After looking at the spec sheet, while this camera appears to be a Dahua OEM, it is a 5MP camera on a 1/2.7" sensor which removes it from the optimal sensor/MP ratio range. It also might indicate that the firmware has been "played with" to provide acceptable low light video, IE slowing exposure, and that can also include frame and bit rates. I can say that all the authentic Dahua and the two non-Dahua cameras I have all maintain frame, iframe and bit rates under full daylight and at night. The only exceptions are the VTO and the DB1C which drop the iframe and bit rates depending on lighting.