fix(dmr): track voice state per timeslot

DMRDecoder.pas

@@ -113,11 +113,12 @@ type
     FCurrentBurstPos: Integer;
     FLastBurst: TDMRDibitBurst;
     FLastBurstInfo: TDMRBurstInfo;
-    FLastLinkControl: TDMRLinkControl;
+    FLinkControl: array[0..1] of TDMRLinkControl;
     FLastLCSlot: Integer;
     FColorCodeValid: Boolean;
     FColorCode, FLastDataType, FSlotTypeCorrectedBits: Integer;
     FSelectedSlot: Integer;
+    FLastSelectedVoiceTick: QWord;
     FVoiceFrameCount, FVoiceErrorCount: QWord;
     FOnAudio: TDMRAudioEvent;
     FBurstCount: QWord;
@@ -280,13 +281,14 @@ begin
     FillChar(FCurrentBurst, SizeOf(FCurrentBurst), 0);
     FillChar(FLastBurst, SizeOf(FLastBurst), 0);
     FillChar(FLastBurstInfo, SizeOf(FLastBurstInfo), 0);
-    FillChar(FLastLinkControl, SizeOf(FLastLinkControl), 0);
+    FillChar(FLinkControl, SizeOf(FLinkControl), 0);
     FLastLCSlot := -1;
     FColorCodeValid := False;
     FColorCode := 0;
     FLastDataType := 0;
     FSlotTypeCorrectedBits := 0;
     FSelectedSlot := -1;
+    FLastSelectedVoiceTick := 0;
     FVoiceFrameCount := 0;
     FVoiceErrorCount := 0;
     DMRMbeReset(FMbe);
@@ -487,7 +489,6 @@ begin
   end;
   if FLastBurstInfo.LinkControl.Decoded then
   begin
-    FLastLinkControl := FLastBurstInfo.LinkControl;
     if (FSyncKind in [dskBSData, dskBSVoice]) and
        FLastBurstInfo.CACH.Valid then
       FLastLCSlot := FLastBurstInfo.CACH.Slot
@@ -495,7 +496,12 @@ begin
       FLastLCSlot := 1
     else
       FLastLCSlot := 0;
-    if FSelectedSlot < 0 then FSelectedSlot := FLastLCSlot;
+    FLinkControl[FLastLCSlot] := FLastBurstInfo.LinkControl;
+    if FSelectedSlot < 0 then
+    begin
+      FSelectedSlot := FLastLCSlot;
+      FLastSelectedVoiceTick := GetTickCount64;
+    end;
   end;
   DecodeVoiceBurst;
   Inc(FBurstCount);
@@ -508,6 +514,7 @@ var
   PCM: array[0..DMR_PCM_SAMPLES - 1] of Single;
   MbeResult: TDMRMbeResult;
   Slot, FrameIndex, RC: Integer;
+  NowTick: QWord;
 begin
   if (FMbe = nil) or (FLastSyncTick = 0) or
      (GetTickCount64 - FLastSyncTick > DMR_SYNC_HOLD_MS) then Exit;
@@ -521,8 +528,20 @@ begin
   end
   else if FSyncKind = dskDirectTS2Voice then Slot := 1
   else Slot := 0;
-  if FSelectedSlot < 0 then FSelectedSlot := Slot;
+  NowTick := GetTickCount64;
+  if (FSelectedSlot < 0) or
+     ((Slot <> FSelectedSlot) and (FLastSelectedVoiceTick <> 0) and
+      (NowTick - FLastSelectedVoiceTick > 1000)) then
+  begin
+    FSelectedSlot := Slot;
+    DMRMbeReset(FMbe);
+  end;
   if Slot <> FSelectedSlot then Exit;
+  FLastSelectedVoiceTick := NowTick;
+  // Service Options bit 6 denotes privacy/encryption. mbelib cannot decrypt
+  // it, so suppress the characteristic digital noise while retaining IDs.
+  if FLinkControl[Slot].Decoded and
+     ((FLinkControl[Slot].ServiceOptions and $40) <> 0) then Exit;
 
   DMRExtractAMBEFrames(FLastBurst, Frames);
   for FrameIndex := 0 to 2 do
@@ -576,6 +595,7 @@ end;
 procedure TDMRDecoder.GetStatus(out S: TDMRStatus);
 var
   NowTick: QWord;
+  LCStatusSlot: Integer;
 begin
   FillChar(S, SizeOf(S), 0);
   NowTick := GetTickCount64;
@@ -608,12 +628,19 @@ begin
       S.ColorCode := FColorCode;
       S.DataType := FLastDataType;
       S.SlotTypeCorrectedBits := FSlotTypeCorrectedBits;
-      S.LinkControlValid := FLastLinkControl.Decoded;
-      S.LCSlot := FLastLCSlot;
-      S.LCOpcode := FLastLinkControl.Opcode;
-      S.ServiceOptions := FLastLinkControl.ServiceOptions;
-      S.TargetID := FLastLinkControl.TargetID;
-      S.SourceID := FLastLinkControl.SourceID;
+      LCStatusSlot := FSelectedSlot;
+      if (LCStatusSlot < 0) or not FLinkControl[LCStatusSlot].Decoded then
+        LCStatusSlot := FLastLCSlot;
+      S.LinkControlValid := (LCStatusSlot >= 0) and
+                            FLinkControl[LCStatusSlot].Decoded;
+      S.LCSlot := LCStatusSlot;
+      if S.LinkControlValid then
+      begin
+        S.LCOpcode := FLinkControl[LCStatusSlot].Opcode;
+        S.ServiceOptions := FLinkControl[LCStatusSlot].ServiceOptions;
+        S.TargetID := FLinkControl[LCStatusSlot].TargetID;
+        S.SourceID := FLinkControl[LCStatusSlot].SourceID;
+      end;
       S.SelectedSlot := FSelectedSlot;
       S.VoiceFrameCount := FVoiceFrameCount;
       S.VoiceErrorCount := FVoiceErrorCount;

MainForm.pas

@@ -3594,7 +3594,8 @@ begin
   if not S.Synced then Exit(Format('DMR sync... %.3f', [S.SignalRMS]));
   if S.Inverted then Inv := ' INV' else Inv := '';
   Details := '';
-  if S.CACHValid then Details := Format(' TS%d', [S.Slot + 1]);
+  if S.LinkControlValid then Details := Format(' TS%d', [S.LCSlot + 1])
+  else if S.CACHValid then Details := Format(' TS%d', [S.Slot + 1]);
   if S.SlotTypeValid then
     Details := Details + Format(' CC%d/DT%d', [S.ColorCode, S.DataType]);
   if S.LinkControlValid then Details := Details + Format(' TG%d', [S.TargetID]);