diff --git a/DSView/pv/data/logicsnapshot.cpp b/DSView/pv/data/logicsnapshot.cpp
index 9b059ef5..fd546df3 100644
--- a/DSView/pv/data/logicsnapshot.cpp
+++ b/DSView/pv/data/logicsnapshot.cpp
@@ -191,6 +191,8 @@ void LogicSnapshot::first_payload(const sr_datafeed_logic &logic, uint64_t total
     for (unsigned int i = 0; i < _channel_num; i++) {
         _last_sample[i] = *rd_data++;
         _last_calc_count[i] = 0;
+        _cur_ref_block_indexs[i].root_index = 0;
+        _cur_ref_block_indexs[i].lbp_index = 0;
     }
 
     append_payload(logic);
@@ -545,8 +547,10 @@ void LogicSnapshot::calc_mipmap(unsigned int order, uint8_t index0, uint8_t inde
         _ch_data[order][index0].tog |= 1ULL << index1;
     }
     else if (isEnd){
+        uint64_t ref_root = _cur_ref_block_indexs[order].root_index;
+        uint64_t ref_lbp  = _cur_ref_block_indexs[order].lbp_index;
 
-        if (_able_free)
+        if (_able_free || index0 > ref_root || (index0 == ref_root && index1 > ref_lbp))
             free(_ch_data[order][index0].lbp[index1]);
         else
             _free_block_list.push_back(_ch_data[order][index0].lbp[index1]);
@@ -596,6 +600,9 @@ const uint8_t *LogicSnapshot::get_samples(uint64_t start_sample, uint64_t &end_s
     else{
         if (lbp != NULL)
             *lbp = _ch_data[order][index0].lbp[index1];
+
+        _cur_ref_block_indexs[order].root_index = index0;
+        _cur_ref_block_indexs[order].lbp_index  = index1;
         
         return (uint8_t*)_ch_data[order][index0].lbp[index1] + offset;
     }
diff --git a/DSView/pv/data/logicsnapshot.h b/DSView/pv/data/logicsnapshot.h
index 1389d8b9..683e3ec4 100644
--- a/DSView/pv/data/logicsnapshot.h
+++ b/DSView/pv/data/logicsnapshot.h
@@ -31,7 +31,7 @@
 #include <vector>
 #include <map>
 
-#define CHANNEL_MAX_COUNT 512
+#define CHANNEL_MAX_COUNT 64
 
 namespace LogicSnapshotTest {
 class Pow2;
@@ -73,6 +73,12 @@ private:
         void *lbp[Scale];
     };
 
+    struct BlockIndex
+    {
+        uint64_t    root_index;
+        uint64_t    lbp_index;
+    };
+
 public:
     typedef std::pair<uint64_t, bool> EdgePair;
 
@@ -228,6 +234,7 @@ private:
     uint64_t    _loop_offset;
     bool        _able_free;
     std::vector<void*> _free_block_list;
+    struct BlockIndex _cur_ref_block_indexs[CHANNEL_MAX_COUNT];
  
 	friend class LogicSnapshotTest::Pow2;
 	friend class LogicSnapshotTest::Basic;