evlib 0.5.15

Python bindings for event camera utilities

evlib: Event Camera Data Processing Library

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
  • Basic Usage
  • Advanced Filtering
  • Event Representations
• Installation
  • Basic Installation
  • Development Installation
  • System Dependencies
  • Performance-Optimized Installation
• Polars DataFrame Integration
  • Key Benefits
  • API Overview
    • Loading Data
    • Advanced Features
    • Utility Functions
  • Performance Benchmarks
  • Benchmarking and Monitoring
  • Performance Examples
    • Optimal Loading for Different File Sizes
    • Memory Monitoring
  • Troubleshooting Large Files
    • Memory Constraints
    • Performance Tuning
    • Common Issues and Solutions
• Available Python Modules
  • Core Modules
  • Module Overview
• High-Performance PyTorch DataLoader
  • Key Features
  • Quick Start
  • Architecture Overview
  • Performance Benefits
• Examples
• Development
  • Testing
    • Core Testing
    • Documentation Testing
    • Code Quality
  • Building
    • Requirements
• Community & Support
• License

Quick Start

Basic Usage

import evlib

# Load events from any supported format (automatic detection)
df = evlib.load_events("data/prophersee/samples/evt2/80_balls.raw").collect(engine='streaming')

# Or load as LazyFrame for memory-efficient processing
lf = evlib.load_events("data/prophersee/samples/evt2/80_balls.raw")

# 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 polars as pl

# Load events as LazyFrame for efficient processing
events = evlib.load_events("data/prophersee/samples/evt3/pedestrians.raw")

# Time filtering using Polars operations
time_filtered = events.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 0.1) & (pl.col('time_seconds') <= 0.5)
)

# Spatial filtering (Region of Interest)
spatial_filtered = time_filtered.filter(
    (pl.col('x') >= 100) & (pl.col('x') <= 500) &
    (pl.col('y') >= 100) & (pl.col('y') <= 400)
)

# Polarity filtering
polarity_filtered = spatial_filtered.filter(pl.col('polarity') == 1)

# Collect final results
filtered_df = polarity_filtered.collect()
print(f"Filtered to {len(filtered_df)} events")

Event Representations

evlib provides comprehensive event representation functions for computer vision and neural network applications:

import evlib
import evlib.representations as evr
import polars as pl

# Load events and create representations
events = evlib.load_events("data/prophersee/samples/hdf5/pedestrians.hdf5")
events_df = events.collect()

# Create stacked histogram (replaces RVT preprocessing)
hist = evr.create_stacked_histogram(
    events_df,
    _height=180, _width=240,
    nbins=5, window_duration_ms=50.0,
    _count_cutoff=5
)
print(f"Created stacked histogram with {len(hist)} spatial bins")

# Create mixed density stack representation
density = evr.create_mixed_density_stack(
    events_df,
    _height=180, _width=240,
    nbins=5, window_duration_ms=50.0
)
print(f"Created mixed density stack with {len(density)} entries")

# Create voxel grid representation
voxel = evr.create_voxel_grid(
    events_df,
    _height=180, _width=240,
    nbins=3
)
print(f"Created voxel grid with {len(voxel)} voxels")

# Advanced representations (require data type conversion)
# Convert timestamp and ensure proper dtypes for advanced functions
small_events = events.limit(10000).collect()
converted_events = small_events.with_columns([
    pl.col('timestamp').dt.total_microseconds().cast(pl.Float64).alias('t'),
    pl.col('x').cast(pl.Int64),
    pl.col('y').cast(pl.Int64),
    pl.col('polarity').cast(pl.Int64)
]).drop('timestamp')

# Create time surface representation
time_surface = evr.create_timesurface(
    converted_events,
    height=180, width=240,
    dt=50000.0,    # time step in microseconds
    tau=10000.0    # decay constant in microseconds
)
print(f"Created time surface with {len(time_surface)} pixels")

# Create averaged time surface
avg_time_surface = evr.create_averaged_timesurface(
    converted_events,
    height=180, width=240,
    cell_size=1, surface_size=1,
    time_window=50000.0, tau=10000.0
)
print(f"Created averaged time surface with {len(avg_time_surface)} pixels")

Installation

Basic Installation

pip install evlib

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

# For PyTorch integration
pip install evlib[pytorch]

Development Installation

We recommend using uv for fast, reliable Python package management:

# Install uv (if not already installed)
curl -LsSf https://astral.sh/uv/install.sh | sh

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

# Create virtual environment and install dependencies
uv venv --python 3.12
source .venv/bin/activate  # On Windows: .venv\Scripts\activate
uv 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 (using uv)
uv 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
uv pip install psutil

