Using the VideoEdge IP Encoder with Intellex IP

Using the VideoEdge IP Encoder with Intellex IP
This application note explains the tradeoffs inherent in using IP video and
provides guidance on optimal configuration of the VideoEdge IP encoder with
Intellex IP. The VideoEdge IP Encoder is a high performance video encoder
capable of serving multiple video streams at 4CIF resolution and up to 30 images
per second per stream. The VideoEdge IP Encoder is the first video encoder
using American Dynamics Active Content Compression (ACC) that is compatible
with the Intellex IP Digital Video Management System. The new combination of
Intellex IP, Network Client and VideoEdge IP Encoder provides a powerful new
solution for security applications.
IP Video Basics
IP video uses Ethernet to transmit the video information from the IP encoder (or
IP camera) and the Intellex IP unit. To accomplish this, first the analog video
signal is digitized in the encoder and then compressed using the ACC
compression algorithm. The VideoEdge IP uses a Digital Signal Processor (DSP)
to perform the compression and network functions. Once the image data is
compressed it is treated just like any other digital information on the network and
is transported across the network using the TCP-IP protocol. Once it is received
by the Intellex IP the digital video information is decompressed (so that it can be
displayed live locally or with Network Client) and then selected frames are
recompressed for storage. One new capability available with the VideoEdge IP
Encoder is that the live image display rate can be different than the image record
rate. The live rate is configured on the IP Sources setup screen in Intellex IP and
the record rate is set up on the Rate setup screen on the Intellex IP. The record
rate is limited to be less than or equal to the live rate. Compressing and
decompressing the digital video is a significant load on the DSP in the encoder
and the CPU in the Intellex IP.
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Configuring the VideoEdge IP Encoder with Intellex IP
The overall system performance is largely determined by how the encoder and
Intellex IP are configured to work together. Configuring the VideoEdge IP
Encoder for use with Intellex IP involves setting the capture parameters on the
encoder and setting the record parameters on the Intellex IP. The encoder
settings determine the live image characteristics and the record settings affect
characteristics of the playback video on the Intellex IP. There are some factors
that must be considered when configuring these products to work as a system:
•
The encoder settings determine the live image quality and the upper limit
of the record image quality.
•
The encoder settings and image motion (or noise) affect the encoder DSP
loading.
•
The encoder settings determine the amount of data loading the network.
•
The encoder settings and image motion (or noise) have the greatest
impact on Intellex IP CPU loading.
•
The total load on the Intellex IP CPU is determined by:
o Encoder settings
o Image motion and noise
o The record settings on the Intellex IP
o Driving a local monitor with Intellex IP
o Number of Network Client connections
Each of these factors will be considered separately.
Encoder Settings
The VideoEdge IP Encoder can be configured to set the image capture rate,
resolution, and compression quality for each of the video inputs. The settings
available are:
•
Rate: 1 ips to 30 ips
•
Resolution: CIF, 2CIF, 4CIF (with/without deinterlacing)
•
Quality: Super, Normal, Extended Record
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•
Motion Sensitivity: High, Normal
The VideoEdge IP Encoder is capable of capturing, compressing, and
transmitting 30 ips per video input at the highest resolution and quality settings
for low to moderate levels of motion on each camera for a total of 120 ips. As the
motion becomes more severe, the load on the DSP increases until the maximum
image rate begins to drop off at the highest resolution and quality settings. An
example of high motion would be panning cameras on some or all of the video
inputs.
When the image resolution is 2CIF or less the image rate is 120 ips regardless of
the quality settings or the amount of motion. Where ever possible it is important
to mix the fixed cameras and domes between the encoders so that no more than
three cameras on a single encoder can be panning at any one time.
Each Video Edge IP encoder can support multiple connections, so that a user
can record data on Intellex IP, while using a browser for live viewing. Remember
that each connection adds to the load on the encoder DSP and will limit the total
image rate. (Network Client connections add load to the Intellex IP but do not
affect the loading on the encoder.)
