Triggering LPR cam with Overview cam issue

[biggen]

For sometime I've been using my overview cam to trigger my LPR cam when cars enter into the overview cam's FOV. It's setup with BI motion detection on the Overview and then under the Trigger tab of the Overview I have "Trigger camera groups" checked with "lprgroup" as the group to trigger. The LPR cam is in the "lprgroup" all by itself. It's a simple setup that works pretty well. But I've noticed after reviewing my footage that I'm missing triggers in my LPR cam that my overview cam has captured. It seems that retriggers are the issue. The inital trigger of the Overview cam immediately triggers the LPR cam (lprgroup) which is correct. However, if the overview cam gets retriggered before breaktime, it never retriggers the LPR cam (lprgroup). So the LPR cam will stop recording. I'll have a stream of cars in the Overview cam that I captured in a single trigger event, but I'll be missing most of them in the LPR trigger of the same even because it stopped recording.

Trigger tabs for both cameras:



LPR Record Tab:



What am I missing in that the overview isn't retriggering the LPR group? I want to make sure those cameras are synced up 100% so the LPR will always record what the overview is recording.

 

[wittaj]

Three thoughts.

One is set up a clone for the overview and make it a smaller End Trigger so that it creates a snapshot for each plate.

Or run continous+triggered on the LPR and thus use substreams and up substream D1 bitrate to 1024 or 2048 and at least have substream video to review later if the overview cam missed the trigger.

How much resolution is really needed for LPR

We have folks come here all the time thinking that more MP is better, whether it be for general purposes or for LPR. Those of us that have been around long enough know that sensor size is more important than MP. Those that have been here awhile know that I share a representative sample of...

ipcamtalk.com

Or what about abandoning the overview trigger and spend time dialing in motion for the LPR camera?

Here is my setup and you can see from the alert images, I am generally getting them with the plate in the center of the frame. In my case, it was draw a zone where I did so that the cars going right to left, I catch the front plate, and cars going left to right, I catch the back plate. It is some trial and error to get the FOV and zone line drawn to where you get them, but you see the idea in how to get it to trigger an alert with the vehicle in the frame. I do zoom in at night as this FOV for nightime was just a little too wide, but it is fine for daytime.

And then if you only wanted to catch vehicles going in one direction, simply add another zone to account for that.

I have the end trigger at 0.1 second so that I get another image if a car comes thru immediately after.

This process also allows for the plate to be in the image for any AI activities. Using an overview camera, it could be hit or miss based on speed of vehicle.

 

[biggen]

Three thoughts.

One is set up a clone for the overview and make it a smaller End Trigger so that it creates a snapshot for each plate.

Or run continous+triggered on the LPR and up the bitrate to 1024 or 2048 and at least have video to review later if the overview cam missed the trigger.

How much resolution is really needed for LPR

We have folks come here all the time thinking that more MP is better, whether it be for general purposes or for LPR. Those of us that have been around long enough know that sensor size is more important than MP. Those that have been here awhile know that I share a representative sample of...

ipcamtalk.com

Or what about abandoning the overview trigger and spend time dialing in motion for the LPR camera?

Here is my setup and you can see from the alert images, I am generally getting them with the plate in the center of the frame. In my case, it was draw a zone where I did so that the cars going right to left, I catch the front plate, and cars going left to right, I catch the back plate. It is some trial and error to get the FOV and zone line drawn to where you get them, but you see the idea in how to get it to trigger an alert with the vehicle in the frame. I do zoom in at night as this FOV for nightime was just a little too wide, but it is fine for daytime.

And then if you only wanted to catch vehicles going in one direction, simply add another zone to account for that.

I have the end trigger at 0.1 second so that I get another image if a car comes thru immediately after.

This process also allows for the plate to be in the image for any AI activities. Using an overview camera, it could be hit or miss based on speed of vehicle.

Thanks for this information. I have my bitrate set quite high at 13000 which is probably overkill on a 2MP Z12. I have noticed though that plates are quite a bit clearer at this bit rate during low light however.

I've played with using motion on the LPR camera in BI and it's not reliable with my FOV for whatever reason. BI will simple "miss" cars moving through the entire zone "A" if I attempt to use the entire FOV as a whole zone as a motion trigger. I've even played with splitting the FOV on the left side to Zone A and the right side to Zone B and setting up a object rule in BI that objects must cross (A-B) and BI will still occasionally miss the motion. I'm guessing it too close of a shot of the road and the vehicle moves too fast through the FOV for BI to reliable call it a motion event? I don't know but motion on the LPR has never been 100% successful.

I've not done a small zone in the middle like your have shown however. Mine was for the entire screen. I'll give that a try and see.

I think I will email Ken and ask why my overview cam re-triggers aren't being sent to the triggered cam group.

 

[wittaj]

I meant the higher bitrate for the substream - run D1 at 1024 or 2048 with cont+triggers so that you keep down storage, but will still have readable video if it didn't trigger.

What FPS are you using?

Early on in my migration from NVR to BI, I noticed the my LPR camera wouldn't trigger in every instance (I knew this because the overview cam triggered and the LPR camera didn't)

So I noticed while watching it live for an extended period that for my license plate camera (which as you know is zoomed in tight to the road to read plates), I watched it not trigger for a big ole yellow school bus, but then trigger for a tiny 2-door car the next minute that was driving slower and then miss the same car coming back 5 minutes later!

