Gain Control / AGC for Video Surveillance Guide

By IPVM Team, Published on Apr 23, 2015

Gain control is a critical, though often overlooked, factor in low light surveillance video. It is generally only noticed when the negative side effective of aggressive gain levels are seen, namely noise / snow on screen. The picture below, from one of our parking lot tests, is a prime example of this problem:

Clearly, the noise is a problem and ideally you would want to remove it. This raises important questions about how to use gain control effectively.

In the introductory video below, we provide a real-time demonstration of gain control:

To learn more, we conducted a series of experiments in a variety of scenes. For each scene, we captured video, images and bandwidth consumption. Here are the scenes we tested:

  • Black and White Mode .5 Lux (Dark)
  • Black and White Mode 20 lux (Low Light)
  • Color Mode 4 Lux (Moderately Dark)
  • Color Mode 300 Lux (Daytime)

Our testing was done across 3 HD cameras from Avigilon, Axis and Bosch to see a range of performances.

Inside the Pro section, we share our results and answer the following key questions:

  • How significant does image quality vary with different gain control settings?
  • Should you use gain control?
  • What is the right gain control settings to use?
  • What alternatives should you seek to using gain control?
  • How do manufacturers approach to gain control differ?
  • How does gain control differ between Black & White and Color modes?
  • What is the bandwidth impact of different gain control settings? What impact does light levels have on bandwidth impact?
  • What impact do VBR and CBR streaming modes have on using gain control?
  • What impact does digital noise reduction (include 2D and 3D DBR) have?

Key ********

***'* ***** **** *** key ******** ** *** tests:

  • Gain ******* **** *********: In almost any night time scenes, without gain control, surveillance video would be very dark and almost practically useless. While gain control is generally ignored, its role is critical. In low light conditions, trying to turn it off to remove the grain/noise will only result in far worse video quality.
  • Gain ******* ** *********: As the name states, Automatic Gain Control, is automatically controlled by almost every camera. While it can produce lots of noise, disabling it generally will make things even worse.
  • Aggressive ***: Unlike in ********** *********** ***** **** control** **** ********* *** in **********, ************ ****** manufacturers **** ** *** massive ******* ** **** control. **** ** ********* because ****** **** **********, it ** **** **** to ******* ***** ******** in ************.
  • Adjusting **** *******: If you want to minimize the bandwidth impact and visual noise inherent in gain control, the two gain adjustments possible are (1) fixing the gain or (2) capping the gain. The former is dangerous unless you can guarantee constant lighting. The latter, assigning a cap, can be useful.
  • Gain *** *&* *** *****: Both B&W and Color modes use gain and display similar characteristics - bandwidth spikes, visual noise, etc. The big difference is that cameras activate gain at much higher light levels for color than in black & white modes (color at ~50 lux, b&w at ~20 lux).
  • Gain *** ********* ********* ******* **********: As gain increases, bandwidth increases as well in a hockey stick curve. Interestingly, this appears to occur regardless of the light level or mode used.
  • Use ***: Since bandwidth is nearly guaranteed to spike as gain increases, we strongly recommend setting a ******* *** ****.

***** ** * ***** that ***** *** ******** our *** ******** **** references ** *** **** video *** ******:

Configuring *** ********** ****

**** ** ********* ********** by *** *****:

  • ******:*** *******, ****, ******, low - **** ** a ****** ******* *******.
  • **:*** *******, ***, ****, 30dB, ***. * **** gain *******, *** ***** tends ** ** **** 0dB (***) ** **** or ****** (**** **********).

**** ** ********** ********* in *** ** ***** approaches:

  • ****:** *******, **** ******* automatically ********* **** ***** gain ****** **.
  • *****:** ** ***********, * user *** **** **** to * ******** ***** (e.g., ****** * **). This *** ** ********* - ** *** ** this ** *** *** a ***** (**** ***) and *** ***** ******* even ********** **** (*** 5 ***), *** ***** quality ** ***** ** be ***** ****. ** the ***** ****, ** you *** ** ** a **** ***** (*** 27 ***) *** *** scene ******* ******, *** image **** ** ********* by ***** ***** / noise.
  • ***:**** ******* ***** *** admin ** *** *** maximum **** *** ****** can ******. **** ****** the ****** *** ******** to ********* *** **** but ****** ** **** going *** **** *** an *****'* **********. **** can ** ****** *** reducing **** ****** ***** and ******** ********* ******. However, ** ******, **** in **** **** **** will **** *** ***** darker **** ******** **** max ****.

