Dahua NVR4108-P User Manual page 240

Please refer to the following sheet for detailed information.
Parameter
Channel
Video enable
Code stream
type
Compression
Resolution
Frame Rate
Bit Rate
Figure 5-21
Function
Please select a channel from the dropdown list.
Check the box here to enable extra stream video. This item is
enabled by default.
It includes main stream, motion stream and alarm stream. You
can select different encode frame rates form different recorded
events.
System supports active control frame function (ACF). It allows
you to record in different frame rates.
For example, you can use high frame rate to record important
events, record scheduled event in lower frame rate and it allows
you to set different frame rates for motion detection record and
alarm record.
The main bit stream supports H.264. The extra stream supports
H.264, MJPG.
The resolution here refers to the capability of the network
camera.
PAL：1～25f/s；NTSC：1～30f/s.

Main stream: You can set bit rate here to change video
quality. The large the bit rate is, the better the quality is.
Please refer to recommend bit rate for the detailed
information.

Extra stream: In CBR, the bit rate here is the max value.
In dynamic video, system needs to low frame rate or
video quality to guarantee the value. The value is null in
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