13 KiB
13 KiB
phase, verified, status, score, re_verification
| phase | verified | status | score | re_verification |
|---|---|---|---|---|
| 02-audio-synthesis-engine | 2026-03-26T00:00:00Z | passed | 9/9 must-haves verified | false |
Phase 2: Audio Synthesis Engine — Verification Report
Phase Goal: Synthesize audio from classified traffic — oscillator bank, mixer, MP3 encoder Verified: 2026-03-26 Status: PASSED Re-verification: No — initial verification
Goal Achievement
Observable Truths
All must-haves drawn from PLAN frontmatter across all three plans (02-01, 02-02, 02-03).
| # | Truth | Status | Evidence |
|---|---|---|---|
| 1 | Each of 11 traffic classes has a unique frequency, harmonic profile, and pan position defined | VERIFIED | ClassFreqConfigs in synth/config.go lines 30-44; all 11 classes present, frequencies 65-780 Hz; TestFrequenciesUnique + TestAllClassesHaveConfig pass |
| 2 | Phase-accumulator oscillator produces non-zero PCM samples with harmonics | VERIFIED | Oscillator.Advance() in synth/oscillator.go sums weighted sine partials; TestOscillatorAdvance + TestOscillatorDistinctFreqs pass |
| 3 | EMA amplitude smoothing moves current amplitude toward target over time | VERIFIED | Layer.AdvanceSample() in synth/layer.go applies currentAmp += alpha*(target-current); TestEMAAmplitudeRise + TestEMAAmplitudeDecay pass |
| 4 | Whisper floor prevents amplitude from reaching zero once a class has been seen | VERIFIED | UpdateTarget in synth/layer.go line 46 enforces whisper + (1.0-whisper)*normalizedRate; TestWhisperFloor pass |
| 5 | go-lame v0.0.9 is in go.mod and CGo build succeeds | VERIFIED | go.mod contains github.com/sjzar/go-lame v0.0.9 as direct dependency; CGO_ENABLED=1 go build ./... exits 0 |
| 6 | OscillatorBank updates all 11 layers from a WindowSnapshot and renders stereo PCM frames | VERIFIED | OscillatorBank.RenderWindow in synth/bank.go; TestNewBankHas11Layers + TestRenderWindowOutputLength + TestRenderWindowNonZeroWithTraffic pass |
| 7 | Mixer sums 11 layers with fixed 1/11 gain per layer — peak sum never exceeds 1.0 | VERIFIED | GainPerLayer applied in bank.go lines 52-53; TestMixerNoClip verifies over 10 windows |
| 8 | Stereo panning uses constant-power pan law producing distinct L/R values for non-center sources | VERIFIED | PanGains in synth/mixer.go uses cos/sin mapping; TestPanGainsPowerPreserved + TestStereoPan pass |
| 9 | Synthetic WindowSnapshots produce a valid MP3 file that passes ffprobe validation | VERIFIED | TestMP3Valid and TestEncodeMP3DirectBytes in encode/mp3_test.go both pass with ffprobe validation |
| 10 | Zero-packet input produces a clear error message and no file on disk | VERIFIED | if totalPackets == 0 guard in encode/mp3.go line 52 before os.Create; TestZeroPacketError passes confirming no file created |
| 11 | User can specify -o flag for output path; default includes timestamp | VERIFIED | StringVarP(&outputPath, "output", "o", ...) in main.go line 38; netsynth-%s.mp3 timestamp default line 53; --help output confirms flag |
| 12 | MP3 is encoded at 44100 Hz, 128 kbps, stereo via go-lame | VERIFIED | encode/mp3.go: SetInSamplerate(44100), SetBitrate(128), SetNumChannels(2); ffprobe validates output |
Score: 12/12 truths verified (9 distinct must_haves across plans, all with sub-components verified)
Required Artifacts
| Artifact | Provides | Lines | Status | Details |
|---|---|---|---|---|
synth/config.go |
FreqConfig, HarmonicDef types; ClassFreqConfigs table for 11 classes | 44 | VERIFIED | Contains ClassFreqConfigs, WhisperFloor=0.03, SampleRate=44100, GainPerLayer |
synth/oscillator.go |
Phase-accumulator oscillator with Advance method | 38 | VERIFIED | Contains func (o *Oscillator) Advance(harmonics []HarmonicDef) float64; uses subtraction wrap not math.Mod |
synth/layer.go |
Layer struct with EMA amplitude, whisper floor, target updates | 70 | VERIFIED | Contains UpdateTarget, AdvanceSample, l.whisper + (1.0-l.whisper)*normalizedRate |
synth/config_test.go |
Config table tests | 50 | VERIFIED | Contains TestAllClassesHaveConfig, TestFrequenciesInRange, TestFrequenciesUnique, TestHarmonicsNonEmpty, TestPanPositionsInRange |
synth/oscillator_test.go |
