Dahua settings

[cam26]

Hi all,

Three settings I'm having trouble finding the details on..

1) Auto Iris- What exactly does this setting do? And using manual shutter/gain, should this be on or off?

2) Exposure comp- What exactly does this setting do? I understand that it brightens/darkens the image, however what are the cons to using this? Does it increase noise or motion blur when set higher/brighter? Once again, I use manual shutter/gain.

3) 3D/2D NR- What are the differences and pros/cons for each, especially for 2D NR. What does 3D NR affect that 2D doesn't, and vice versa?

Note* I have looked at Dahua's information on these settings but the explanations are still pretty vague.

 

[cam26]

Anyone have any insight?

 

[wittaj]

See below for setting up the camera.

Exposure comp only works if you are on default settings, which you shouldn't be, so no need to worry about it (well it shouldn't be but some firmware is allowing it, but just leave it at 50).

In most cases it is best to just use auto iris.

You need NR (noise reduction) as these are digital images. In theory 2D is noise reduction for non moving objects and 3D is for moving objects. The reality is they both impact moving objects.

Here is my "standard" post that many use as a start for dialing in day and night:

Every field of view is different, but I have found you need contrast to usually be 6-8 higher than the brightness number at night.

But first, run H264, smart codec off, CBR, and 8192 bitrate to start, along with 15 FPS and 15 i-frame.

We want the ability to freeze frame capture a clean image from the video at night, and that is only done with a shutter of 1/60 or faster. At night, default/auto may be on 1/12s shutter or worse to make the image bright.

In my opinion, shutter (exposure) and gain are the two most important parameters and then base the others off of it. Shutter is more important than FPS. It is the shutter speed that prevents motion blur, not FPS. 15 FPS is more than enough for surveillance cameras as we are not producing Hollywood movies. Match iframes to FPS. 15FPS is all that is usually needed.

Many people do not realize there is manual shutter that lets you adjust shutter and gain and a shutter priority that only lets you adjust shutter speed but not gain. The higher the gain, the bigger the noise and see-through ghosting start to appear because the noise is amplified. Most people select shutter priority and run a faster shutter than they should because it is likely being done at 100 gain, so it is actually defeating their purpose of a faster shutter.

Go into shutter settings and change to manual shutter and start with custom shutter as ms and change to 0-8.3ms and gain 0-50 (night) and 0-4ms exposure and 0-30 gain (day)for starters. Auto could have a shutter speed of 100ms or more with a gain at 100 and shutter priority could result in gain up at 100 which will contribute to significant ghosting and that blinding white you will get from the infrared or white light.

Now what you will notice immediately at night is that your image gets A LOT darker. That faster the shutter, the more light that is needed. But it is a balance. The nice bright night static image results in Casper blur and ghost during motion LOL. What do we want, a nice static image or a clean image when there is motion introduced to the scene?

In the daytime, if it is still too bright, then drop the 4ms down to 3ms then 2ms, etc. You have to play with it for your field of view.

Then at night, if it is too dark, then start adding ms to the time. Go to 10ms, 12ms, etc. until you find what you feel is acceptable as an image. Then have someone walk around and see if you can get a clean shot. Try not to go above 16.67ms (but certainly not above 30ms) as that tends to be the point where blur starts to occur. Conversely, if it is still bright, then drop down in time to get a faster shutter.

You can also adjust brightness and contrast to improve the image.

You can also add some gain to brighten the image - but the higher the gain, the more ghosting you get. Some cameras can go to 70 or so before it is an issue and some can't go over 50.

But adjusting those two settings will have the biggest impact. The next one is noise reduction. Want to keep that as low as possible. Depending on the amount of light you have, you might be able to get down to 40 or so at night (again camera dependent) and 20-30 during the day, but take it as low as you can before it gets too noisy. Again this one is a balance as well. Too smooth and no noise can result in soft images and contribute to blur.

Do not use backlight features until you have exhausted every other parameter setting. And if you do have to use backlight, take it down as low as possible.

After every setting adjustment, have someone walk around outside and see if you can freeze-frame to get a clean image. If not, keep changing until you do. Clean motion pictures are what we are after, not a clean static image.

 

[cam26]

Thank you for the info! Makes sense. Exposure comp seems to brighten the image quite a bit, but I’m not on default settings.

 

[Lincos]

See below for setting up the camera.



But first, run H264, smart codec off, CBR, and 8192 bitrate to start, along with 15 FPS and 15 i-frame.

wittaj, can you please explain why to run H264 instead of H265?

Thanks!

 

[wittaj]

This will explain H264 versus H265 a little better.

H265 in theory provides more storage as it compresses differently, but part of that compression means it macro blocks big areas of the image that it thinks isn't moving. However, it also takes more processing power of the already small CPU in the camera and that can be problematic if someone is maxing out the camera and then it stutters.

In theory it is supposed to need 30% less storage than H264, but most of us have found it isn't that much. My savings were less than few minutes per day. And to my eye and others that I showed clips to and just said do you like video 1 or video 2 better, everyone thought the H264 provided a better image.

The left image is H264, so all the blocks are the same size corresponding to the resolution of the camera. H265 takes areas that it doesn't think has motion and makes them into bigger blocks and in doing so lessens the resolution yet increases the CPU demand to develop these larger blocks.

In theory H265 is supposed to need half the bitrate because of the macroblocking. But if there is a lot of motion in the image, then it becomes a pixelated mess. The only way to get around that is a higher bitrate. But if you need to run the same bitrate for H265 as you do H264, then the storage savings is zero. Storage is computed based on multiplying bitrate, FPS, and resolution.



In my testing I have one camera that sees a parked car in front of my house. H265 sees that the car isn't moving, so it macroblocks the whole car and surrounding area. Then the car owner walked up to the car and got in and the motion is missed because of the macroblock being so large. Or if it catches it, because the bitrate is low, it is a pixelated mess during the critical capture point and by the time H265 adjusts to there is now motion, the ideal capture is missed.

In my case, the car is clear and defined in H264, but is blurry and soft edges in H265.

Digital zooming is never really good, but you stand a better chance with H264 rather than a large macroblocked H265. I can digital zoom on my overview camera and kinda make out the address number of the house across the street with H264, but not a chance with H265 as it macroblocked his whole house.

H265 is one of those theory things that sounds good, but reality use is much different.

As always, YMMV.

 

[Lincos]

Ok, that's clear. Now i can play around with it with a bit more understanding what to expect
Thanks!