# For parallel processing (already included in dev)
uv 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/prophersee/samples/evt2/80_balls.raw")
df = events.collect()  # Collect to DataFrame when needed

# Automatic format detection and optimization
events = evlib.load_events("data/prophersee/samples/evt2/80_balls.raw")  # EVT2 format automatically detected
print(f"Format: {evlib.formats.detect_format('data/prophersee/samples/evt2/80_balls.raw')}")
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/prophersee/samples/hdf5/pedestrians.hdf5")
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()

# Complex filtering operations with Polars
filtered = events.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 0.1) & (pl.col('time_seconds') <= 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/prophersee/samples/evt3/pedestrians.raw")
print(f"Detected format: {format_info}")

# Spatial filtering using Polars operations
events = evlib.load_events("data/prophersee/samples/evt3/pedestrians.raw")
spatial_filtered = events.filter(
    (pl.col("x") >= 100) & (pl.col("x") <= 200) &
    (pl.col("y") >= 50) & (pl.col("y") <= 150)
)

# Chain multiple filters efficiently
complex_filtered = events.filter(
    (pl.col("x") >= 100) & (pl.col("x") <= 200) &
    (pl.col("y") >= 50) & (pl.col("y") <= 150) &
    (pl.col("polarity") == 1)
)

# 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 (working example)
processed = events.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 0.1) & (pl.col('time_seconds') <= 0.5)
)
processed_df = processed.collect()
data_arrays = processed_df.select(["x", "y", "timestamp", "polarity"]).to_numpy()
x, y, t_us, p = data_arrays.T
# Convert Duration microseconds to seconds for save function
t = t_us.astype('float64') / 1_000_000
evlib.formats.save_events_to_hdf5(x.astype('int16'), y.astype('int16'), t, p.astype('int8'), "output.h5")

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/prophersee/samples/evt2/80_balls.raw')
df = events.collect()
print(f'Loaded {len(df):,} events in {time.time()-start:.2f}s')
print(f'Format: {evlib.detect_format(\"data/prophersee/samples/evt2/80_balls.raw\")}')
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/prophersee/samples/evt2/80_balls.raw")
df_small = events_small.collect()

# Large files (>5M events) - Automatic streaming
events_large = evlib.load_events("data/prophersee/samples/hdf5/pedestrians.hdf5")
# Same API, automatically uses streaming for memory efficiency

# Memory-efficient filtering on large datasets using Polars
filtered = events_large.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 1.0) & (pl.col('time_seconds') <= 2.0)
)
positive_events = filtered.filter(pl.col("polarity") == 1)

# Collect only when needed for memory efficiency
result_df = positive_events.collect()
print(f"Filtered to {len(result_df)} events")

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/prophersee/samples/evt3/pedestrians.raw")
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/prophersee/samples/hdf5/pedestrians.hdf5")
# Streaming activates automatically for files >5M events

# Apply filtering before collecting to reduce memory usage
filtered = events.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 0.1) & (pl.col('time_seconds') <= 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
events = evlib.load_events("data/prophersee/samples/evt2/80_balls.raw")

# Use Polars operations for optimized filtering
result = events.filter(
    (pl.col("x") >= 0) & (pl.col("x") <= 640) &
    (pl.col("y") >= 0) & (pl.col("y") <= 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/prophersee/samples/evt3/pedestrians.raw")
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/prophersee/samples/evt3/pedestrians.raw")
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/prophersee/samples/hdf5/pedestrians.hdf5")

# Format detection and description
format_info = evlib.formats.detect_format("data/prophersee/samples/hdf5/pedestrians.hdf5")
description = evlib.formats.get_format_description("HDF5")

# Advanced filtering using Polars operations
filtered = events.with_columns([
    (pl.col('timestamp').dt.total_microseconds() / 1_000_000).alias('time_seconds')
]).filter(
    (pl.col('time_seconds') >= 0.1) & (pl.col('time_seconds') <= 0.5)
)
time_filtered = filtered.collect()

# Event representations (working examples)
events_df = events.collect()
hist = evr.create_stacked_histogram(events_df, _height=180, _width=240, nbins=5)
voxel = evr.create_voxel_grid(events_df, _height=180, _width=240, nbins=3)

# Advanced representations (with proper data conversion)
small_events = events.limit(10000).collect()
converted_events = small_events.with_columns([
    pl.col('timestamp').dt.total_microseconds().cast(pl.Float64).alias('t'),
    pl.col('x').cast(pl.Int64),
    pl.col('y').cast(pl.Int64),
    pl.col('polarity').cast(pl.Int64)
]).drop('timestamp')
time_surface = evr.create_timesurface(converted_events, height=180, width=240, dt=50000.0, tau=10000.0)

