Added Readme

Author: lucasreljic

deep_tools/camera_sync/README.md

@@ -0,0 +1,98 @@
+# Multi-Camera Synchronization Node
+
+A ROS2 node that uses message filters to time-synchronize N camera image messages, supporting both compressed and raw images.
+
+## Features
+
+- **Flexible camera count**: Supports 2-6 cameras simultaneously
+- **Image format support**: Works with both `sensor_msgs/Image` (raw) and `sensor_msgs/CompressedImage`
+- **Configurable synchronization**: Adjustable time tolerance and queue sizes
+- **Real-time monitoring**: Synchronization statistics and rate monitoring
+- **Easy integration**: Standard ROS2 node with parameter-based configuration
+
+## Parameters
+
+| Parameter | Type | Default | Description |
+|-----------|------|---------|-------------|
+| `camera_topics` | string[] | `[]` | List of camera image topics to synchronize |
+| `camera_names` | string[] | `[]` | Names for cameras (auto-generated if empty) |
+| `use_compressed` | bool | `false` | Use compressed images instead of raw |
+| `sync_tolerance_ms` | double | `50.0` | Max time difference for sync (milliseconds) |
+| `queue_size` | int | `10` | Message filter queue size |
+| `publish_sync_info` | bool | `true` | Publish synchronization statistics |
+
+## Usage
+
+### Basic 2-camera setup (raw images):
+
+```bash
+ros2 run camera_sync multi_camera_sync_node --ros-args \
+  -p camera_topics:="['/camera1/image_raw', '/camera2/image_raw']" \
+  -p camera_names:="['left_camera', 'right_camera']"
+```
+
+### 4-camera setup (compressed images):
+
+```bash
+ros2 run camera_sync multi_camera_sync_node --ros-args \
+  -p camera_topics:="['/front/image_raw/compressed', '/rear/image_raw/compressed', '/left/image_raw/compressed', '/right/image_raw/compressed']" \
+  -p camera_names:="['front', 'rear', 'left', 'right']" \
+  -p use_compressed:=true \
+  -p sync_tolerance_ms:=30.0
+```
+
+### Using launch files:
+
+```bash
+# Basic launch with configurable parameters
+ros2 launch camera_sync multi_camera_sync.launch.py \
+  camera_topics:="['/cam1/image_raw', '/cam2/image_raw', '/cam3/image_raw']" \
+  use_compressed:=false \
+  sync_tolerance_ms:=25.0
+
+```
+
+## How It Works
+
+The node uses ROS2 message filters with approximate time synchronization policy to match images from multiple cameras based on their timestamps. Key components:
+
+1. **Message Subscribers**: Creates subscribers for each camera topic
+2. **Synchronizer**: Uses `message_filters::sync_policies::ApproximateTime` to match messages
+3. **Callback & Publishing**: Creates MultiImage msgs with timestamp to batch the camera images together 
+4. **Statistics**: Tracks synchronization rate and timing spread
+
+### Synchronization Logic
+
+- Messages are considered synchronized if their timestamps are within `sync_tolerance_ms`
+- The synchronizer maintains a queue of recent messages from each camera
+- When a valid sync set is found, all cameras' images are processed together
+- Unmatched messages are eventually dropped when they exceed the age penalty
+
+
+## Monitoring
+
+The node provides several ways to monitor synchronization performance:
+
+1. **Console logs**: Periodic sync rate and timing statistics
+2. **ROS2 parameters**: Runtime inspection of configuration
+3. **Debug output**: Detailed timestamp information (when debug logging enabled)
+
+Example log output:
+```
+[INFO] [multi_camera_sync]: Sync #500: compressed images from 4 cameras, spread: 12.3 ms, rate: 29.8 Hz
+```
+
+## Dependencies
+
+- `rclcpp` - ROS2 C++ client library
+- `sensor_msgs` - Standard sensor message types
+- `message_filters` - Time synchronization utilities
+- `cv_bridge` - OpenCV integration (for future extensions)
+- `image_transport` - Efficient image transmission
+
+## Limitations
+
+- Maximum 6 cameras supported (can be extended by adding more sync policies)
+- Uses approximate time synchronization (not exact)
+- All cameras must use the same image message type (raw or compressed)
+- Requires reasonably synchronized system clocks across camera sources

deep_tools/camera_sync/launch/multi_camera_sync.launch.py

@@ -42,7 +42,7 @@ def generate_launch_description():
 
     use_compressed_arg = DeclareLaunchArgument(
         "use_compressed",
-        default_value="true",
+        default_value="false",
         description="Whether to use compressed images (sensor_msgs/CompressedImage) instead of raw (sensor_msgs/Image)",
     )