Optelecom-nkf Siqura C-54 E-MC User Manual page 47

Using the internal web pages
Quantization matrix
Note on quantization: Quantization is a lossy compression technique used in image processing. It is
based on the fact that variations in high frequency brightness, for example, are not easily distinguished
by the human eye. A quantization matrix, a combination of predefined values, is used to reduce the
amount of information in the high frequency components of an image, thereby making the stream more
compressible. The values in a quantization matrix are often chosen such that certain frequencies are
kept in the source to avoid losing image quality.
Stream manager
Peaks in the network load vary with encoder output. Use the Stream manager to balance
network load. It can limit the output rate per stream sent to the transmitters. Be warned
that setting Stream bandwidth limit to a lower value may introduce latency, because peaks
in the encoder output will be buffered.
Stream bandwidth
limit
Keep alive interval
Low latency
Note on Low Latency mode: This mode may cause packet loss in the network. As a rule of thumb, the
average load of an Ethernet port should not exceed 40% of its maximum load (i.e. 40 MB for a 100 MB
port). When Low Latency mode is disabled, this may increase to 60%.
Available matrixes include MPEG Default, Alternative 1, and
Alternative 2
Figure 7.17 Advanced section, Stream manager settings
[0...100000] kbit/s. Sets the maximum bit rate per stream sent to
the transmitters. This will serve to spread bursts but in its turn may
give rise to latency, e.g. when handling large I-frames. The total
outgoing bit rate of the two MPEG-2/4, MJPEG encoders and the Live
View encoder should not exceed 15 Mbit/s. The Stream bandwidth
limit mechanism is disabled when Low latency (see below) is
selected. See also figure 7.19.
[10 ... 100000] milliseconds. The frequency for sending keep alive
messages to the encoder.
Raises the output bandwidth limit to allow for peaks in the network
load. To be selected if you need to keep the delay between the input
and output of images as short as possible, for improved tracking with
a dome camera, for example. Selecting Low latency disables the
Stream bandwidth limit mechanism (see above).
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