# Audio Processing Test Tool Design

**Date:** 2026-06-11
**Status:** Design proposal
**TODO:** TODO-044
**Requirements:** SysRS-074, SRS-083
**Effort:** L

## Purpose

Test the audio DSP pipeline (AEC, NS, AGC, HPF) in isolation. Measures processing latency, signal quality, and verifies each filter stage produces expected output for known input signals.

## Inputs

- WAV file (reference signal) or live microphone input
- Processing configuration (enable/disable AEC, NS, AGC, HPF)
- Optional: reference signal for AEC (far-end playback)

## Outputs

- Processed audio WAV file
- Per-stage metrics: latency (ms), signal level (dBFS), spectral changes
- Pass/fail per processing stage against acceptance thresholds

## Architecture

```text
┌──────────┐     ┌───────────────────────────────────────┐     ┌──────────┐
│ WAV /    │────>│ DSP Chain: HPF → NS → AEC → AGC      │────>│ Processed│
│ Mic Input│     │ (chanora_audio processors)             │     │ WAV +    │
└──────────┘     └────────────────────────┬──────────────┘     │ Metrics  │
                                          │                     └──────────┘
                                   ┌──────v───────┐
                                   │ Metrics      │
                                   │ Collector    │
                                   │ (latency,    │
                                   │  dBFS, SNR)  │
                                   └──────────────┘
```

1. **Load:** Read WAV file or open mic stream
2. **Process:** Feed PCM frames through each enabled DSP stage sequentially
3. **Measure:** Collect per-stage latency and signal metrics
4. **Output:** Write processed WAV and print metrics table

## Implementation Plan

- New Rust binary crate: `tools/audio-processing-test/`
- Reuse `chanora_audio` processors: `HpfProcessor`, noise suppression, AEC, AGC
- WAV I/O via `hound` crate
- CLI interface: `audio-processing-test <input.wav> [--output processed.wav] [--stages hpf,ns,aec,agc]`
- Metrics: frame-level latency, input/output RMS, spectral centroid shift

## Dependencies

- `chanora_audio` (HPF, NS, AEC, AGC processors)
- `hound` (WAV read/write)
- `chanora_audio::engine` (AudioProcessingConfig)

## Verification

- Unit test: known-tone input through HPF, verify low-frequency attenuation
- Unit test: known-noise input through NS, verify noise floor reduction
- Integration test: full pipeline on reference WAV, verify output within thresholds
- Demo: run tool on sample file, show metrics output