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

# Data saving (working examples)
df = events.collect()
data_arrays = df.select(["x", "y", "timestamp", "polarity"]).to_numpy()
x, y, t_us, p = data_arrays.T
# Convert Duration microseconds to seconds for save functions
t = t_us.astype('float64') / 1_000_000
evlib.formats.save_events_to_hdf5(x.astype('int16'), y.astype('int16'), t, p.astype('int8'), "output.h5")
evlib.formats.save_events_to_text(x.astype('int16'), y.astype('int16'), t, p.astype('int8'), "output.txt")

High-Performance PyTorch DataLoader

evlib includes an optimized PyTorch dataloader implementation that showcases best practices for event camera data processing:

Key Features

• Polars → PyTorch Integration: Native .to_torch() conversion for zero-copy data transfer
• RVT Preprocessing: Loads real RVT (Recurrent Vision Transformer) preprocessed data
• Statistical Feature Extraction: Efficiently extracts 91 features from stacked histograms
• High Throughput: Achieves 13,000+ samples/sec training throughput
• Memory Efficient: Lazy evaluation and batched processing

Quick Start

# New: Use the built-in PyTorch integration
from evlib.pytorch import create_dataloader, load_rvt_data

# Option 1: One-liner for RVT data
dataloader = create_dataloader("data/gen4_1mpx_processed_RVT/val/moorea_2019-02-21_000_td_2257500000_2317500000",
                              data_type="rvt", batch_size=256)

# Option 2: Manual setup for custom transforms
lazy_df = load_rvt_data("data/gen4_1mpx_processed_RVT/val/moorea_2019-02-21_000_td_2257500000_2317500000")

# Option 3: Raw event data
import evlib
events = evlib.load_events("path/to/events.h5")
dataloader = create_dataloader(events, data_type="events")

# Define transform to extract features and labels from LazyFrame
def split_features_labels(batch):
    """Transform to separate RVT features and labels from Polars batch"""
    feature_tensors = []

    # Add all temporal bin features (mean, std, max, nonzero for each bin)
    for bin_idx in range(20):
        for stat in ["mean", "std", "max", "nonzero"]:
            key = f"bin_{bin_idx:02d}_{stat}"
            if key in batch:
                feature_tensors.append(batch[key])

    # Add bounding box features
    for key in ["bbox_x", "bbox_y", "bbox_w", "bbox_h", "bbox_area"]:
        if key in batch:
            feature_tensors.append(batch[key])

    # Add activity features
    for key in ["total_activity", "active_pixels", "temporal_center"]:
        if key in batch:
            feature_tensors.append(batch[key])

    # Add normalized features
    for key in ["timestamp_norm", "bbox_area_norm", "activity_norm"]:
        if key in batch:
            feature_tensors.append(batch[key])

    # Stack into feature matrix and extract labels
    features = torch.stack(feature_tensors, dim=1)  # Shape: (batch_size, 91)
    labels = batch["label"].long()                  # Shape: (batch_size,)

    return {"features": features, "labels": labels}

# Create efficient dataloader with transform
dataset = PolarsDataset(lazy_df, batch_size=256, shuffle=True,
                       transform=split_features_labels, drop_last=True)
dataloader = DataLoader(dataset, batch_size=None, num_workers=0)

# Train with real event camera data
for batch in dataloader:
    features = batch["features"]  # Shape: (256, 91) - 91 statistical features
    labels = batch["labels"]      # Shape: (256,) - object class labels

    # Your PyTorch training loop here
    outputs = model(features)
    loss = criterion(outputs, labels)
    # ... backward pass, optimizer step, etc.

Architecture Overview

RVT HDF5 Data → Feature Extraction → Polars LazyFrame → .to_torch() → PyTorch Training

The dataloader demonstrates:

• Loading compressed HDF5 event representations (1198 samples, 20 temporal bins, 360×640 resolution)
• Statistical feature extraction (mean, std, max, nonzero) per temporal bin
• Object detection labels with bounding boxes and confidence scores
• Polars LazyFrame operations for memory-efficient processing
• Native PyTorch tensor conversion for optimal performance

Performance Benefits

• 95%+ accuracy on real 3-class classification tasks
• 13,262 samples/sec training throughput
• Memory efficient processing of large event datasets
• Zero-copy conversion between Polars and PyTorch

See examples/polars_pytorch_simplified.py for the complete implementation and adapt it for your own event camera datasets.

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

# Run the high-performance PyTorch dataloader example
python examples/polars_pytorch_simplified.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

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

License

MIT License - see LICENSE.md for details.