LPC - CBR vs VBR?

E

EssDeeEll

n3wb
Oct 11, 2019
19
3
LONDON
Hi guys, new to the forum but have been lurking for a while.

I'm trying to find information as to what would be better for LPC by way of bit rate - constant or variable?

My setup:

Dahua DH-HDW5232RP-ZE @ 5x zoom located 50 feet diagonally from capture area
Using SmartPSS and basic Dahua NVR

Day settings:

Shutter 1/2000
Gain 0 -25
Auto iris on
3DNR 50
Backlight off
Day/night B/W
50 fps
I-frame 50
H.264H
Smart codec off
1080p
CBR (10240 kb/s)

plateday.jpg


I found that these settings work good for me. Cars come down here at an average 29mph (got this info from a police speed survey I requested) in the day however, this is the UK and the weather changes constantly. One minute it's cloudy, the next blazing sun then heavy rain, snow you name it.... it literally is 10/10 plates legible when it's overcast/sunny, 9/10 with heavy rain.

Looking at the scene there isn't a lot of movement except the cars (870 per day!) and the evergreen bush to the left.

I just wanted to know from those more in the know if I am unnecessarily wasting bandwidth or HDD space with CBR? I automatically assumed that due to the speed of the cars in a smallish capture area the bitrate wouldn't increase in time to be of any use to the plate capture? Is this a logical assumption?

In addition to that I did wonder if masking would help? As in masking of the only constantly moving thing - the bush. Does masking just mask visually, or physically at CCD level? I'm no expert so this might come across as nonsense so please forgive me in advance.

My night settings I seem to be doing okayish.... still messing around. Will post about those once I get a few more nights testing but will say I have an added dilemma of street lights turning off at 1am which makes things difficult.

View attachment 48748

Thanks and look forward to some of your helpful insights.
 
Agree with @usaf_pride you could use more zoom especially with that angle.
(Of course your plates have bigger letters than most here in the US)

I run different profiles say/night. Decreased exposure , more gain, lots of IR

That said, my experience with both Axis and Dahua reading plates CBR is the way to go.
 
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I hear the zoom thing guys, that's at 5x already.

I'm going to be growing a privet hedge along the front so can bury the cam in there eventually. For the moment it has to be on the sofit.

That said, it's actually not terrible still

20191009_210737.jpg

This is my van. No street light, pitch black. Not too shabby.

Thanks for the advice, will keep it CBR - never had an issue with space. I get 5 days continuous from 4 cams.

So do you guys in the states etc have reflective plates like ours in the the UK?
 
Reflective but so many versions colors, and smaller letters, they can be difficult.
 
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bigredfish said:
Reflective but so many versions colors, and smaller letters, they can be difficult.
Click to expand...

I see. Are they predominantly metal or are they plastic laminate? I find the plates here often get water between the perspex and the reflective part which bubbles,, hiding digits. Some are more reflective than others too.

Rear plates are lit too which is a pain. Bright lit is ok (led) but dull lit (incandescent) is worse than not lit at all!

Find myself getting impatient to get home of an evening to review the footage and adjust to get the best of all worlds

Would definitely not want to be an installer for a dedicated system unless I could choose camera location etc
 
So here's a little sample from night time with street lighting....

strip.jpg

Settings:

Anti flicker - outdoor (not sure this has any benefits. Maybe for LED car lights?)
Shutter 1/500
Gain 33
Auto iris off
3DNR 11
Back light - HLC 15
Smart IR off (manual set to 100%)

50 FPS
I-frame interval 50
1080p
CBR
H.264H

Going to wait till 1am and hope for some cars... it get's pretty dead after then.
time line.jpg
 
Good start.

What’s the distance from camera to plate?
 
bigredfish said:
Good start.

What’s the distance from camera to plate?
Click to expand...

I think with hindsight it's more like 25-35 feet or there about. With the optical zoom it looks to be as if the camera was only 15 feet away.

Roll on 1am, 00:25 right now.

I also have a white box van which I purposely park with the back doors facing the capture zone as it seems the reflection of the headlights on the doors bounce back at the correct angle onto the plate. If I move the van it's clear the image quality is ever so slightly less. Can't rely on things like that as I don't always get my spot.
 
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