OrbbecSDK_v2

C Sample: 1.c_lidar_stream

Overview

This C language sample demonstrates how to configure and stream LiDAR and IMU sensor data using the SDK C API, providing interactive sensor selection and real-time data monitoring.

Knowledge

• C API Streaming uses callback-based frame processing similar to C++ but with manual memory management
• Interactive Configuration allows users to select sensors and stream profiles at runtime
• Multi-sensor Support handles LiDAR point cloud, accelerometer, and gyroscope data
• Frame Processing includes coordinate conversion and valid point counting

Code overview

1. Initialize context and device selection

    ob_context *context = ob_create_context(&error);
    ob_device_list* deviceList = ob_query_device_list(context, &error);
    ob_device *device = selectDevice(deviceList, error);
   

2. Initialize pipeline and configuration with frame aggregation

    ob_pipeline *pipe = ob_create_pipeline_with_device(device, &error);
    ob_device *device = ob_pipeline_get_device(pipe, &error);
    ob_config *config = ob_create_config(&error);
       
    ob_config_set_frame_aggregate_output_mode(config, OB_FRAME_AGGREGATE_OUTPUT_ALL_TYPE_FRAME_REQUIRE, &error);
    ob_config_disable_all_stream(config, &error);
   

3. Set/Get property

    // Get property
    ob_device_get_structured_data(device, OB_STRUCT_DEVICE_SERIAL_NUMBER, data, &data_size, &error);
    // Set property
    ob_device_set_int_property(device, OB_PROP_LIDAR_TAIL_FILTER_LEVEL_INT, 0, &error);
   

4. Interactive sensor and stream profile selection

    select_sensors_and_streams(device, config);
    ob_pipeline_start_with_callback(pipe, config, frame_callback, NULL, &error);
   

5. Frame callback with multi-sensor data processing

    void frame_callback(ob_frame *frameset, void *user_data) {
        uint32_t count = ob_frameset_get_count(frameset, &error);
           
        for(uint32_t i = 0; i < count; i++) {
            ob_frame *frame = ob_frameset_get_frame_by_index(frameset, i, &error);
            ob_frame_type frame_type = ob_frame_get_type(frame, &error);
               
            switch(frame_type) {
            case OB_FRAME_LIDAR_POINTS:
                print_lidar_point_cloud_info(frame);
                break;
            case OB_FRAME_ACCEL:
                // Process accelerometer data
                break;
            case OB_FRAME_GYRO:
                // Process gyroscope data
                break;
            }
               
            ob_delete_frame(frame, &error);
        }
           
        ob_delete_frame(frameset, &error);
    }
   

6. LiDAR point cloud processing with coordinate conversion

    void print_lidar_point_cloud_info(ob_frame *point_cloud_frame) {
        ob_format point_cloud_type = ob_frame_get_format(point_cloud_frame, &error);
           
        if(point_cloud_type == OB_FORMAT_LIDAR_SPHERE_POINT) {
            // Spherical to Cartesian conversion
            float x = (float)(distance * cos(theta_rad) * cos(phi_rad));
            float y = (float)(distance * sin(theta_rad) * cos(phi_rad));
            float z = (float)(distance * sin(phi_rad));
        }
        else if(point_cloud_type == OB_FORMAT_LIDAR_SCAN) {
            // Polar to Cartesian conversion
            float x = (float)(distance * cos(angle_rad));
            float y = (float)(distance * sin(angle_rad));
        }
           
        printf("valid point count = %u\n", valid_point_count);
    }
   

Run Sample

Operation Instructions

1. Sensor Selection: Program displays available sensors and prompts for selection
2. Stream Configuration: Choose from available stream profiles for each sensor
3. Real-time Monitoring: Data from selected sensors is displayed every 50 frames
4. Exit: Press ESC key to stop streaming and exit

Interactive Features

• Sensor List: Displays all available sensors with type information
• Stream Profiles: Shows available formats and parameters for each sensor
• Flexible Selection: Choose individual sensors or enable all available
• Input Validation: Ensures valid selections with proper error handling

Data Processing

• LiDAR Point Cloud: Handles multiple formats (spherical, Cartesian, scan) with coordinate conversion
• IMU Data: Processes accelerometer and gyroscope readings with temperature data
• Valid Point Counting: Filters and counts valid 3D points in point cloud data
• Frame Statistics: Displays frame indices, timestamps, and format information

Result

The program provides a comprehensive C-based streaming solution that:

• Enables interactive sensor configuration without code modification
• Processes multiple sensor types simultaneously with proper synchronization
• Demonstrates coordinate system conversions for different LiDAR data formats
• Maintains C API best practices with proper error handling and memory management
• Offers real-time monitoring of sensor data quality and performance

This sample serves as a foundation for building C applications that require flexible sensor configuration and real-time data processing capabilities.

Device List:
0. name: LiDAR ME450, vid: 0x2bc5, pid: 0x1302, uid: 0x20:4b:5e:00:43:09, sn: T0H6851001Z
1. name: LiDAR ME450, vid: 0x2bc5, pid: 0x1302, uid: 0x20:4b:5e:13:64:30, sn: T0H6851000Z
Select a device: 1

------------------------------------------------------------------------
Current Device: name: LiDAR ME450, vid: 0x2bc5, pid: 0x1302, uid: 0x20:4b:5e:13:64:30, sn: T0H6851000Z
LiDAR IP Address: 192.168.1.100

Sensor list:
 - 0. sensor type: Accel
 - 1. sensor type: Gyro
 - 2. sensor type: LiDAR
 - 3. all sensors

Select a sensor to enable (Input index or 'q' to exit): 3
Stream profile list for sensor Accel:
 - 0. format: ACCEL,  fps: 50_HZ
 - 1. format: ACCEL,  fps: 25_HZ
 - 2. format: ACCEL,  fps: 100_HZ
 - 3. format: ACCEL,  fps: 200_HZ

Select a stream profile to enable (Input index or 'q' to exit): 0
Stream profile list for sensor Gyro:
 - 0. format: GYRO,  fps: 50_HZ
 - 1. format: GYRO,  fps: 25_HZ
 - 2. format: GYRO,  fps: 100_HZ
 - 3. format: GYRO,  fps: 200_HZ

Select a stream profile to enable (Input index or 'q' to exit): 0
Stream profile list for sensor LiDAR:
 - 0. format: LIDAR_SPHERE_POINT,  scan rate: 20HZ
 - 1. format: LIDAR_POINT,  scan rate: 20HZ
 - 2. format: LIDAR_SPHERE_POINT,  scan rate: 15HZ
 - 3. format: LIDAR_POINT,  scan rate: 15HZ
 - 4. format: LIDAR_SPHERE_POINT,  scan rate: 10HZ
 - 5. format: LIDAR_POINT,  scan rate: 10HZ

Select a stream profile to enable (Input index or 'q' to exit): 0
Streams have been started!
Press ESC to exit!
LiDAR PointCloud Frame:
{
  frame index: 1
  tsp = 1761620162421700
  format = 36
  valid point count = 6218
}

Accel Frame:
{
  frame index = 5
  tsp = 1761620162427200
  temperature = 49.33 C
  x = -0.014038 m/s^2
  y = -0.000977 m/s^2
  z = -0.976196 m/s^2
}

Gyro Frame:
{
  frame index = 5
  tsp = 1761620162427200
  temperature = 49.33 C
  x = -0.091553 rad/s
  y = -0.358582 rad/s
  z = -0.251770 rad/s
}

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