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Bit Rate Type: There are two options: "Variable" and "Fixed".
If you select variable bit rate, DVR will adjust the actual bit rate according to the video
movement. When there is not much movement, DVR will use low bit rate, while there is much
movement, DVR will use high bit rate. In this case, DVR can save HDD usage and network
bandwidth.
If you select fixed bit rate, DVR will use the fixed bit rate to compress iamge. The bit rate
size is defined in "Max Bit Rate" option. In this case, we can calculate the recorded file size and
network bandwidth that we need.
Max Bit Rate: If you select variable bit rate, when the video input has great movement, we
need to limit the max bit rate. The max bit rate has following options (bps): 32K, 48K, 64K, 80K,
96K, 128K, 160K, 192K, 224K, 256K, 320K, 384K, 448K, 512K, 640K, 768K, 896K, 1M, 1.25M,
1.5M, 1.75M, 2M and "User define".
The max bit rate selection has relations with resolution. If you select high resolution, you
must select high bit rate. For CIF resolution, the typical max bit rate is 384K-768Kbps. For DCIF
resolution, the typical bit rate is 512K-1Mbps. For 4CIF resolution, the typical bit rate is
1.25Mbps-1.75Mbps. Of course, you will select the proper max bit rate based on the camera,
background and image quality requirement.
Bit rate: You can select bit rate size for fixed bit rate type. It is the same as "Max Bit Rate".
Image Quality: If you select variable bit rate type, you can define image quality. There are 6
options: Highest, Higher, High, Average, Low and Lowest. High image quality needs high bit rate
size.
Frame Rate: Frame per second. Options are: Full (PAL is 25 FPS and NTSC is 30FPS), 20,
16, 12, 10, 8, 6, 4, 2, 1, 1/2, 1/4, 1/8, 1/16. For low frame rate, you can select low bit rate size.
PreRecord Time: When you enable motion detection recording or external alarm recording,
you can define prerecord time. The options are: No PreRecord, 5 Seconds (default selection), 10
Seconds, 15 Seconds, 20 Seconds, 25 Seconds, 30 Seconds and Max PreRecord.
MaxPreRecord is to save all data in PreRecord buffer. The PreRecord time is related with bit
rate. The lower bit rate, the longer PreRecord time is.
If the bit rate (Max bit rate) is very low, and you select "PreRecord Time" as "5 Seconds",
maybe the actual perrecord time is more than 5 seconds. On the other side, if the bit rate is high,
and set "PreRecord Time" as "30 Seconds", the actual prerecord time maybe is less than 30
seconds.
PostRecord Time: When external alarm or motion alarm is stopped, DVR will continue
recording time. The options are: 5 Seconds (default), 10 Seconds, 30 Seconds, 1 Minute, 2
Minutes, 5 Minutes and 10 Minutes.
User Manual of NVR Series DVR
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