*** ***** ***** ******** demonstrations ** *** ** use *** ******** **** using **** *** ***** cameras ** ** *******:

Gain *** ********** ****** *************

******, **** ** * manufacturers **** *** **** gain ****** (*.*., **** or ****), ** **** not **** **** *** the '****' ** ******* the '****' *** ***** performance. *** **** *** gain / ******* ***** can ****** ****.

Gain *** ***** *** ***** ***********

*** *** ** ***** of ************* ********* ***** low ***** ***********, **** names **** ***********, ************, Stellar, ***********, ***. *** of ***** *** ***** advanced ***** ** **** control ** ******* *** light ***** *******. *******, like '***********' **** *******, they **** ** ******** bandwidth *********** ******* (****** by *** **** ****** depending ** ******** ********* ************** ***). ***** *** Light **** ***, *******, require ** *** ******* imagers. *** ******* ************* comes **** ******** **** control / ***** **********.

**** *** *** *** equal *** **** ****** be ******** **********. *** can ****** *** *****, e.g.,***** *** ***** ** Integrated ** *********** ********** ****** ******* to *** ***-***** ***********.

Varying **** ******* **************

** *** * ***** of *** **** ******* overall ***** *******, *** below *********** **** *** same ***** **** *** same ******** **** ********* gain ******. *** *** image *** *** ******* amount ** **** **** each ********** ***** ** a ***** **** *****. Take * ****:

** *** ***** *****, almost ****** ***** ***** that *** *** ***** is *** ****. **** this **** *****, **** gain ******* ******** ** make ******** ***. ******, even **** *** ** gain, *** ***** ** pitch *****.

***'* ******** ** ******* slide ***** **** *** the ****** ** *****. Take * ****:

***** ** *** ***** is ******? **** *** is ********* **** **** complex **** *** ***** slide **** *** * lux ********. ** **** scene, **** ** ***, the ***** **** ******* gain ** ******** **** and ******* **** * lot ** ****** *****. The ****** ******** **** better **** **** ****, though *** ***** ****** which ** *** *** gain ****** **** ****. As * ***** ** reference, ** ******** **** camera's ********* **** ******* for **** ***** ** be ***** * ** 9 **.

Color **** - **** ******

*** **** ********* **** gain ******** ****** **** color ****. *** *** difference, ** *** ********** below ***** ** **** with *****, **** ** needed **** **** ** higher ***** ******. ** default, ** * ***, all * ******* ************* adjusted ***** **** ******* to ******* ******. *** can *** **** **** the ***** ******* ***** across **** *****.

color mode-gain max vs disabled 4 lux

** ********, **** **** disabled, *** ****** *** significantly ****** *** *** colors *** **** ******* (Bosch), ******* (********) ** altered (** ** *** case **** *** **** camera).

Gain's ****** ** *********

*** ** *** **** oft ***** ******** ** low ***** ************ ** increased ********* ***********. ******* the **** *********** ******* of **** **** ** the ****** *********** ** gain ****** *** *********, regardless ** *** **** of *** ****** ** the ***** ***** ** the *****.

***** ** * ***** that ******* *** ************. The ******* *** ***** on .* *** *&* mode *** **** ****** the **** ******* *** displayed **** ****** ***** levels, ***** **** *** the ******** ******.

*** ********* ******* ******* increasingly ***** ** **** levels ********. ** **** noticed **** ******* **** very **** ***** *** very **** ********* *********** in *** *****. **** looks ** ** ** outcome ** ************ ******** aggressive ******** *** ********* gain *******.

***** ** ****, ** recommend *** ***** **** low ***** ********* ***********. If ** ** ***** high, *** ** * gain ******* *** ****** and *** ******** ** from *** ************'* ******* maximum.

