# Verification record — `audio-capture-playback-android-spike`

## Result

PASS. The mobile half of the PoC plan §2 audio exit criterion
("at least one mobile target") is met on a physical Android device.

This combined with the desktop half (closed by
`poc/audio-capture-playback-spike` on Linux + PipeWire on 2026-05-13)
fully retires the audio PoC.

## Environment

| Field | Value |
|---|---|
| Date | 2026-05-13 |
| Build host OS | Linux (Arch, kernel 7.0.5-arch1-1, x86_64) |
| Rust toolchain | stable 1.95.0 (59807616e 2026-04-14) |
| Android SDK | platform 34, build-tools 34.0.0, platform-tools |
| Android NDK | r26.3.11579264 |
| `cargo-ndk` | 4.1.2 |
| AGP | 8.5.2 |
| Gradle | 8.7 |
| Kotlin | 1.9.24 |
| `cpal` | 0.16 |
| `hound` | 3.5 |
| `jni` | 0.21 |
| `ndk-context` | 0.1.1 |
| `android_logger` | 0.14 |
| Test device | Motorola Moto G Stylus 5G (2023), Android 14 (SDK 34), arm64-v8a (transport_id ZD222DQHFY) |

The Android x86_64 emulator AVD `chanora-poc-api34` was created and
the system image installed, but emulator verification was **skipped
intentionally** once the physical-device run succeeded; the physical
device is stronger evidence than emulator audio HAL.

## Reproduction

```bash
cd poc/audio-capture-playback-android-spike/android
./gradlew :app:assembleDebug
adb install -r app/build/outputs/apk/debug/app-debug.apk
adb shell pm grant app.chanora.poc.audio android.permission.RECORD_AUDIO
adb shell am start -n app.chanora.poc.audio/.MainActivity
adb shell input tap 540 520   # Play
adb shell input tap 540 640   # Record
```

## Observed result

### Playback (PLAY 500 MS SINE)

logcat:

```
ChanoraPoCActivity: playing…
ChanoraAudioPoC: audio_capture_playback_android_spike: playback device='default'
                 sample_rate=44100 channels=2 fmt=F32
ChanoraAudioPoC: audio_capture_playback_android_spike: playSine440 ok n=22050
ChanoraPoCActivity: PLAY OK frames=22050
```

UI status text after tap: `"PLAY OK frames=22050"`.

22,050 frames at 44.1 kHz mono equals exactly 500 ms — the requested
duration. The full Rust → cpal → Oboe → AAudio → speaker path
completed without error.

### Capture (RECORD 1 S TO FILE)

logcat:

```
ChanoraPoCActivity: recording 1 s…
ChanoraAudioPoC: audio_capture_playback_android_spike: capture device='default'
                 sample_rate=44100 channels=2 fmt=F32
ChanoraAudioPoC: audio_capture_playback_android_spike: record1sToFile ok n=42624
ChanoraPoCActivity: RECORD OK frames=42624 bytes=85292
                    path=/data/user/0/app.chanora.poc.audio/files/chanora_poc_capture.wav
```

UI status text after tap: `"RECORD OK frames=42624 bytes=85292
path=/data/user/0/app.chanora.poc.audio/files/chanora_poc_capture.wav"`.

42,624 frames at 44.1 kHz is approximately 966 ms — slightly under
the requested 1 s because `std::thread::sleep` and the cpal callback
boundary do not align perfectly. The full Rust → cpal → Oboe → AAudio
→ microphone path completed without error.

### File integrity

The WAV file was pulled with:

```bash
adb exec-out run-as app.chanora.poc.audio cat files/chanora_poc_capture.wav \
    > /tmp/chanora_capture.wav
```

`file(1)` output:

```
/tmp/chanora_capture.wav: RIFF (little-endian) data, WAVE audio,
                          Microsoft PCM, 16 bit, mono 44100 Hz
```

Header bytes confirm:

```
00000000: 5249 4646 244d 0100 5741 5645 666d 7420  RIFF$M..WAVEfmt
00000010: 1000 0000 0100 0100 44ac 0000 8858 0100  ........D....X..
00000020: 0200 1000 6461 7461 004d 0100 0000 0000  ....data.M......
```

- `RIFF` magic, size 85,284 + 8.
- `WAVE` format, fmt chunk: PCM (0x0001), mono (0x0001), 44100 Hz
  (0x0000AC44), 88200 bytes/s, block-align 2, 16 bits/sample.
- `data` chunk size 0x00014D00 = 85,248 bytes of PCM ≈ 42,624 i16
  samples — matches the reported frame count.

## Coverage matrix

| PoC plan exit criterion | Status | Evidence |
|---|---|---|
| Capture/playback works on at least one **desktop** target | PASS | `poc/audio-capture-playback-spike/VERIFICATION.md` |
| Capture/playback works on at least one **mobile** target | **PASS** | This document. |

## What this spike does NOT validate

- iOS (deferred per DEC-011.1; requires macOS + Xcode hardware).
- Android emulator audio path (skipped — physical device is
  stronger evidence).
- API 24–25 devices (cpal's OpenSL ES fallback path is not exercised
  here; only AAudio via API 26+).
- Bit-exact loopback signal integrity from capture to playback.
- Audio latency under load.
- Streaming reconfiguration on device change or audio focus loss.
- Background-service / foreground-service audio (required for a real
  voice client; out of scope here).
- DSP, Opus encode/decode, jitter buffer, mixer — owned by
  `chanora_audio`.
- Privacy-sensitive UX (microphone consent flows beyond a single
  runtime grant).

## Decisions closed by this spike

- **DEC-011.1** sub-decision is promoted from
  `Accepted (desktop) / Deferred (mobile)` to
  `Accepted (desktop: cpal; Android: cpal-on-Oboe) / Deferred (iOS)`.
  See `docs/governance/product-decision-register.md` v0.9.4.
- The audio row in
  `docs/architecture/proof-of-concept-plan.md` §2 is promoted from
  PARTIAL PASS to PASS.
- RISK-PoC-001 in `docs/governance/poc-results-summary.md` is closed
  for Android; iOS portion remains open.
