateMult;         // Sample rate multiplication factor (negative for divide)
   } cmAudioSysArgs_t;
 
   // Audio sub-system configuration record.