时间戳处理新增接口支持获取相对时间戳

src/Common/Stamp.cpp

@@ -20,6 +20,15 @@ using namespace toolkit;
 
 namespace mediakit {
 
+int64_t DeltaStamp::relativeStamp(int64_t stamp) {
+    _relative_stamp += deltaStamp(stamp);
+    return _relative_stamp;
+}
+
+int64_t DeltaStamp::relativeStamp(){
+    return _relative_stamp;
+}
+
 int64_t DeltaStamp::deltaStamp(int64_t stamp) {
     if(!_last_stamp){
         //第一次计算时间戳增量,时间戳增量为0

src/Common/Stamp.h

@@ -28,9 +28,12 @@ public:
      * @return 时间戳增量
      */
     int64_t deltaStamp(int64_t stamp);
+    int64_t relativeStamp(int64_t stamp);
+    int64_t relativeStamp();
 
 private:
     int64_t _last_stamp = 0;
+    int64_t _relative_stamp = 0;
 };
 
 //该类解决时间戳回环、回退问题