重构点播，回放，下载时ssrc不一致以及TCP主动播放的逻辑

src/main/java/com/genersoft/iot/vmp/utils/DateUtil.java

@@ -7,6 +7,7 @@ import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.time.format.DateTimeParseException;
+import java.time.temporal.ChronoUnit;
 import java.time.temporal.TemporalAccessor;
 
 import java.util.Locale;
@@ -106,4 +107,9 @@ public class DateUtil {
         LocalDateTime nowDateTime = LocalDateTime.now();
         return formatterISO8601.format(nowDateTime);
     }
+
+    public static long getDifferenceForNow(String keepaliveTime) {
+        Instant beforeInstant = Instant.from(formatter.parse(keepaliveTime));
+        return ChronoUnit.MILLIS.between(beforeInstant, Instant.now());
+    }
 }