Dahua NVR21-4KS3 Series User Manual page 204

Parameter
Resolution
Frame Rate (FPS)
Bit Rate Type
Quality
I Frame Interval
Bit Rate (Kb/S)
Step 3 Click More.
Description
Select resolution for the video.
The maximum video resolution might be different depending on your
device model.
Configure the frames per second for the video. The higher the value is,
the clearer and smoother the image will become. Frame rate changes
along with the resolution.
Generally, in PAL format, you can select the value from 1 through 25; in
NTSC format, you can select the value from 1 through 30. However, the
actual range of frame rate that you can select depends on the
capability of the Device.
● CBR (constant bit rate): The bit rate changes slightly around the
defined value. We recommended selecting CBR when there might
be only small changes in the monitoring environment.
● VBR (variable bit rate): The bit rate changes with monitoring
scenes. Select variable stream when there might be big changes in
the monitoring environment.
● ABR (average bit rate): When selecting ABR, you need to configure
Max Bit Rate and ABR.
The connected camera needs to support the average bit rare.
The bigger the value is, the better the image will become.
This parameter is available if you select VBR as Bit Rate Type.
The interval between two reference frames.
● Main stream: The higher the value, the better the image quality.
● Sub stream: For constant stream, the bit rate changes near the
defined value; for variable stream, the bit rate changes along with
the image but the maximum value still stays near the defined
value.
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User's Manual