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.
Gain Control / AGC for Video Surveillance Guide
Published Apr 23, 2015 04:00 AM
**** ******* ** * ********, ****** often **********, ****** ** *** ***** surveillance *****. ** ** ********* **** noticed **** *** ******** **** ********* of ********** **** ****** *** ****, namely ***** / **** ** ******. The ******* *****, **** *** ** our ******* *** *****, ** * prime ******* ** **** *******:
*******, *** ***** ** * ******* and ******* *** ***** **** ** remove **. **** ****** ********* ********* about *** ** *** **** ******* effectively.
** *** ************ ***** *****, ** provide * ****-**** ************* ** **** control:
** ***** ****, ** ********* * series ** *********** ** * ******* of ******. *** **** *****, ** captured *****, ****** *** ********* ***********. Here *** *** ****** ** ******:
- ***** *** ***** **** .* *** (Dark)
- ***** *** ***** **** ** *** (Low *****)
- ***** **** * *** (********** ****)
- ***** **** *** *** (*******)
*** ******* *** **** ****** * HD ******* **** ********, **** *** Bosch ** *** * ***** ** performances.
****** *** *** *******, ** ***** our ******* *** ****** *** ********* key *********:
- *** *********** **** ***** ******* **** with ********* **** ******* ********?
- ****** *** *** **** *******?
- **** ** *** ***** **** ******* settings ** ***?
- **** ************ ****** *** **** ** using **** *******?
- *** ** ************* ******** ** **** control ******?
- *** **** **** ******* ****** ******* Black & ***** *** ***** *****?
- **** ** *** ********* ****** ** different **** ******* ********? **** ****** does ***** ****** **** ** ********* impact?
- **** ****** ** *** *** *** streaming ***** **** ** ***** **** control?
- **** ****** **** ******* ***** ********* (include ** *** ** ***) ****?
Key ********
***'* ***** **** *** *** ******** of *** *****:
- 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 ********** *********** ***** **** ********* **** ********* *** ** **********, surveillance ****** ************* **** ** *** massive ******* ** **** *******. **** is ********* ******* ****** **** **********, it ** **** **** ** ******* scene ******** ** ************.
- 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 ******* *** ****.
***** ** * ***** **** ***** and ******** *** *** ******** **** references ** *** **** ***** *** images:
Configuring *** ********** ****
**** ** ********* ********** ** *** modes:
- ******:*** *******, ****, ******, *** - this ** * ****** ******* *******.
- **:*** *******, ***, ****, ****, ***. A **** **** *******, *** ***** tends ** ** **** *** (***) to **** ** ****** (**** **********).
**** ** ********** ********* ** *** of ***** **********:
- ****:** *******, **** ******* ************* ********* what ***** **** ****** **.
- *****:** ** ***********, * **** *** lock **** ** * ******** ***** (e.g., ****** * **). **** *** be ********* - ** *** ** this ** *** *** * ***** (like ***) *** *** ***** ******* even ********** **** (*** * ***), the ***** ******* ** ***** ** be ***** ****. ** *** ***** hand, ** *** *** ** ** a **** ***** (*** ** ***) and *** ***** ******* ******, *** image **** ** ********* ** ***** grain / *****.
- ***:**** ******* ***** *** ***** ** cap *** ******* **** *** ****** can ******. **** ****** *** ****** the ******** ** ********* *** **** but ****** ** **** ***** *** high *** ** *****'* **********. **** can ** ****** *** ******** **** visual ***** *** ******** ********* ******. However, ** ******, **** ** **** such **** **** **** *** ***** darker **** ******** **** *** ****.
*** ***** ***** ******** ************** ** how ** *** *** ******** **** using **** *** ***** ******* ** an *******:
Gain *** ********** ****** *************
******, **** ** * ************* **** the **** **** ****** (*.*., **** or ****), ** **** *** **** they *** *** '****' ** ******* the '****' *** ***** ***********. *** they *** **** / ******* ***** can ****** ****.
Gain *** ***** *** ***** ***********
*** *** ** ***** ** ************* marketing ***** *** ***** ***********, **** names **** ***********, ************, *******, ***********, etc. *** ** ***** *** ***** advanced ***** ** **** ******* ** improve *** ***** ***** *******. *******, like '***********' **** *******, **** **** to ******** ********* *********** ******* (****** by *** **** ****** ********* ** the***** ********* ************** ***). ***** *** ***** **** not, *******, ******* ** *** ******* imagers. *** ******* ************* ***** **** advanced **** ******* / ***** **********.
**** *** *** *** ***** *** they ****** ** ******** **********. *** can ****** *** *****, *.*.,***** *** ***** ** ********** ** Shootout*** ********** ****** ******* ** *** low-light ***********.
Varying **** ******* **************
** *** * ***** ** *** gain ******* ******* ***** *******, *** below *********** **** *** **** ***** with *** **** ******** **** ********* gain ******. *** *** ***** *** the ******* ****** ** **** **** each ********** ***** ** * ***** gain *****. **** * ****:
** *** ***** *****, ****** ****** would ***** **** *** *** ***** is *** ****. **** **** **** scene, **** **** ******* ******** ** make ******** ***. ******, **** **** 3dB ** ****, *** ***** ** pitch *****.
