*Reducing network and client load
Technical Article | TA-20201002-TP-46 VDG Sense | Tutorials | Video Streaming | |
Introduction
VDG Sense has several techniques to reduce network traffic between server and client and to reduce the (CPU) load on operator stations when viewing many cameras. VDG Sense uses the streaming capabilities of the cameras itself to achieve this. There are three ways to achieve a more efficient use of resources:
Multi Streaming
Sense can request multiple video streams (high resolution and low resolution) from the camera. Depending on the size of the panel in which the camera is viewed, either the high or low resolution stream is displayed. See also this article about how to configure: Multi streamingMulticast
Video streams flow directly from cameras to operator stations (Sense clients) using multicast networking mechanism. Note that with unicast networking all the video streams flow first from camera to Sense server and then to Sense client. With multicast this ‘bottleneck’ is not there.Multi Streaming in combination with Multicast
Above options can also be combined to balance the network load even more evenly and remove network ‘bottlenecks’.
When to use Multi Streaming or Multicast
When to use multi streaming is explained in more detail here: Multi streaming
Multicast streaming is best used in a system where many operator stations (Sense clients) are used simultaneously and each is using multi camera layout. I.e. many video panels in one layout.
If unicast would be used in this scenario a ‘bottleneck’ will occur at the Sense server (master or slave) since all video data first flows from camera to Sense server and then from Sense server to Sense client.
For example: Assume there are 50 Sense clients each showing 25 low resolution video streams (cameras) with 1Mbit/s stream bandwidth each. Now also assume these 25 cameras are all configured on the same Sense server. This server then must already push 50 * 25 * 1 Mbit/s = 1.25 Gbit/s of network traffic out. This is already exceeding the common 1 Gbit maximum of modern network cards.
To overcome this, multicast networking should be used. In that case the camera sends out its video data to a specific multicast group (special IP address range) in the network (switch / router). Each operator station (Sense client) that needs to display the video of this camera can then ‘subscribe’ to this multicast group and will receive the video directly and not via the Sense server. All this is done via the standardized IGMP protocol.
When designing an installation and one has doubts about what technique(s) to use, common questions are:
Operator wants to view many cameras simultaneously on a single operator station?
Multi Streaming could be used, this reduces system load (CPU and memory) of operator station and reduces network load between server and clientMany operator stations displaying the same set of cameras?
Multicast could be used, this reduces network load from server to clientNetwork traffic between servers and clients need to be reduced?
Either multi streaming or multicast can be usedTwo or more servers (parks) need to record video from the same cameras (redundant setup)?
Multicast needs to be used. Based on experience it is advised to not have multiple unicast connections active on same camera. It can lead to camera ‘overloading’ and unwanted video artifacts like hick-ups and stuttering. Multicast is advised for this.
Configuring Multi Streaming
How to configure Multi streaming is described in following article: Multi streaming
Configuring Multicast
Multicast can only be enabled if the device supports it and if Sense supports it for that device. There are also differences in the type of multicast streaming supported by Sense. Depending on the cameratype, Sense will show the option “Enable Multicast” in the device’s advanced settings tab (Read more). To enable multicast check “Enable Multicast” checkbox.
For cameras which only support direct streaming or passive multicast the following settings will be available (e.a. VDG):
Multicast Address
The multicast address of the camera
Multicast Port
The multicast port of the camera
For the VDG camera the settings to enable multicast should be like this:
For cameras which support both RTSP multicast and direct streaming or passive multicast the following settings will be available (e.a Siqura, ONVIF):
RTSP (auto)
Depending on the camera type this option is available or not. Using ‘RTSP (auto)’ the Multicat Address’ and ‘Multicast Port’ will be not available. Using this mode the actual multicast address is retrieved from the camera using RTSP negotiation. VDG Sense also does not change or configure any values in the camera itself.
RTSP (manual)
Depending on the camera type this option is available or not. Using ‘RTSP (manual)’ the settings ‘Multicat Address’ and ‘Multicast Port’ will be available. They need to correspond to the multicast settings in the camera. There is no negotiation with the camera about which multicast address and port should be used. VDG Sense also does not change or configure any values in the camera itself.
Multicast Address
The multicast address of the camera
Multicast Port
The multicast port of the camera
Below is an example of a Siqura Eve device settings page where both options could be configured.
In VDG Sense ‘Direct Streaming’ corresponds with ‘RTSP Manual’ mode and ‘RTSP (Multicast)’ corresponds with ‘RTSP (Auto)’. It is adivsed to disable ‘Direct Streaming’ if RTSP Multicast is used because it could conflict with each other.
Dual streaming & Multicasting
Dual streaming and multicasting can also be enabled simultaneously. In the ‘Stream 2’ settings the multicast checkbox and settings need to be configured:
Camera compatibility
Some camera brands which support dual streaming, require an additional in-camera configuration or the ‘Stream Profile’ in VDG Sense needs to be configured.
Samsung Wisenet III
A stream profile called ‘DUAL’ needs to be configured in the camera configutation. It is not require to fill in the ‘Stream Profile’ setting in VDG Sense. The procedure to add the stream profile is this:
Open the device web configuration page
Click the ‘Setup’ tab
By default, the “Video profile” page should be opened
Create a new profile and name it ‘DUAL’ (case sensitive, without quotes)
Click ‘Apply’
Siqura 1000/1100 series
For Siqura 1000/1100 series the ‘Stream Profile’ for the second stream needs to be set to ‘subStream’ (without the quotes).
Grundig 1
For Grundig 1 series the ‘Stream Profile’ for the second stream needs to be set to ‘subStream’ (without the quotes).
Axis
For Axis cameras the ‘Stream Profile’ depends on which stream needs to be used by VDG Sense. Axis offers several pre-configured streams with the name ‘Mobile’ and ‘Balanced’, but new stream profiles can be added. The names of the stream profiles can be found in the webpage of the camera.
ONVIF
To use dual streaming with camera which are configured as ONVIF device in VDG Sense, the name of the stream profile is unknown. Camera suppliers use unique names for the available streams. To determine the name of the second stream a program called ‘Onvif Device Manager’ is needed and can be downloaded by following this link.
The Onvif Device Manager is able to find all ONVIF compliant cameras in the local network. Follow this procedure to find the name of the ‘Stream Profile’:
Type in the user credentials in the upper left corner of the window
Find and select the correct camera
Click on ‘Profiles’ in the configuration pane, the available profiles appear in the list on the left side
Use the name of the second (or third/fourth if applicable) in the ‘Stream Profile’ setting of the device in VDG Sense.