allow overriding of group voice channel data in IOSP_GRP_VCH; make sure to instantiate values to sane defaults;

src/common/p25/lc/TSBK.cpp

@@ -100,6 +100,8 @@ TSBK::TSBK() :
     m_response(P25_RSP_ACCEPT),
     m_netId(P25_WACN_STD_DEFAULT),
     m_sysId(P25_SID_STD_DEFAULT),
+    m_grpVchId(0U),
+    m_grpVchNo(0U),
     m_emergency(false),
     m_encrypted(false),
     m_priority(4U),

src/common/p25/lc/tsbk/IOSP_GRP_VCH.cpp

@@ -42,7 +42,8 @@ using namespace p25;
 /// <summary>
 /// Initializes a new instance of the IOSP_GRP_VCH class.
 /// </summary>
-IOSP_GRP_VCH::IOSP_GRP_VCH() : TSBK()
+IOSP_GRP_VCH::IOSP_GRP_VCH() : TSBK(),
+    m_forceChannelId(false)
 {
     m_lco = TSBK_IOSP_GRP_VCH;
 }
@@ -93,7 +94,7 @@ void IOSP_GRP_VCH::encode(uint8_t* data, bool rawTSBK, bool noTrellis)
         (m_emergency ? 0x80U : 0x00U) +                                             // Emergency Flag
         (m_encrypted ? 0x40U : 0x00U) +                                             // Encrypted Flag
         (m_priority & 0x07U);                                                       // Priority
-    if (m_grpVchId != 0U) {
+    if ((m_grpVchId != 0U) || m_forceChannelId) {
         tsbkValue = (tsbkValue << 4) + m_grpVchId;                                  // Channel ID
     }
     else {

src/common/p25/lc/tsbk/IOSP_GRP_VCH.h

@@ -53,6 +53,10 @@ namespace p25
 
                 /// <summary>Returns a string that represents the current TSBK.</summary>
                 virtual std::string toString(bool isp = false) override;
+
+            public:
+                /// <summary>Flag forcing the use of the group voice channel ID regardless of value.</summary>
+                __PROPERTY(bool, forceChannelId, ForceChannelId);
             };
         } // namespace tsbk
     } // namespace lc