How to calculate video retention time for Endura NSM5200 Recording Pool?

Issue

How to calculate video retention time for Endura NSM5200 Recording Pool?

Product Line

Pelco Video Management

Environment

  • Endura NSM5200 versions 2.3.1 or greater.

Cause

No software application exists to calculate Endura NSM5200 video retention time (hours/days).

Resolution

note: For Support Assistance with Pre-Sales Endura Storage Calculations, contact Pelco Large Sales Team @ largesystems@pelco.com.

Getting Started
note: The instructions in this article also provide Example Calculations using a fictitious NSM Recording Pool containing two model NSM5200-24-US units, which allows for 17.75TB (TeraBytes) of Usable Storage each, giving us a total of 35.5TB (17.75TB * 2).

  1. Reference Lessons Learned Article LL#12660 to see the total Usable Storage available for each NSM5200 Recorder Model Number, then decide which will be used for a Storage Calculation.
    note: For existing equipment, model number can be found on the frontpanel label, or from the original Purchase Order.
     
  2. Follow the below Example Storage Calculation, replacing the bolded/colored values as appropriate for your calculation.

 

SECTION 1: Existing Installations
For existing NSM5200's already installed in the field, we can perform a calculation using the total incoming Pool bitrate, as seen from the NSM5200 Recording Pool Manager Webui > Pools tab...
(see NSM5200 Web Configuration Manual, Page 11, Figure 4)

  1. First we take our Pool bitrate and multiply that by 60 (seconds in a minute), then again multiple by 60 (minutes in an hour), and finally by 24 (hours in a day), which gives us our Megabits per day (Mb/day)...
    Example Result = < 111 * 60 * 60 * 24 = 9590400 Mb/day >
     
  2. We then convert our Mb/day to GigaBytes per day (GB/day)...
    Example Result = < 9590400 / 8192 = 1170 GB/day  >

    note: There is a math shortcut which can be used to quickly get through steps 1 and 2.
    This shortcut is the number 10.546875, which is the pre-calculated GB/day for a 1 Mbps Video Stream.
    Notice what happens if we take our original Incoming Pool Bitrate (111) and multiply it by this number...
    Example Result = < 111 * 10.546875 = 1170 GB/day >
     
  3. Next, we convert our GB/day to TeraBytes per day (TB/day)...
    1170 / 1024 = 1.142578 TB/day >
     
  4. Finally, we divide our Usable Storage (from the "Getting Started" section at the beginning of this Article) by our TB/day...
    35.5 / 1.142578 31.07 >, which tells us our Example NSM Recording Pool will achieve 31 Days of Video Storage Retention.




SECTION 2: Presales calculation
First we need to determine the total amount of bandwidth - in Megabits per seconds - that all cameras assigned to the NSM5200 Recording Pool will be generating, otherwise known as the Pool bitrate.

!! Choose to follow either  a  or  b  below !!

a. For Existing Equipment Storage Calculations (where all cameras are already assigned and recording to the Pool), this is easily achieved using an Internet Browser* by visiting the IP Address of the NSM5200 Pool Manager, logging in (default password is admin), and noting the Pool bitrate value shown in the NSM Pool tab...
< Example Pool bitrate 111 Mbps (Megabits per second) >

note: Endura Utilities right-click > Open Web Interface dialog option can be used to quickly open the NSM5200 WebUI in your default Internet Browser.
*Pelco recommends Google Chrome for Endura 2.x and higher devices.

!! To continue for Existing Equipment Storage Calculations, skip past b and proceed directly to SECTION 2 further down this article !!

----

b. For Pre-Sales Storage Calculations (where cameras and/or recorders have not been obtained or are not yet operational), accurately determining Pool bitrate can only be achieved by learning the bitrate that each Camera or Encoder Video Stream will be configured for, and then adding and multiplying as needed. These values are user-configurable on a per Camera/Encoder basis.

