ArUco detection on macOS (AVFoundation → OpenCV 4) intermittently returns no markers — sanity check on params/pipeline?

1

ArUco detection on macOS (AVFoundation → OpenCV 4) intermittently returns no markers — sanity check on params/pipeline?

Hi all — I’m running an ArUco detector on macOS using AVFoundation for capture and OpenCV 4 (Homebrew). The pipeline is: capture BGRA CVPixelBuffer → convert to grayscale → cv::aruco::detectMarkers with DICT_4X4_50. Streaming works, but detection is inconsistent (often prints no markers) even with clean, high-contrast tags.

Environment

• macOS: [from sw_vers], Arch: [arm64/x86_64]

• Xcode/Swift: [versions]

• OpenCV: 4.x via Homebrew (prefix: [brew --prefix opencv@4])

• Linking via Package.swift with -I /include/opencv4 and -L /lib

Detector core (simplified)

• Convert BGRA → gray: cv::cvtColor(bgra, gray, cv::COLOR_BGRA2GRAY)

• dict = DICT_4X4_50

• params = DetectorParameters::create() (mostly defaults)

• cv::aruco::detectMarkers(gray, dict, corners, ids, rejected)

What I’ve tried

• Verified dictionary/IDs (0–49), multiple prints/sizes, improved lighting/distance

• Parameter sweeps: adaptiveThreshWinSizeMin/Max/Step, minMarkerPerimeterRate, cornerRefinementMethod (Subpix/None)

• Confirmed pixel format path (BGRA to gray) and tested lower camera presets

What would help

• Recommended starting parameters for DICT_4X4_50 on typical 720p/1080p webcam input

• Common pitfalls in macOS CVPixelBuffer → cv::Mat conversion that affect ArUco

• Quick checks to distinguish parameter issues vs. frame conversion issues

• If you have a known-good minimal config for 4x4_50, I’d love to compare

Artifacts

• I can provide a few PNG frames (pre-detection) where I expect detection but get none, plus logs of ids/rejected count.

Thanks in advance — looking for a sanity check and known-good parameter baselines before I dig deeper.

2

don’t let AI write your question.

post a picture instead. from the camera, where it sees a marker but the code doesn’t detect it.

3

This is the appropriate phrasing for the problem I am having; it is an ArUco dictionary. If I knew I was just going to get hated on, I would not have posted to this forum. You can either address the problems or help others

4

well, that was my offer of help. show me a picture.

you yourself offered that, but seemed to want prompting. you can just post that without prompting. this is now my second prompt.

5

Oh caught me how dare I attempt to save time