evlib

`evlib`: Event Camera Data Processing Library

[![PyPI Version](https://img.shields.io/pypi/v/evlib.svg)](https://pypi.org/project/evlib/) [![Python Versions](https://img.shields.io/pypi/pyversions/evlib.svg)](https://pypi.org/project/evlib/) [![Documentation](https://readthedocs.org/projects/evlib/badge/?version=latest)](https://evlib.readthedocs.io/en/latest/?badge=latest) [![Python](https://github.com/tallamjr/evlib/actions/workflows/pytest.yml/badge.svg)](https://github.com/tallamjr/evlib/actions/workflows/pytest.yml) [![Rust](https://github.com/tallamjr/evlib/actions/workflows/rust.yml/badge.svg)](https://github.com/tallamjr/evlib/actions/workflows/rust.yml) [![License](https://img.shields.io/github/license/tallamjr/evlib)](https://github.com/tallamjr/evlib/blob/master/LICENSE.md)

An event camera processing library with Rust backend and Python bindings, designed for scalable data processing with real-world event camera datasets.

Core Features

Universal Format Support: Load data from H5, AEDAT, EVT2/3, AER, and text formats
Automatic Format Detection: No need to specify format types manually
Polars DataFrame Integration: High-performance DataFrame operations with up to 360M events/s filtering
Event Filtering: Comprehensive filtering with temporal, spatial, and polarity options
Event Representations: Stacked histograms, voxel grids, and mixed density stacks
Neural Network Models: E2VID model loading and inference
Real-time Data Processing: Handle large datasets (550MB+ files) efficiently
Polarity Encoding: Automatic conversion between 0/1 and -1/1 polarities
Rust Performance: Memory-safe, high-performance backend with Python bindings

In Development: Advanced neural network processing (hopefully with Rust backend, maybe Candle) Real-time visualization (Only simulated working at the moment — see wasm-evlib)

Note: The Rust backend currently focuses on data loading and processing, with Python modules providing advanced features like filtering and representations.

Quick Start
Installation
Polars DataFrame Integration
Available Python Modules
- Core Modules
- Module Overview
Examples
Development
- Testing
- Building
  - Requirements
Community & Support
License

Quick Start

Basic Usage

import evlib

# Load events from any supported format (automatic detection)
df = evlib.load_events("data/slider_depth/events.txt").collect(engine='streaming')

# Or load as LazyFrame for memory-efficient processing
lf = evlib.load_events("data/slider_depth/events.txt")

# Basic event information
print(f"Loaded {len(df)} events")
print(f"Resolution: {df['x'].max()} x {df['y'].max()}")
print(f"Duration: {df['timestamp'].max() - df['timestamp'].min()}")

# Convert to NumPy arrays for compatibility
x_coords = df['x'].to_numpy()
y_coords = df['y'].to_numpy()
timestamps = df['timestamp'].to_numpy()
polarities = df['polarity'].to_numpy()

Advanced Filtering

import evlib
import evlib.filtering as evf

# High-level preprocessing pipeline
processed = evlib.filtering.preprocess_events(
    "data/slider_depth/events.txt",
    t_start=0.1, t_end=0.5,
    roi=(100, 500, 100, 400),
    polarity=1,
    remove_hot_pixels=True,
    remove_noise=True,
    hot_pixel_threshold=99.9,
    refractory_period_us=1000
)

# Individual filters (work with LazyFrames)
events = evlib.load_events("data/slider_depth/events.txt")
time_filtered = evlib.filtering.filter_by_time(events, t_start=0.1, t_end=0.5)
spatial_filtered = evlib.filtering.filter_by_roi(time_filtered, x_min=100, x_max=500, y_min=100, y_max=400)
clean_events = evlib.filtering.filter_hot_pixels(spatial_filtered, threshold_percentile=99.9)
denoised = evlib.filtering.filter_noise(clean_events, method="refractory", refractory_period_us=1000)

Event Representations

import evlib
import evlib.representations as evr

# Create voxel grid representation (reliable alternative to stacked histogram)
events = evlib.load_events("data/slider_depth/events.txt")
events_df = events.collect()
voxel_df = evr.create_voxel_grid_py(
    events_df,
    _height=480, _width=640,
    nbins=10
)

# Create mixed density stack representation
mixed_df = evr.create_mixed_density_stack_py(
    events_df,
    _height=480, _width=640,
    nbins=10, window_duration_ms=50.0
)
print(f"Created voxel grid with {len(voxel_df)} entries and mixed density stack with {len(mixed_df)} entries")