For this plate camera, I was obviously running a fast shutter to capture plates, but also had the FPS at 30 FPS thinking that would be better. When I knocked it down to 10 FPS, Blue Iris motion started capturing that bus and other vehicles it was missing. I think the motion algorithm for a tight field of view was having difficulty with the faster FPS as there wasn't as much of a difference comparing frame to frame at 30FPS to 10FPS. A vehicle is in and out of my LPR field of view in under 0.5 seconds and I now get trigger alerts and capture every plate at 8FPS (yes I dropped it even further for longer retention of LPR images).

So if you are running a faster FPS, try dropping it.

 

[biggen]

I meant the higher bitrate for the substream - run D1 at 1024 or 2048 with cont+triggers so that you keep down storage, but will still have readable video if it didn't trigger.

What FPS are you using?

Early on in my migration from NVR to BI, I noticed the my LPR camera wouldn't trigger in every instance (I knew this because the overview cam triggered and the LPR camera didn't)

So I noticed while watching it live for an extended period that for my license plate camera (which as you know is zoomed in tight to the road to read plates), I watched it not trigger for a big ole yellow school bus, but then trigger for a tiny 2-door car the next minute that was driving slower and then miss the same car coming back 5 minutes later!

For this plate camera, I was obviously running a fast shutter to capture plates, but also had the FPS at 30 FPS thinking that would be better. When I knocked it down to 10 FPS, Blue Iris motion started capturing that bus and other vehicles it was missing. I think the motion algorithm for a tight field of view was having difficulty with the faster FPS as there wasn't as much of a difference comparing frame to frame at 30FPS to 10FPS. A vehicle is in and out of my LPR field of view in under 0.5 seconds and I now get trigger alerts and capture every plate at 8FPS (yes I dropped it even further for longer retention of LPR images).

So if you are running a faster FPS, try dropping it.

I didn't even think about how BI uses the substream for motion events and not the main stream! That may be the issue with it missing motion.

Camera is running 20fps. I'll play around with this today as well. Thanks for the ideas!

 

[wittaj]

I think I will email Ken and ask why my overview cam re-triggers aren't being sent to the triggered cam group.

On the alerts screen on the left, how long are your "clips". I think it is capturing it but it all shows as one clip as opposed to each vehicle if a car comes thru during the time that it re-triggers.

In other words, since you are only recording Triggered, if you playback a clip where two cars came thru and it retriggered during the 1st trigger, does the LPR cam capture both cars on video even though it only shows one clip?

If so, that is the way it works for a retrigger is it shows in one "clip" as compared to multiple clips. You would have to set the end break time to a smaller duration to get "clips" for each car.

Like literally I will get two alert image "clips" if someone is riding someones bumper because my break time and max alert duration are less than a second.

 

[biggen]

On the alerts screen on the left, how long are your "clips". I think it is capturing it but it all shows as one clip as opposed to each vehicle if a car comes thru during the time that it re-triggers.

In other words, since you are only recording Triggered, if you playback a clip where two cars came thru and it retriggered during the 1st trigger, does the LPR cam capture both cars on video even though it only shows one clip?

If so, that is the way it works for a retrigger is it shows in one "clip" as compared to multiple clips. You would have to set the end break time to a smaller duration to get "clips" for each car.

Like literally I will get two alert image "clips" if someone is riding someones bumper because my break time and max alert duration are less than a second.

Looking at my clip times I'm seeing that the LPR cam is always triggered/recording for a maximum of 5 seconds which corresponds exactly to my break time for that camera. My overview camera (which is also set to a 5 second break time) has varying lengths of recording time as it is getting retriggered. I would think that all the clips for those two cameras would have identical time lengths if the Overview Cam is feeding the same trigger/re-triggers to the LPR cam.

This is apparent as well if I watch the cams live in UI3. I'll see the orange record outline pop-up around the Overview Cam box and the LPR Cam box at the same time. 5 seconds later, the LPR orange box will drop off while the overview cam will still be highlighted in orange since it's being retriggered.

Yeah, I really think re-trigger rules aren't enforced when secondary camera groups are triggered unless it's an option to enable somewhere and I'm missing it.

 

[biggen]

On the alerts screen on the left, how long are your "clips". I think it is capturing it but it all shows as one clip as opposed to each vehicle if a car comes thru during the time that it re-triggers.

In other words, since you are only recording Triggered, if you playback a clip where two cars came thru and it retriggered during the 1st trigger, does the LPR cam capture both cars on video even though it only shows one clip?

If so, that is the way it works for a retrigger is it shows in one "clip" as compared to multiple clips. You would have to set the end break time to a smaller duration to get "clips" for each car.

Like literally I will get two alert image "clips" if someone is riding someones bumper because my break time and max alert duration are less than a second.

So I went back to two zones in BI (A and B) split half and half vertically and set up an object rule to detect movement from A-B. I then upped the substream to CBR of 1024 and this seems to have solved BI missing motion on that tight FOV at high speeds. This may be the way to go instead of relying on the overview cam. I'm so glad you suggested this as I didn't even think about it!

The real test will be in the evening but so far so good the last 30 minutes or so.