DIS-2/M StreamerPro HDD Large UTP
40
Dallmeier electronic
Bitrate
The bit rate is a measure of the degree of compression of video data; it thus has a direct
impact on the image quality of the recording. A low bit rate stands for a high degree of
compression with a relatively small volume of data but poor image quality.
A high bit rate stands for a low degree of compression with a relatively large volume of data
and very good image quality.
A bit rate of between 4 and 6 Mbit/s (megabit per second) is a good compromise between
data volume and image quality. Most requirements in surveillance systems are met with the
quality of image thus obtained.
Bitrate mode
The bit rate mode allows you to configure video recording to occur at a constant or a
variable bit rate. A variable bit rate makes better use of the available hard disk space.
The variable setting changes the bit rate in accordance with the activity (changes) in the
image. You can limit the fluctuation of the bit rate by making the appropriate setting, which
is done as a percent.
Example to bit rate mode
With a set bit rate of 4 Mbit/s and a bit rate mode “variable by 50%“, the bit rate can
vary from 6 Mbit/s to 2 Mbit/s during recording.
In variable bit rate mode, settings are made in 10% increments, from 10% to 400%.
IMPORTANT
When the Bitrate is changed, all images recorded up to this
point are erased.
Resolution
The resolution enables you to influence the size of the images for the video signal. The
entries are made using the H.261/CIF (Common Intermediate Format) and define length x
width in pixels.
GOP-size
The GOP size (GOP = Group Of Pictures) describes way in which pictures are used to
generate the MPEG data stream.
The higher the GOP size, the better the picture quality, although a higher GOP size will also
result in an increase in the delay. A GOP size between 6 and 15 generally represents a good
compromise.
As from a GOP size of 6 the use of B Frames can be enabled by checking the appropriate
checkbox. This setting also has a positive effect on the picture quality, but again results in
a slight delay.
GOP sizes greater than 15 belong to the Extended GOPs. Please note that reverse playback
is only possible in reduced quality (by frame drops) when these GOP sizes are used.
