fix(dmr): avoid stale and mislabeled talkgroups

DMRDecoder.pas

@@ -166,6 +166,7 @@ type
     function GetLastBurst(var Dibits: array of Byte; out Sequence: QWord): Boolean;
 
     class function SyncKindName(Kind: TDMRSyncKind): string; static;
+    class function LinkControlTargetText(const S: TDMRStatus): string; static;
     property Enabled: Boolean read FEnabled;
     property OnAudio: TDMRAudioEvent read FOnAudio write FOnAudio;
   end;
@@ -580,6 +581,17 @@ begin
   FFixedNegativeOuter := 0;
   FFixedCenter := 0;
   FMobileActiveBurst := True;
+  // LC belongs to a call/slot, not to the tuned frequency forever. Keeping it
+  // across carrier loss made a newly acquired call briefly inherit the old
+  // target and display the same apparent TG on unrelated transmissions.
+  FillChar(FLinkControl, SizeOf(FLinkControl), 0);
+  FLastLCSlot := -1;
+  FSelectedSlot := -1;
+  FLastSelectedVoiceTick := 0;
+  FColorCodeValid := False;
+  FColorCode := 0;
+  FLastDataType := 0;
+  FSlotTypeCorrectedBits := 0;
   DMRMbeReset(FMbe);
 end;
 
@@ -947,4 +959,18 @@ begin
   end;
 end;
 
+class function TDMRDecoder.LinkControlTargetText(
+  const S: TDMRStatus): string;
+begin
+  Result := '';
+  if not S.LinkControlValid or (S.TargetID = 0) then Exit;
+  // ETSI Full Link Control opcode 0 is Group Voice Channel User; opcode 3 is
+  // Unit-to-Unit Voice Channel User. Other/vendor opcodes may reuse these 24
+  // bits for different data, so do not mislabel them as a talkgroup.
+  case S.LCOpcode of
+    0: Result := 'TG' + IntToStr(S.TargetID);
+    3: Result := 'ID' + IntToStr(S.TargetID);
+  end;
+end;
+
 end.

MainForm.pas

@@ -3606,7 +3606,7 @@ end;
 function TMainForm.DMRStatusText: string;
 var
   S: TDMRStatus;
-  Inv, Details: string;
+  Inv, Details, TargetText: string;
 begin
   if not FController.GetDMRStatus(S) then Exit('DMR unavailable');
   if not S.Enabled then Exit('DMR off');
@@ -3617,7 +3617,8 @@ begin
   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]);
+  TargetText := TDMRDecoder.LinkControlTargetText(S);
+  if TargetText <> '' then Details := Details + ' ' + TargetText;
   Result := Format('DMR %s%s%s #%d',
                    [TDMRDecoder.SyncKindName(S.SyncKind), Details, Inv,
                     S.SyncCount]);

PanafallPanel.pas

@@ -1382,7 +1382,7 @@ var
   I, Slot: Integer;
   O: TVfoOverlay;
   S: TDMRStatus;
-  Txt: string;
+  Txt, TargetText: string;
 begin
   if FController = nil then Exit;
   for I := 0 to High(FSliceFlags) do
@@ -1401,8 +1401,8 @@ begin
     else if S.CACHValid then Slot := S.Slot;
     if Slot in [0, 1] then Txt := 'DMR TS' + IntToStr(Slot + 1);
     if S.SlotTypeValid then Txt := Txt + ' CC' + IntToStr(S.ColorCode);
-    if S.LinkControlValid and (S.TargetID <> 0) then
-      Txt := Txt + ' TG' + IntToStr(S.TargetID);
+    TargetText := TDMRDecoder.LinkControlTargetText(S);
+    if TargetText <> '' then Txt := Txt + ' ' + TargetText;
     O.UpdateDMRStatus(Txt, True);
   end;
 end;