diff --git a/pythonlib/formats/srt.py b/pythonlib/formats/srt.py
index e0e83d3..6705b58 100644
--- a/pythonlib/formats/srt.py
+++ b/pythonlib/formats/srt.py
@@ -23,19 +23,25 @@ rTIME_STAMP_NO_HOUR = r"(\d+):(\d+)[.,](\d+)"
 def str_to_timestamp(time_stamp: str) -> TimeStamp:
     colon_cnt = time_stamp.count(":")
     if colon_cnt == 2:
-        times = [int(s) for s in re.findall(rTIME_STAMP, time_stamp)[0]]
-        hours = times[0]
-        minutes = times[1]
-        seconds = times[2]
-        milis = times[3]
-        milis = int(str(milis).ljust(3, '0'))
-    if colon_cnt == 1:
-        times = [int(s) for s in re.findall(rTIME_STAMP_NO_HOUR, time_stamp)[0]]
-        hours = 0
-        minutes = times[0]
-        seconds = times[1]
-        milis = times[2]
-        milis = int(str(milis).ljust(3, '0'))
+        # For HH:MM:SS.mmm
+        times = re.findall(rTIME_STAMP, time_stamp)
+        if times:
+            hours, minutes, seconds, milis_str = times[0]
+            hours, minutes, seconds = map(int, (hours, minutes, seconds))
+            milis = int((milis_str + "000")[:3])  # Normalize to 3 digits
+        else:
+            raise ValueError("Invalid time_stamp format for HH:MM:SS.mmm")
+
+    elif colon_cnt == 1:
+        # For MM:SS.mmm
+        times = re.findall(rTIME_STAMP_NO_HOUR, time_stamp)
+        if times:
+            minutes, seconds, milis_str = times[0]
+            minutes, seconds = map(int, (minutes, seconds))
+            milis = int((milis_str + "000")[:3])  # Normalize to 3 digits
+            hours = 0
+        else:
+            raise ValueError("Invalid time_stamp format for MM:SS.mmm")
     if colon_cnt == 0 or time_stamp.isspace():
         hours = 0
         minutes = 0