Choose only one of these three options:

Option 1
To obtain assistance on a Pre-Sales Endura Storage Calculation, contact the Pelco Large Sales Team at largesystems@pelco.com.

or...


Option 2
To assume use of the generic "High Profile" Video Stream Preset, and thereby provide a Ball Park Pre-Sales Storage Estimation (no longer a calculation), access each of the Product Specification Sheets for the Cameras/Encoders to be used in the Estimation; 
For Pelco Cameras/Encoders, start here and then navigate to the appropriate Product Landing page, then select the Downloads tab to locate and view the Specification Sheet. The bitrate for the recommended "High" Profile will be shown in a table, as seen here...

note: Image taken from the Spectra HD Series IP Dome System Specification Sheet.

Once the Bit Rate for each of the Cameras has been determined, simply add each of these numbers, and then convert Kilobits to Megabits and the result is the Pool bitrate; Proceed to SECTION 2.

or...

Option 3
To Learn about the variables involved, so that you can deliver an accurate Pre-Sales Storage Calculation, read on... 

To determine the required bitrate each camera will need to send to the NSM Recording Pool, we must know the site requirements (if any) for resolution and frame rate, Image Quality, as well as determine the real-life content of each of the scenes being viewed (aka Scene Complexity*).
*Scene Complexity can be described as the amount of variance of color and detail in a given real-life scene, and will determine how well a Video Compression Algorithm (H264 for current generation Sarix Cameras/Encoders) will be able to compress an image without significant loss of Image Quality.

For example, a camera pointed at a close-quarters, indoor scene of a plain white-walled, brown-carpeted hallway, with sufficient lighting (but not with fluorescent lighting), which also has no complex shadows, and no nearby windows (doesn't allow too much sunlight or cloud shading to enter the scene), is considered to be a Low Scene Complexity, and as such the Image Quality that the H264 Compression Standard can produces at a given resolution/framerate/bitrate (even a very low bitrate) will likely be interpreted as "great" or "good" by human eyes.

If that same camera were physically relocated to an area of the facility with a High Scene Complexity (without adjusting any configuration settings), such as a high-ceiling overlooking a factory floor, with a vast array of colors, objects, shadows, and lighting, the resulting Image Quality would likely be interpreted as "poor" or "washed out" or "pixelated" or "blurry".

To further explain this, let's look at some screenshots taken from a High Definition Sarix model IX30DN Cameras' Web User Interface:

Here are the available Preset Video Stream Profiles available for IX30DN running firmware revision 1.9.2.2...
 figure 1.

note: The High/Medium/Low Preset values are presets provided by Pelco, and are meant to deliver acceptable Image Quality in most scenes. These preset values may vary from camera-model to camera-model, and from firmware-revision to firmware revision. There exists no authoritive listing of these values across all camera models or firmware revisions, but the "High" values for each series are listed within Product Specification Sheets found on Pelco.com.

Next lets look at the Custom Video Stream Configuration page for this same IX30DN...
 figure 2.


Note that figure 2 shows that the Bit Rate (kbit/sec) has been user-configured to 3,000 (aka 2.93Mb/sec). This represents the maximum bitrate the Camera will be allowed to transmit to the network (to our NSM5200 Recording Pool in this case), but this does not mean that the H264 Compression Standard will need to generate this much bandwidth, as only the combination of Scene Complexity, Resolution, and Image Rate will determine that.

Performing a site survey at a customer facility - with a Camera inhand to test various combinations of settings while pointed at various real-life scenes at the facility - will allow for determination of the lowest possible bitrate setting - for each Camera/Scene - that still results in "Good" Image Quality, thus maximizing the Days of Video Storage possible on the NSM5200 Recording Pool.

Once the Bit Rate for each of the Cameras has been determined, simply add each of these numbers, and then convert Kilobits to Megabits and the result is the Pool bitrate, refer to SECTION 1 to perform calculation.

 

RELATED ARTICLES:

  • LL#9443 - "What is the maximum number of cameras one Endura NSM5200 storage pool can record?"