diff --git a/DSView/pv/data/decode/row.cpp b/DSView/pv/data/decode/row.cpp
index acab85bf..47425af6 100755
--- a/DSView/pv/data/decode/row.cpp
+++ b/DSView/pv/data/decode/row.cpp
@@ -22,6 +22,7 @@
 #include "row.h"
 
 #include <libsigrokdecode4DSL/libsigrokdecode.h>
+#include <assert.h>
 
 namespace pv {
 namespace data {
@@ -63,6 +64,8 @@ QString Row::title() const
 
 bool Row::operator<(const Row &other) const
 {
+    assert(_decoder);
+
     return (_decoder < other._decoder) ||
         (_decoder == other._decoder && _order < other._order);
 }
diff --git a/DSView/pv/data/decoderstack.cpp b/DSView/pv/data/decoderstack.cpp
index 1600d390..9964b117 100755
--- a/DSView/pv/data/decoderstack.cpp
+++ b/DSView/pv/data/decoderstack.cpp
@@ -65,7 +65,7 @@ DecoderStack::DecoderStack(pv::SigSession *session,
     _no_memory = false;
     _mark_index = -1;
     _decoder_status = decoder_status;
-    _stask_stauts = NULL; 
+    _stask_stauts = NULL;  
     
     _stack.push_back(new decode::Decoder(dec));
  
@@ -595,7 +595,7 @@ void DecoderStack::decode_data(const uint64_t decode_start, const uint64_t decod
 
 void DecoderStack::execute_decode_stack()
 {  
-	srd_session *session;
+	srd_session *session = NULL;
 	srd_decoder_inst *prev_di = NULL;
     uint64_t decode_start = 0;
     uint64_t decode_end = 0;
@@ -655,6 +655,7 @@ void DecoderStack::execute_decode_stack()
     if (error) {
         g_free(error);
     }
+
 	srd_session_destroy(session); 
 }
 
@@ -683,7 +684,7 @@ void DecoderStack::annotation_callback(srd_proto_data *pdata, void *self)
 	assert(d);
 
     if (st->_bStop){
-        qDebug()<<"decode task was stoped.";
+      //  qDebug()<<"decode task was stoped.";
         return;
     }
     if (d->_decoder_status == NULL){
diff --git a/DSView/pv/data/decoderstack.h b/DSView/pv/data/decoderstack.h
index d5e0c18a..c3093196 100755
--- a/DSView/pv/data/decoderstack.h
+++ b/DSView/pv/data/decoderstack.h
@@ -193,7 +193,7 @@ private:
     uint64_t        _sample_count; 
  
     decode_task_status  *_stask_stauts;    
-    mutable std::mutex _output_mutex;
+    mutable std::mutex _output_mutex; 
 
 	friend class DecoderStackTest::TwoDecoderStack;
 };
diff --git a/DSView/pv/sigsession.cpp b/DSView/pv/sigsession.cpp
index da710a2f..29de5dc6 100755
--- a/DSView/pv/sigsession.cpp
+++ b/DSView/pv/sigsession.cpp
@@ -430,6 +430,10 @@ void SigSession::start_capture(bool instant)
         return;
     }
 
+    // stop all decode tasks
+    int run_dex = 0;
+    clear_all_decode_task(run_dex);
+
     // stop previous capture
     stop_capture();
 
@@ -1366,7 +1370,12 @@ bool SigSession::add_decoder(srd_decoder *const dec, bool silent, DecoderStatus
         if (ret)
         { 
            _decode_traces.push_back(trace);
-            add_decode_task(trace);
+           
+            //add decode task from ui
+            if (!silent){
+                add_decode_task(trace);
+            }
+            
             signals_changed();
             data_updated();
         }
@@ -1917,7 +1926,7 @@ void SigSession::set_stop_scale(float scale)
   //the decode task thread proc
   void SigSession::decode_task_proc(){ 
 
-      //qDebug()<<"decode thread start";
+      qDebug()<<"------->decode thread start";
       auto task = get_top_decode_task();
       
       while (task != NULL)
@@ -1941,7 +1950,7 @@ void SigSession::set_stop_scale(float scale)
           task = get_top_decode_task();
       }  
 
-     // qDebug()<<"decode thread end";
+      qDebug()<<"------->decode thread end";
       _bDecodeRunning = false;
   }
 
diff --git a/libsigrokdecode4DSL/instance.c b/libsigrokdecode4DSL/instance.c
index a0f66be4..72fde30f 100755
--- a/libsigrokdecode4DSL/instance.c
+++ b/libsigrokdecode4DSL/instance.c
@@ -1229,8 +1229,9 @@ SRD_PRIV int srd_inst_decode(struct srd_decoder_inst *di,
 	if (!di->thread_handle) {
 		srd_dbg("No worker thread for this decoder stack "
 			"exists yet, creating one: %s.", di->inst_id);
+
 		di->thread_handle = g_thread_new(di->inst_id,
-						 di_thread, di);
+						 		di_thread, di);
 	}
 
 	/* Push the new sample chunk to the worker thread. */
diff --git a/libsigrokdecode4DSL/libsigrokdecode.h b/libsigrokdecode4DSL/libsigrokdecode.h
index bf180b55..1129d5d8 100755
--- a/libsigrokdecode4DSL/libsigrokdecode.h
+++ b/libsigrokdecode4DSL/libsigrokdecode.h
@@ -349,7 +349,7 @@ struct srd_proto_data {
 	uint64_t start_sample;
 	uint64_t end_sample;
 	struct srd_pd_output *pdo;
-	void *data;
+	void *data; 
 };
 struct srd_proto_data_annotation {
 	int ann_class;
diff --git a/libsigrokdecode4DSL/type_decoder.c b/libsigrokdecode4DSL/type_decoder.c
index 94beaefa..ea74cca8 100755
--- a/libsigrokdecode4DSL/type_decoder.c
+++ b/libsigrokdecode4DSL/type_decoder.c
@@ -463,7 +463,7 @@ static PyObject *Decoder_put(PyObject *self, PyObject *args)
 	uint64_t start_sample, end_sample;
 	int output_id;
 	struct srd_pd_callback *cb;
-	PyGILState_STATE gstate;
+	PyGILState_STATE gstate; 
 
 	py_data = NULL; //the fourth param from python