BlindNav

Wearable navigation assistant for blind users built for Raspberry Pi 4 + Intel RealSense D435. The system detects obstacles, estimates threat from distance and time-to-collision, and speaks warnings through Bluetooth headphones using Piper neural TTS.

Current production version: v3.30 HEADLESS

• Production script: raspberry_pi/yolo_realsense_navigation.py
• Foundational regression suite: tests/test_blindnav.py
• Advanced voice/latency regression suite: tests/test_blindnav_v326.py
• Verified locally on April 27, 2026: 195 passed

What It Does

• Runs YOLO26n ONNX inference on Pi 4 CPU.
• Samples depth per tracked object using adaptive stride + clustering.
• Compensates apparent approach speed using background-depth ego-motion.
• Suppresses static-object chatter when the user is standing still.
• Speaks left/right/ahead warnings with distance-aware cooldown buckets.
• Logs per-alert latency timestamps to events.log.
• Provides on-demand scene description with the d key.
• Provides optional push-to-talk voice commands with OpenAI speech-to-text.
• Provides an optional OpenAI alert TTS field-test mode.

Recent Changes

v3.30

• Added BLINDNAV_ALERT_TTS=openai as a field-test mode for urgent, warning, and cleared alert speech.
• Keeps detection, threat scoring, voice queueing, and aplay playback policy unchanged so the field test compares TTS output only.
• Uses OpenAI WAV speech output with local fallback enabled by default.
• Added tools/run_tts_local.sh, tools/run_tts_openai.sh, and tools/FIELD_TEST_TTS_COMPARE.md for repeatable side-by-side field tests.

v3.29

• Added optional push-to-talk voice command input with BLINDNAV_VOICE_INPUT=1.
• Records short commands with arecord, transcribes through OpenAI STT, and routes deterministic commands: describe, nearest, people, status, repeat, and cancel.
• Keeps safety alerts on the existing local Piper/VoiceAssistant path by default; OpenAI STT is used only for command input.
• Adds a thread-safe navigation snapshot so command responses can report the nearest object, people count, and runtime status without blocking detection.
• Adds tools/test_transcribe.py for command-line STT smoke testing.

v3.28

• Bucketed spoken distances to the same 30 cm voice buckets already used by cooldown keys so repeat warnings reuse the same Piper phrases instead of synthesizing slightly different decimals.
• Added richer voice diagnostics to events.log, including queue wait, synth time, launch wait, cache hit vs miss, and synthesis mode.
• Made left/right/ahead hysteresis frame-stable so repeated same-frame position reads no longer consume the switch threshold early.
• Promoted nearby side-pass people on the left/right while the user is moving, so a person walking by no longer depends entirely on radial TTC.
• Clamped bad-ego TTC usage to close range when the user is still, blocking far nonsense alerts such as person ahead, 6.4 meters.
• Switched non-person urgent/warning phrasing to cached obstacle wording so close-object warnings stay fast even when the classifier label changes.

v3.27

• Switched urgent/warning alerts to Piper by default while keeping espeak available as an override through BLINDNAV_ALERT_TTS=espeak.
• Added a prewarmed Piper alert-clip cache for common short safety phrases so urgent/warning speech stays natural without paying full synthesis cost every time.
• Kept en_US-amy-medium as the default Piper voice and added env-based voice overrides so lessac-medium can be tested without editing the script.
• Added large-jump confirmation and far-noise suppression so static people at roughly 2-3m do not accumulate fake approach velocity.
• Replaced the thirds-based left/right/ahead split with wide-angle-aware angle mapping plus per-track hysteresis.
• Unified filtered motion across threat scoring, TTC logging, console output, and CSV logging.
• Hardened shutdown so the voice queue drains cleanly and the capture thread is joined before process exit.

v3.25

• Reduced ONNX Runtime to 3 threads so Piper synthesis gets CPU time.
• Added ego-Z clamp and confidence gating to block impossible velocity spikes.
• Switched to zone-based voice cooldown keys so tracker ID churn does not retrigger the same warning.
• Added per-alert latency logging.

v3.26b

• Extracted _select_voice_message() so alert wording is unit-testable.
• Fixed neutral wording leakage in close-distance branches when ego-motion is unreliable.
• Added safe urgent supersession: an urgent alert can cancel a lower-priority phrase only while that phrase is still synthesizing.
• Replaced terminate-style preemption with BT-safe skip-ahead before playback.
• Preserved the hard rule that active aplay playback is never terminated.

