diff --git a/picamera2/devices/imx500/imx500.py b/picamera2/devices/imx500/imx500.py
index ef9518c7..ee944e78 100644
--- a/picamera2/devices/imx500/imx500.py
+++ b/picamera2/devices/imx500/imx500.py
@@ -581,14 +581,11 @@ def __get_input_tensor_info(self, tensor_info) -> tuple[str, int, int, int]:
 
     @staticmethod
     def get_kpi_info(metadata: dict) -> Optional[tuple[float, float]]:
-        """Return the KPI parameters in the form (dnn_runtime, dsp_runtime)."""
+        """Return the KPI parameters in the form (dnn_runtime, dsp_runtime) in milliseconds."""
         kpi_info = metadata.get('CnnKpiInfo')
         if kpi_info is None:
             return None
-        if type(kpi_info) not in [bytes, bytearray]:
-            kpi_info = bytes(kpi_info)
-
-        dnn_runtime, dsp_runtime = struct.unpack('II', kpi_info)
+        dnn_runtime, dsp_runtime = kpi_info[0], kpi_info[1]
         return dnn_runtime / 1000, dsp_runtime / 1000
 
     def __set_network_firmware(self, network_filename: str):