# High-level preprocessing for neural networks
events = evlib.load_events("data/slider_depth/events.txt")
events_df = events.collect()
data_df = evr.create_voxel_grid_py(
    events_df,
    _height=480, _width=640,
    nbins=10
)
print(f"Preprocessed {len(data_df)} entries for detection pipeline")

# Performance benchmarking against RVT (manual comparison available)
import time

start_time = time.time()
events = evlib.load_events("data/slider_depth/events.txt")
events_df = events.collect()
results_df = evr.create_voxel_grid_py(events_df, _height=480, _width=640, nbins=10)
processing_time = time.time() - start_time

print(f"evlib processing: {processing_time:.3f}s for {len(results_df)} voxel grid entries")
print("Implement equivalent RVT PyTorch pipeline for direct comparison")

Installation

Basic Installation

pip install evlib

# For Polars DataFrame support (recommended)
pip install evlib[polars]

Development Installation

# Clone the repository
git clone https://github.com/tallamjr/evlib.git
cd evlib

# Create virtual environment
python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

# Install in development mode with all features
pip install -e ".[dev,polars]"

# Build the Rust extensions
maturin develop

System Dependencies

# Ubuntu/Debian
sudo apt install libhdf5-dev pkg-config

# macOS
brew install hdf5 pkg-config

Performance-Optimized Installation

For optimal performance, ensure you have the recommended system configuration:

System Requirements:

RAM: 8GB+ recommended for files >100M events
Python: 3.10+ (3.12 recommended for best performance)
Polars: Latest version for advanced DataFrame operations

Installation for Performance:

# Install with Polars support (recommended)
pip install "evlib[polars]"

# For development with all performance features
pip install "evlib[dev,polars]"

# Verify installation with benchmark
python -c "import evlib; print('evlib installed successfully')"
python benchmark_memory.py  # Test memory efficiency

Optional Performance Dependencies:

# For advanced memory monitoring
pip install psutil

# For parallel processing (already included in dev)
pip install multiprocessing-logging

Polars DataFrame Integration

evlib provides comprehensive Polars DataFrame support for high-performance event data processing:

Key Benefits

Performance: 1.9M+ events/s loading speed, 360M+ events/s filtering speed
Memory Efficiency: ~23 bytes/event (5x better than typical 110 bytes/event)
Expressive Queries: SQL-like operations for complex data analysis
Lazy Evaluation: Query optimization for better performance
Ecosystem Integration: Seamless integration with data science tools

API Overview

Loading Data

import evlib

# Load as LazyFrame (recommended)
events = evlib.load_events("data/slider_depth/events.txt")
df = events.collect()  # Collect to DataFrame when needed

# Automatic format detection and optimization
events = evlib.load_events("data/slider_depth/events.txt")  # EVT2 format automatically detected
print(f"Format: {evlib.formats.detect_format('data/slider_depth/events.txt')}")
print(f"Description: {evlib.formats.get_format_description('EVT2')}")

Advanced Features

import evlib
import polars as pl

# Chain operations with LazyFrames for optimal performance
events = evlib.load_events("data/slider_depth/events.txt")
result = events.filter(pl.col("polarity") == 1).with_columns([
    pl.col("timestamp").dt.total_microseconds().alias("time_us"),
    (pl.col("x") + pl.col("y")).alias("diagonal_pos")
]).collect()

# Memory-efficient temporal analysis
time_stats = events.with_columns([
    pl.col("timestamp").dt.total_microseconds().alias("time_us")
]).group_by([
    (pl.col("time_us") // 1_000_000).alias("time_second")  # Group by second
]).agg([
    pl.len().alias("event_count"),
    pl.col("polarity").mean().alias("avg_polarity")
]).collect()

# Combine with filtering module for complex operations
import evlib.filtering as evf
filtered = evlib.filtering.filter_by_time(events, t_start=0.1, t_end=0.5)
analysis = filtered.with_columns([
    pl.col("timestamp").dt.total_microseconds().alias("time_us")
]).collect()

Utility Functions

import evlib
import polars as pl
import evlib.filtering as evf

# Built-in format detection
format_info = evlib.formats.detect_format("data/slider_depth/events.txt")
print(f"Detected format: {format_info}")

# Spatial filtering using dedicated filtering functions (preferred)
events = evlib.load_events("data/slider_depth/events.txt")
spatial_filtered = evlib.filtering.filter_by_roi(events, x_min=100, x_max=200, y_min=50, y_max=150)

# Or using direct Polars operations
manual_filtered = events.filter(
    (pl.col("x") >= 100) & (pl.col("x") <= 200) &
    (pl.col("y") >= 50) & (pl.col("y") <= 150)
)