Recommendations
•
Mix fixed cameras and domes on each VideoEdge IP Encoder to reduce
the chances of simultaneous severe motion on all cameras connected to a
single encoder.
•
Minimize the number of connections to each encoder and if multiple
connections are necessary reduce the resolution, rate, and quality on the
backup connections.
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•
Avoid using cameras that get very noisy in the dark in day/night situations.
Select a camera that delivers a usable image under the expected lighting
conditions.
Network Data
The network bandwidth required for each VideoEdge IP Encoder also depends
on the configuration settings of the encoder and the amount of image motion.
Table 1 summarizes the amount of network traffic per camera under motion and
still image conditions. The network traffic is in bits per second per camera at 30
ips.
Table 1
Panning
Camera
No Motion
4CIF Super/High
4CIF Super/High
De-interlacing Enabled
De-interlacing Disabled
6.6 Mb/sec
6 Mb/sec
2.8 Mb/sec
1.2 Mb/sec
1.2 Mb/sec
210 Kb/sec
2CIF Normal/Normal
There is a 29X increase on the network traffic between no motion at 2CIF and
high motion at 4CIF! And the network traffic from 16 cameras could saturate a
100Mbit network! It is important when designing the network transporting the
video data to isolate the encoders with a high quality gigabit switch so that the
traffic on the 100 Mbit segments is minimized.
Recommendations
•
Use quality Gigabit switches to isolate the network traffic.
•
Use a dedicated network (not the corporate network) for video data.
•
Use one of the Intellex IP NICs for the encoders and IP cameras and the
other NIC for Network Client.
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Intellex IP CPU Loading
The CPU load on the Intellex IP is determined by all of the configuration settings
but some have more effect than others. Table 2 lists the typical incremental CPU
loading for each of several system settings.
Frames will be
dropped once the
loads exceeds 100%.
Table 2: Incremental CPU load
The greatest CPU load is handling the 240 images per second coming from the
connected encoders. The next highest load is driving the main monitor and
sending images to Network Client. In this scenario it would be possible to receive
240 ips of 4 CIF images, record 120 ips of 4CIF images and either display live on
the main monitor (CPU loading 83%) or display live on Network Client (CPU
loading 83%) but not both (CPU loading 103%). As the CPU load approaches
100% the Intellex IP drops frames being served to the Network Client for live
display and drops frames from recording. Two important things to minimize the
CPU load on the Intellex IP are to 1) configure the encoders to deliver the
minimum live rate necessary for the application, and 2) configure the Intellex IP
with the main monitor disabled if live surveillance is not being done or if live
surveillance is via Network Client. The main monitor can be disabled by enabling
classic security and logging out of the Intellex.
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Recommendations
•
Limit the total encoder image rate to 240 4CIF ips per system. This would
be 4 encoders at 15 ips per camera or two encoders at 30 ips.
•
Try to balance resolutions, rates, and expected scene motion across the
encoders and Intellex IP units where possible.
•
Enable security and log out of Intellex if local live surveillance is not
needed in order to reduce CPU load. Disconnecting the VGA monitor does
not drop the CPU load.
Performance on Legacy Intellex IP Platforms
Intellex IP was built on a Dell PowerEdge 750 server prior to July 2007. After July
2007, the platform is a Dell PowerEdge 860 server. The older server can be
upgraded to Intellex software version 4.12 but the performance will be limited
because of processor and motherboard limitations. Unfortunately, hardware
upgrades are not practical for the PowerEdge 750. In general, the CPU loading is
twice as high on the PowerEdge 750 compared to the PowerEdge 860 under the
same conditions of live rate, resolution, and record rate. The difference between
the PowerEdge 750 and 860 models is that the PowerEdge 750 has a floppy
drive in the right hand drive bay and a single USB connector in front, while the
PowerEdge 860 has no floppy drive and dual USB connectors in front.
Recommendations
•
Limit upgraded PowerEdge 750 servers to two VideoEdge IP encoders per
server.
•
Limit the encoder image rate (the live rate) to 15 ips per camera.
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