*** ***** ****** ** to ******. *** ***** ***** shows *** **** ******* of ****** * ***** with ******* **** *** limiting *** ********* ** 1 **/*. *** ******* image ******* ** *********** unchanged *** ** * fraction ** *** *********.

bandwidth impact at max gain

Gain ****** ****** *******

*******, **** ** * summary ********** ** **** across ***** ******, **** settings *** ******* ******. Take * **** *** compare *** *********** ********. Perhaps *** **** *********** element ** *** **** was **** **** ****** light (*** *** ** the ****** ** *** comparison), *** ******** ******* to ******* *** ******** image *******. *******, **** low ****, ********'* ***** essentially **********.

impact of varying lux and gain across cameras

Digital ***** ********* *** ****

** ******* *** ****** a ********** ** ****** the ***** ********* ** high **** ******, ***** as ******* ***** ********* (DNR).

*** **** ** ****** digital ***** ** ********** individual ****** (* ***********) or ****** * ****** of ****** (* ***********) to ******** ***** ******* in ***** ** ********* what ** *** ** not *****. ** ******** overall ***** ** *** image, ********* ************ *** also *******, ********* ************.

*** *******, ****** * sample ** ******* **** in *** ********* **. low ***** *** *** tests, ******** ********* ** nearly *** **** *** to ***** ******* ***** DNR (** ******* ** 10 **/* **. ~*.* Mb/s). ******* *** **, these ****** ******* ** ~3x (~*.** **. ~*.* Mb/s), ***** ***********, *** much ******** ****** *** using ***.

*******, ***** ****** ** careful *** ** ***** too **** ******* ***** reduction, ** **** ****** can ****** **** ** moving *******, ******* ** appearance ** **** *******.

*** **** *******, *** our****** ******* ***** ********* Guide********** ********* **. *** Light.

Quiz ******** ** *** / ****

**** *** *** / Gain **** ***.

Comments (12)

Note: The first version of this post was written in 2011. We have updated it significantly adding in sections about 'super low light' and digital noise reduction, two key technological advances that have occurred in the past 4 years.

I wondered where the intro splash for the video was...?

Interestingly Axis eliminates the need for DNR thru meticulous cooling:

...digital noise reduction is widely used in image processing techniques to eliminate visible noise. The purpose is to improve image quality and lower the bandwidth used for encoding...

Axis has chosen a different approach. The image sensor is meticulously cooled and in doing the need for digital noise reduction is eliminate. The advantage of this system is that it does not need any computing power or extra equipment, such as fans. Instead, it removes the noise ‘from the source’. Beyond Standards - Axis 2015

IMHO, Axis images are typically sharp (except for 4K) but gritty, this might explain why.

Since relying on a mfr's SNR is, at best, useful as a relative measure within a mfr, what is the best way to measure/compare noise in general?

Does anyone know the reason the 20lux image gets darker from the 18db to the 27db? Is the iris or shutter going too far in trying to compensate for the excessive gain?

After a quick review I was a little surprised there was no mention made of what the effect of AGC noise can have on motion detection recording. The turning OFF of lights in a room, in an effort by customers to save power costs and be more 'green'', will almost without doubt cause unwanted, false triggered, recording(s) of non-occupied areas, thus impacting hard drive space and calculated retention of video data.

AGC noise can be a problem, but we didn't find it to be major in our tests. In fact, of the seven manufacturers we tested (Avigilon, Axis, Bosch, Sony, and Dahua, Hikvision, Samsung), none of them frequently triggered based on noise in dark scenes. Opening or closing a door or someone walking by a window in a lit hallway triggered motion, yes, but pure noise, no.

Compared to years ago, when we originally tested VMD, this is much improved.

Also, with integrated IR becoming more and more popular, lower gain levels and less noise are becoming more common, since the illuminator adds usable light to the scene.

I'm not saying it can't happen, and I'm sure it does, but at least for cameras I see lately, the problem of all night recording due to noise is at least reduced.

This link could not be found -  'commercial videography where gain control'

 

 

Christophe, thanks. It looks like in the past half year that the site linked to was shut down or bought. Here is a link to the archived 'commercial videography where gain control' article.

Good writeup

Good pictures to show the differentiation.

Interesting to know the table comparison between different camera vendors on the bit rates with DNR feature on and off...

Getting better understanding in the relationship between bandwidth and gain.

Read this IPVM report for free.

This article is part of IPVM's 6,604 reports, 890 tests and is only available to members. To get a one-time preview of our work, enter your work email to access the full article.