Hard Rules

• Never send SIGTERM to aplay.
• Never use numpy 2.0+; pin numpy==1.26.4.
• Never use cv2.imshow on the Pi; use the Flask MJPEG stream for display work.
• Never put the ghost filter inside ObjectTracker.
• Never announce a threat as cleared while its compensated velocity is still negative enough to indicate approach.

Repository Layout

blind_navigation_aid/
|-- AGENTS.md
|-- README.md
|-- SETUP.md
|-- STATUS.md
|-- raspberry_pi/
|   `-- yolo_realsense_navigation.py
|-- tests/
|   |-- test_blindnav.py
|   `-- test_blindnav_v326.py
`-- .github/workflows/tests.yml

Quick Start

source ~/blindnav-venv/bin/activate
export ANTHROPIC_API_KEY="sk-..."
export OPENAI_API_KEY="sk-..."            # optional, for voice commands
export BLINDNAV_VOICE_INPUT=1             # optional, press v to speak command
python3 raspberry_pi/yolo_realsense_navigation.py

Press d for a scene description, or v for a voice command when enabled. Use Ctrl+C to exit.

To compare alert TTS output only:

bash tools/run_tts_local.sh
OPENAI_API_KEY="sk-..." bash tools/run_tts_openai.sh

To upload each completed run's CSV and event log to GitHub automatically:

export BLINDNAV_LOG_UPLOAD=1
python3 raspberry_pi/yolo_realsense_navigation.py

Logs are pushed to the blindnav-field-logs branch by default. Set BLINDNAV_LOG_UPLOAD_BRANCH or BLINDNAV_LOG_UPLOAD_REMOTE to override that. The uploader writes its own upload_*.log file under ~/blindnav_logs. BlindNav keeps the newest 10 navigation runs by default and prunes older log_*.csv / events_*.log pairs on startup and shutdown. Set BLINDNAV_LOG_RETENTION_RUNS to change that. When upload is enabled, startup also retries upload for the newest previous completed run so logs from a prior failed shutdown are not stranded locally.

Tests

All tests run without camera hardware, a RealSense device, Piper, or an IMU. Hardware modules are stubbed at import time.

pytest tests/test_blindnav.py tests/test_blindnav_v326.py -v

Current collected totals:

• tests/test_blindnav.py: 37 tests
• tests/test_blindnav_v326.py: 158 tests
• Combined: 195 tests

Performance Notes

• Expected field FPS: roughly 8-14 depending on thermals.
• YOLO export must produce output shape (1, 300, 6).
• ONNX Runtime stays on float32. INT8 was slower on Pi 4 ARM in project tests.
• Thermal throttling is still the main real-world performance limiter.

Current Priorities

• Add a heatsink before field sessions.
• Review and merge the v3.30 repo state, then field-test it with Ricardo Salazar.
• Record bag-file scenarios for regression playback.
• Field-test push-to-talk voice input on the Pi with the real microphone.
• Field-test local Piper alert TTS against OpenAI alert TTS using the same walking route and compare [LATENCY] play_start in events.log.
• Add traffic-light color classification after the base obstacle system is stable.

Design Notes

• Urgent audio is optimized for freshness, but active playback is not forcibly interrupted because Bluetooth stream renegotiation is worse than waiting for a short phrase to finish.
• Queueing, cooldown, latency, wording, and ego-motion regressions are all testable without hardware and are now covered in the advanced suite.