# Temporal analysis with Polars operations
rates = events.with_columns([
    pl.col("timestamp").dt.total_microseconds().alias("time_us")
]).group_by([
    (pl.col("time_us") // 10_000).alias("time_10ms")  # Group by 10ms
]).agg([
    pl.len().alias("event_rate"),
    pl.col("polarity").mean().alias("avg_polarity")
]).collect()

# Save processed data
processed = evlib.filtering.preprocess_events("data/slider_depth/events.txt", t_start=0.1, t_end=0.5)
processed_df = processed.collect()
x, y, t_us, p = processed_df.select(["x", "y", "timestamp", "polarity"]).to_numpy().T
# Ensure correct dtypes for save function
x = x.astype(np.int64)
y = y.astype(np.int64)
p = p.astype(np.int64)
# Convert microseconds to seconds for save function
t = t_us.astype(np.float64) / 1_000_000
evlib.formats.save_events_to_hdf5(x, y, t, p, "output.h5")
print(f"Successfully saved {len(x)} processed events to HDF5")

Performance Benchmarks

Benchmark Results:

Loading Speed: 1.9M+ events/second average across formats
Filter Speed: 360M+ events/second for complex filtering operations
Memory Efficiency: ~23 bytes/event
Format Performance: RAW binary (2.6M events/s) > HDF5 (2.5M events/s) > Text (0.6M events/s)

Benchmarking and Monitoring

Run performance benchmarks to verify optimizations:

# Verify README performance claims and generate plots
python benches/benchmark_performance_readme.py

# Memory efficiency benchmark
python benches/benchmark_memory.py

# Test with your own data
python -c "
import evlib
import time
start = time.time()
events = evlib.load_events('data/slider_depth/events.txt')
df = events.collect()
print(f'Loaded {len(df):,} events in {time.time()-start:.2f}s')
print(f'Format: {evlib.detect_format(\"data/slider_depth/events.txt\")}')
print(f'Memory per event: {df.estimated_size() / len(df):.1f} bytes')
"

Performance Examples

Optimal Loading for Different File Sizes

import evlib
import evlib.filtering as evf
import polars as pl

# Small files (<5M events) - Direct loading
events_small = evlib.load_events("data/slider_depth/events.txt")
df_small = events_small.collect()

# Large files (>5M events) - Automatic streaming
events_large = evlib.load_events("data/slider_depth/events.txt")
# Same API, automatically uses streaming for memory efficiency

# Memory-efficient filtering on large datasets using filtering module
filtered = evlib.filtering.filter_by_time(events_large, t_start=1.0, t_end=2.0)
positive_events = evlib.filtering.filter_by_polarity(filtered, polarity=1)

# Or using direct Polars operations
manual_filtered = events_large.filter(
    (pl.col("timestamp").dt.total_microseconds() / 1_000_000 > 1.0) &
    (pl.col("polarity") == 1)
).collect()

Memory Monitoring

import evlib
import psutil
import os

def monitor_memory():
    process = psutil.Process(os.getpid())
    return process.memory_info().rss / 1024 / 1024  # MB

# Monitor memory usage during loading
initial_mem = monitor_memory()
events = evlib.load_events("data/slider_depth/events.txt")
df = events.collect()
peak_mem = monitor_memory()

print(f"Memory used: {peak_mem - initial_mem:.1f} MB")
print(f"Memory per event: {(peak_mem - initial_mem) * 1024 * 1024 / len(df):.1f} bytes")
print(f"Polars DataFrame size: {df.estimated_size() / 1024 / 1024:.1f} MB")

Troubleshooting Large Files

Memory Constraints

Automatic Streaming: Files >5M events use streaming by default
LazyFrame Operations: Memory-efficient processing without full materialization
Memory Monitoring: Use benchmark_memory.py to track usage
System Requirements: Recommend 8GB+ RAM for files >100M events

Performance Tuning

Optimal Chunk Size: System automatically calculates based on available memory
LazyFrame Operations: Use .lazy() for complex filtering chains
Memory-Efficient Formats: RAW binary formats provide best performance, followed by HDF5
Progress Reporting: Large files show progress during loading

Common Issues and Solutions

Issue: Out of memory errors

import evlib
import evlib.filtering as evf

# Solution: Use filtering before collecting (streaming activates automatically)
events = evlib.load_events("data/slider_depth/events.txt")
# Streaming activates automatically for files >5M events

# Apply filtering before collecting to reduce memory usage
filtered = evlib.filtering.filter_by_time(events, t_start=0.1, t_end=0.5)
df = filtered.collect()  # Only collect when needed

# Or stream to disk using Polars
filtered.sink_parquet("filtered_events.parquet")

Issue: Slow loading performance

import evlib
import evlib.filtering as evf
import polars as pl

# Solution: Use LazyFrame for complex operations and filtering module
events = evlib.load_events("data/slider_depth/events.txt")