Already a member? Login here | Join now

Related Reports

Use Access Control Logs To Constrain Coronavirus on Apr 09, 2020
Access control users have included capabilities that are not commonly used...
Access Control Levels and Schedules Tutorial on Sep 29, 2020
Configuring access levels and setting up schedules is central to maintaining...
FLIR A Series Temperature Screening Cameras Tested on Jun 04, 2020
FLIR is one of the biggest names in thermal and one of the most conservative....
Verkada Access Control Tested on Sep 09, 2020
Verkada raised $80 million earlier in 2020, expanding from video into access...
Drain Wire For Access Control Reader Tutorial on Sep 23, 2020
An easy-to-miss cabling specification plays a key role in access control, yet...
Exit Devices For Access Control Tutorial on Aug 25, 2020
Exit Devices, also called 'Panic Bars' or 'Crash Bars' are required by safety...
Face Masks Increase Face Recognition Errors Says NIST on Aug 04, 2020
COVID-19 has led to widespread facemask use, which as IPVM testing has shown...
Video Surveillance History on May 06, 2020
The video surveillance market has changed significantly since 2000, going...
Forced Door Alarms For Access Control Tutorial on Aug 17, 2020
One of the most important access control alarms is also often ignored....
Biggest Problems Selling Access Control 2020 on Oct 29, 2020
Access control can cause integrators big headaches. What practical issues do...
Remote Network Access for Video Surveillance Guide on Jul 27, 2020
Remotely accessing surveillance systems is key in 2020, with more and more...
Low Voltage Nation Wants to "Help You Carve Out A Fulfilling Career" Interviewed on Jul 06, 2020
It is difficult to make your way in this industry as there is little formal...
Gait Recognition Examined on Sep 14, 2020
Facial recognition faces increasing ethical and political criticisms while...
FLIR Screen-EST Screening Software Tested on Jun 30, 2020
In our FLIR A Series Test, the cameras' biggest drawback was their lack of...
Top Video Surveillance Service Call Problems 2020 on Oct 23, 2020
3 primary and 4 secondary issues stood out as causing the most problems when...

Recent Reports

Motorola Solutions Total Revenue Down, Video Revenue Up on Oct 30, 2020
Motorola Solutions' total revenue is down, but video (both fixed and...
Recruiters Show 2020 On-Demand Recordings on Oct 30, 2020
Recordings from the 12 recruiter presentations are now available...
Consultants Show 2020 On-Demand Recording on Oct 29, 2020
Recordings from the consultant show are available on-demand at the end of...
Hikvision AcuSense G2 Camera Test on Oct 29, 2020
Hikvision has released their next generation of AcuSense analytic cameras...
Biggest Problems Selling Access Control 2020 on Oct 29, 2020
Access control can cause integrators big headaches. What practical issues do...
Taiwan Geovision AI Analytics and NDAA Examined on Oct 29, 2020
Taiwan manufacturer Geovision's revenue has been falling for years. However,...
Bedside Cough and Sneeze Detector (Sound Intelligence and CLB) on Oct 28, 2020
Coronavirus has increased interest in detecting symptoms such as fever and...
Fever Tablet Thermal Sensors Examined (Melexis) on Oct 28, 2020
Fever tablet suppliers heavily rely on the accuracy and specs of...
Verkada Fires 3 on Oct 28, 2020
Verkada has fired three employees over an incident where female colleagues...
Eagle Eye Networks Raises $40 Million on Oct 27, 2020
Eagle Eye has raised $40 million aiming to "reinvent video...
Hikvision Q3 2020 Global Revenue Rises, US Revenue Falls on Oct 27, 2020
While Hikvision's global revenue rises driven by domestic recovery, its US...
VICE Investigates Verkada's Harassing "RawVerkadawgz" on Oct 26, 2020
This month, IPVM investigated Verkada's sexism, discrimination, and cultural...
Six Flags' FDA Violating Outdoor Dahua Fever Cameras on Oct 26, 2020
As Six Flags scrambled to reopen parks amid plummeting revenues caused by the...
ISC Brasil Digital Experience 2020 Report on Oct 23, 2020
ISC Brasil 2020 rebranded itself to ISC Digital Experience and, like its...
Top Video Surveillance Service Call Problems 2020 on Oct 23, 2020
3 primary and 4 secondary issues stood out as causing the most problems when...