***'* ******** ** ******* ***** ***** with *** *** ****** ** *****. Take * ****:
***** ** *** ***** ** ******? This *** ** ********* **** **** complex **** *** ***** ***** **** sub * *** ********. ** **** scene, **** ** ***, *** ***** with ******* **** ** ******** **** and ******* **** * *** ** visual *****. *** ****** ******** **** better **** **** ****, ****** *** could ****** ***** ** *** *** gain ****** **** ****. ** * point ** *********, ** ******** **** camera's ********* **** ******* *** **** scene ** ** ***** * ** 9 **.
Color **** - **** ******
*** **** ********* **** **** ******** occurs **** ***** ****. *** *** difference, ** *** ********** ***** ***** is **** **** *****, **** ** needed **** **** ** ****** ***** levels. ** *******, ** * ***, all * ******* ************* ******** ***** gain ******* ** ******* ******. *** can *** **** **** *** ***** visible ***** ****** **** *****.
** ********, **** **** ********, *** images *** ************* ****** *** *** colors *** **** ******* (*****), ******* (Avigilon) ** ******* (** ** *** case **** *** **** ******).
Gain's ****** ** *********
*** ** *** **** *** ***** problems ** *** ***** ************ ** increased ********* ***********. ******* *** **** interesting ******* ** **** **** ** the ****** *********** ** **** ****** and *********, ********** ** *** **** of *** ****** ** *** ***** level ** *** *****.
***** ** * ***** **** ******* the ************. *** ******* *** ***** on .* *** *&* **** *** Axis ****** *** **** ******* *** displayed **** ****** ***** ******, ***** mode *** *** ******** ******.
*** ********* ******* ******* ************ ***** as **** ****** ********. ** **** noticed **** ******* **** **** **** noise *** **** **** ********* *********** in *** *****. **** ***** ** be ** ******* ** ************ ******** aggressive ******** *** ********* **** *******.
***** ** ****, ** ********* *** check **** *** ***** ********* ***********. If ** ** ***** ****, *** if * **** ******* *** ****** and *** ******** ** **** *** manufacturer's ******* *******.
*** ***** ****** ** ** ******. *** ***** ***** ***** *** test ******* ** ****** * ***** with ******* **** *** ******** *** bandwidth ** * **/*. *** ******* image ******* ** *********** ********* *** at * ******** ** *** *********.
Gain ****** ****** *******
*******, **** ** * ******* ********** of **** ****** ***** ******, **** settings *** ******* ******. **** * look *** ******* *** *********** ********. Perhaps *** **** *********** ******* ** saw **** *** **** **** ****** light (*** *** ** *** ****** of *** **********), *** ******** ******* to ******* *** ******** ***** *******. However, **** *** ****, ********'* ***** essentially **********.
Digital ***** ********* *** ****
** ******* *** ****** * ********** to ****** *** ***** ********* ** high **** ******, ***** ** ******* Noise ********* (***).
*** **** ** ****** ******* ***** by ********** ********** ****** (* ***********) or ****** * ****** ** ****** (3 ***********) ** ******** ***** ******* in ***** ** ********* **** ** and ** *** *****. ** ******** overall ***** ** *** *****, ********* requirements *** **** *******, ********* ************.
*** *******, ****** * ****** ** cameras **** ** *** ********* **. low ***** *** *** *****, ******** increased ** ****** *** **** *** to ***** ******* ***** *** (** average ** ** **/* **. ~*.* Mb/s). ******* *** **, ***** ****** dropped ** ~** (~*.** **. ~*.* Mb/s), ***** ***********, *** **** ******** versus *** ***** ***.
*******, ***** ****** ** ******* *** to ***** *** **** ******* ***** reduction, ** **** ****** *** ****** blur ** ****** *******, ******* ** appearance ** **** *******.
*** **** *******, *** ********* ******* ***** ********* *************** ********* **. *** *****.
Quiz ******** ** *** / ****
Comments (13)
JH
John Honovich
Apr 23, 2015
Jon Dillabaugh
Apr 23, 2015U
Undisclosed #1
Apr 23, 2015Interestingly 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?
U
Undisclosed #1
Apr 23, 2015Does 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?
UI
Undisclosed Integrator #2
May 11, 2015After 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.
Ethan Ace
May 13, 2015AGC 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.
Christophe Bonavia
Jul 20, 2017This link could not be found - 'commercial videography where gain control'
JH
John Honovich
Jul 20, 2017Christophe, 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.
UE
Undisclosed End User #3
May 09, 2018Good writeup
UE
Undisclosed End User #3
May 09, 2018Good pictures to show the differentiation.
CL
Chin Liang Benjamin Lee
May 19, 2018Interesting to know the table comparison between different camera vendors on the bit rates with DNR feature on and off...
U
Undisclosed #4
Nov 19, 2018Getting better understanding in the relationship between bandwidth and gain.
AS
Amitkumar Sirjusingh
Dec 29, 2020A comprehensive overview of Gain control and its relationship to lighting conditions as well as the impact on bandwidth.