Korean license plate recognition error

[MARIO SHIN]

Hello.

I am currently developing a program that recognizes Korean vehicle license plates using the Doubango ALPR SDK on a Raspberry Pi 5 board.

I have found an error in the SDK that always misrecognizes certain characters on license plates.

In the attached images, the character “배” in the vehicle license plates is always incorrectly recognized as “바” in the SDK's recognition results.

This issue also occurs consistently in the online demo URL at https://www.doubango.org/webapps/alpr/.  

[Mamadou DIOP]

Hello, 

For South Korea le license plate is pretty complex. It's per category (taxi, construction car, police vehicle...). In the attached image the license correspond to "Delivery Van/Truck: 배" according to wikipedia. If the sdk fails to recognize it this means the training data has zero entry for the character "배". Only way to fix is to re-train with such plates. Unfortunately not planning to do it in the coming months.

You can fix it easily on your side by checking the 2 first digits.:

- 11 to 69: letter is 바

- otherwise: letter is 배

https://en.m.wikipedia.org/wiki/Vehicle_registration_plates_of_South_Korea

Sent from my Galaxy

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[Mamadou DIOP]

On 8/26/2025 1:24 PM, 'Mamadou DIOP' via doubango-ai wrote:

Hello, 

For South Korea le license plate is pretty complex. It's per category (taxi, construction car, police vehicle...). In the attached image the license correspond to "Delivery Van/Truck: 배" according to wikipedia. If the sdk fails to recognize it this means the training data has zero entry for the character "배". Only way to fix is to re-train with such plates. Unfortunately not planning to do it in the coming months.

You can fix it easily on your side by checking the 2 first digits.:

- 11 to 69: letter is 바

- otherwise: letter is 배

https://en.m.wikipedia.org/wiki/Vehicle_registration_plates_of_South_Korea

something like:

if (license_plate.matches(LLNNLNNNN) and license_plate[4]=="바" and int(license_plate[2:3]) > 69) {

    license_plate[4]=배

}

Sent from my Galaxy

-------- Original message --------

From: MARIO SHIN <tru...@gmail.com>

Date: 8/26/25 12:57 (GMT+01:00)

To: doubango-ai <douba...@googlegroups.com>

Subject: Korean license plate recognition error

Hello.

I am currently developing a program that recognizes Korean vehicle license plates using the Doubango ALPR SDK on a Raspberry Pi 5 board.

I have found an error in the SDK that always misrecognizes certain characters on license plates.

In the attached images, the character “배” in the vehicle license plates is always incorrectly recognized as “바” in the SDK's recognition results.

This issue also occurs consistently in the online demo URL at https://www.doubango.org/webapps/alpr/.  


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