# Use filtering module for optimized operations
result = evlib.filtering.filter_by_roi(events, x_min=0, x_max=640, y_min=0, y_max=480)
df = result.collect()

# Or chain Polars operations
result = events.filter(pl.col("polarity") == 1).select(["x", "y", "timestamp"]).collect()

Issue: Memory usage higher than expected

import evlib

# Solution: Monitor and verify optimization
events = evlib.load_events("data/slider_depth/events.txt")
df = events.collect()
print(f"Memory efficiency: {df.estimated_size() / len(df)} bytes/event")
print(f"DataFrame schema: {df.schema}")
print(f"Number of events: {len(df):,}")

# Check format detection
format_info = evlib.formats.detect_format("data/slider_depth/events.txt")
print(f"Format: {format_info}")

Available Python Modules

evlib provides several Python modules for different aspects of event processing:

Core Modules

evlib.formats: Direct Rust access for format loading and detection
evlib.filtering: High-performance event filtering with Polars
evlib.representations: Event representations (stacked histograms, voxel grids)
evlib.models: Neural network model loading and inference (Under construction)

Module Overview

import evlib
import evlib.filtering as evf
import evlib.representations as evr

# Core event loading (returns Polars LazyFrame)
events = evlib.load_events("data/slider_depth/events.txt")

# Format detection and description
format_info = evlib.formats.detect_format("data/slider_depth/events.txt")
description = evlib.formats.get_format_description("HDF5")

# Advanced filtering
filtered = evlib.filtering.preprocess_events("data/slider_depth/events.txt", t_start=0.1, t_end=0.5)
time_filtered = evlib.filtering.filter_by_time(events, t_start=0.1, t_end=0.5)

# Event representations
events = evlib.load_events("data/slider_depth/events.txt")
events_df = events.collect()
voxel_df = evr.create_voxel_grid_py(events_df, _height=480, _width=640, nbins=10)
mixed_df = evr.create_mixed_density_stack_py(events_df, _height=480, _width=640, nbins=10)
print(f"Created voxel grid with {len(voxel_df)} entries and mixed density stack with {len(mixed_df)} entries")

# Neural network models (limited functionality)
# from evlib.models import ModelConfig  # If available - under development

# Data saving (need to get arrays first)
import numpy as np
df = events.collect()
x, y, t_dur, p = df.select(["x", "y", "timestamp", "polarity"]).to_numpy().T
# Ensure correct dtypes for save functions
x = x.astype(np.int64)
y = y.astype(np.int64)
p = p.astype(np.int64)
# Convert Duration to seconds for save functions
t = t_dur.astype('float64') / 1e6  # Convert microseconds to seconds
evlib.formats.save_events_to_hdf5(x, y, t, p, "output.h5")
evlib.formats.save_events_to_text(x, y, t, p, "output.txt")
print(f"Successfully saved {len(x)} events to both HDF5 and text formats")

Examples

Run examples:

# Test all notebooks
pytest --nbmake examples/

# Run specific examples
python examples/simple_example.py
python examples/filtering_demo.py
python examples/stacked_histogram_demo.py

Development

Testing

Core Testing

# Run all tests (Python and Rust)
pytest
cargo test

# Test specific modules
pytest tests/test_filtering.py
pytest tests/test_representations.py
pytest tests/test_evlib_exact_match.py

# Test notebooks (including examples)
pytest --nbmake examples/

# Test with coverage
pytest --cov=evlib

Documentation Testing

All code examples in the documentation are automatically tested to ensure they work correctly:

# Test all documentation examples
pytest --markdown-docs docs/

# Test specific documentation file
pytest --markdown-docs docs/getting-started/quickstart.md

# Use the convenient test script
python scripts/test_docs.py --list    # List testable files
python scripts/test_docs.py --report  # Generate report

# Test specific documentation section
pytest --markdown-docs docs/user-guide/
pytest --markdown-docs docs/getting-started/

Code Quality

# Format code
black python/ tests/ examples/
cargo fmt

# Run linting
ruff check python/ tests/
cargo clippy

# Check types
mypy python/evlib/

Building

Requirements

Rust: Stable toolchain (see rust-toolchain.toml)
Python: ≥3.10 (3.12 recommended)
Maturin: For building Python extensions

# Development build
maturin develop --features python # python required to register python modules

# Build with features
maturin develop --features polars
maturin develop --features pytorch

# Release build
maturin build --release

Community & Support

xkcd { width=100% }

GitHub: tallamjr/evlib
Issues: Report bugs and request features
Discussions: Community Q&A and ideas

License

MIT License - see LICENSE.md for details.

This site is open source. Improve this page.