For what it is worth attached is a bulletin from Hikvision. Bit rate plays an important role in the quality of the picture. Isn’t that the point of getting megapixel cameras in the first place, to improve the quality and definition in the picture?
NOTE:
Video quality is NOT the same as resolution. Resolution is measured in height and width.
An Image or video clip can be at very high resolution while being at a very low quality.
The higher your data stream / bit rate is, the better the video quality.
The lower your data stream / bit rate is, the lower your video quality.
These instructions are for general reference only. There are many other factors affecting file size,
such as the amount of motion, the complexity of the scene, lighting, etc.
Bit-rate is determined by:
The selected resolution (1280x720, 1920x1080, 2560x1920, etc.)
Frame rate (frames per second)
Video Quality (The amount of compression being applied to each camera.)