Platform Observer (Bus Detection System)

Detects stopped buses at station platforms in real-time using CCTV video streams and dynamically configurable ROIs.
Detection results are written to shared memory for use by other processes (e.g., CGI scripts).

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Key Features

• Dual Video Input Modes

  • Live Mode: Receives real-time frames via shared memory (/busbom_frame)
  • Video File Mode: Reads local .mp4 file for debugging (passed as command-line argument)

• Dynamic ROI Configuration

  • Receives ROI updates via Unix domain socket (/tmp/roi_socket) from external tools like web CGI
  • No restart required to apply new ROI settings

• Multi-threaded Pipeline

  • Independent threads for:
    • Video reading
    • Perspective warping
    • Filtering & masking
    • State analysis

• Robust State Stabilization (Debouncing)

  • Stop condition is confirmed only if the bus is detected continuously for a set duration (e.g., 3 seconds)
  • Up to 5 temporary detection losses (flickers) are tolerated within this window

• Shared Memory Output

  • Final result (StopStatus) is written to /busbom_status
  • Used by CGI scripts or monitoring processes

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System Architecture

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Requirements

• C++11 or newer
• OpenCV 4.x
• CMake ≥ 3.10
• POSIX threads (pthreads)

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Build Instructions

# Move to the project directory
cd /path/to/platform_observer

# Create and move into the build directory
mkdir -p build
cd build

# Run CMake and build the project
cmake ..
make

Output binary: build/station_checker

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How to Run

1. Live Mode (Default)

Used in production where another process streams frames to /busbom_frame.

./station_checker

2. Video File Mode (Debug)

Used for testing with .mp4 files. Video must be placed under:

/home/Qwd/platform_observer/video/

Example:

./station_checker IMG_4403.mp4

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Processing Pipeline Overview

          +----------------------+
          |   Video Source       | <- Shared Memory or File
          +----------+-----------+
                     |
                [frame_queue]
                     |
              warp_thread
                     ↓
              [warped_queue]
                     ↓
              mask_thread
                     ↓
              [masked_queue]
                     ↓
          Main Thread (Analysis)
                     ↓
         Shared Memory (/busbom_status)

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Detailed Flow Description

1. Video Input

   • Reads from shared memory or a video file into frame_queue

2. ROI Configuration

   • Listens to /tmp/roi_socket for ROI configuration
   • Updates platform count and ROI coordinates in real-time

3. Processing Threads

   • warp_thread: Applies perspective transformation
   • mask_thread: Performs color filtering and masking

4. Detection & Stabilization

   • Evaluates bus presence in each platform ROI
   • Debounces results with time-based confirmation and flicker tolerance

5. Shared Memory Output

   • Writes detection result to /busbom_status
   • Readable by other components such as CGI scripts