Oscillator behavioral tests | 59 | VERIFIED | Contains TestOscillatorAdvance, TestOscillatorPhaseWrap, TestOscillatorDistinctFreqs |
synth/layer_test.go |
Layer EMA and whisper floor tests | 88 | VERIFIED | Contains TestEMAAmplitudeRise, TestEMAAmplitudeDecay, TestWhisperFloor, TestWhisperFloorNotSeenIsZero |
synth/mixer.go |
panGains constant-power function; float64-to-int16 conversion | 40 | VERIFIED | Contains func PanGains, func StereoFramesToInt16Bytes, math.Cos(angle), math.Sin(angle), func clamp |
synth/mixer_test.go |
Pan law and PCM conversion tests | 96 | VERIFIED | Contains TestPanGainsCenter, TestStereoFramesToInt16Bytes, TestClampPreventsOverflow |
synth/bank.go |
OscillatorBank with NewBank, RenderWindow methods | 58 | VERIFIED | Contains func NewBank, func (b *OscillatorBank) RenderWindow, GainPerLayer, imports classify |
synth/bank_test.go |
Bank rendering and mixing tests | 160 | VERIFIED | Contains TestMixerNoClip, TestStereoPan, TestRenderWindowOutputLength, TestNewBankHas11Layers |
encode/mp3.go |
EncodeMP3 function and RunSynthesis orchestrator | 66 | VERIFIED | Contains func EncodeMP3, func RunSynthesis, InitParams() after Set*, zero-packet guard before os.Create |
encode/mp3_test.go |
Integration test with ffprobe validation; zero-packet guard test | 182 | VERIFIED | Contains TestMP3Valid, TestZeroPacketError, TestEncodeMP3DirectBytes; uses ffprobe |
cmd/netsynth/main.go |
-o flag wiring with timestamp default; snapshot accumulator | 132 | VERIFIED | Contains outputPath, StringVarP, netsynth-%s.mp3, collectedSnapshots, TODO(phase-3) |
Key Link Verification
| From | To | Via | Status | Details |
|---|---|---|---|---|
| synth/config.go | classify/types.go | map[classify.TrafficClass]FreqConfig |
WIRED | Line 30: var ClassFreqConfigs = map[classify.TrafficClass]FreqConfig{ |
| synth/layer.go | synth/oscillator.go | Layer embeds Oscillator | WIRED | Layer.Osc field is *Oscillator; AdvanceSample calls l.Osc.Advance |
| synth/bank.go | synth/layer.go | Bank holds map[classify.TrafficClass]*Layer |
WIRED | Line 8: layers map[classify.TrafficClass]*Layer; NewBank creates layers |
| synth/bank.go | synth/config.go | Reads ClassFreqConfigs to initialize layers | WIRED | Line 20: cfg := ClassFreqConfigs[class] |
| synth/mixer.go | synth/bank.go | StereoFramesToInt16Bytes converts bank output | WIRED | encode/mp3.go line 32 calls synth.StereoFramesToInt16Bytes(frames) where frames come from bank.RenderWindow |
| encode/mp3.go | synth/bank.go | RunSynthesis calls bank.RenderWindow per snapshot | WIRED | Lines 57-60: bank := synth.NewBank(1.0) then frames := bank.RenderWindow(snap) |
| encode/mp3.go | synth/mixer.go | Uses StereoFramesToInt16Bytes for PCM conversion | WIRED | Line 32: pcmBytes := synth.StereoFramesToInt16Bytes(frames) |
| cmd/netsynth/main.go | encode/mp3.go | -o flag wired; RunSynthesis integration deferred to Phase 3 | PARTIAL (by design) | outputPath defined and populated; TODO(phase-3) marks deferred integration point per plan spec |
Note: The cmd/netsynth/main.go -> encode/mp3.go link is PARTIAL by deliberate design. Plan 02-03 explicitly states "Do NOT import the encode package yet — Phase 3 handles that." This is not a gap.
Data-Flow Trace (Level 4)
The phase produces a file-output pipeline (not a UI component), so data-flow tracing focuses on the end-to-end synthesis chain.
| Artifact | Data Variable | Source | Produces Real Data | Status |
|---|---|---|---|---|
| encode/mp3.go | allFrames [][2]float64 |
bank.RenderWindow(snap) for each snapshot |
Yes — renders 22050 stereo PCM frames per snapshot via OscillatorBank | FLOWING |
| encode/mp3.go | pcmBytes []byte |
synth.StereoFramesToInt16Bytes(allFrames) |
Yes — interleaved int16 LE bytes from float64 frames | FLOWING |
| encode/mp3.go (go-lame) | MP3 file | wr.Write(pcmBytes) + wr.Close() |
Yes — ffprobe validates real MP3 output in tests | FLOWING |
| synth/bank.go | frames [][2]float64 |
11 layers each calling AdvanceSample() with EMA-smoothed oscillators |
Yes — non-zero samples when traffic seen; verified by TestRenderWindowNonZeroWithTraffic | FLOWING |
Behavioral Spot-Checks
| Behavior | Command | Result | Status |
|---|---|---|---|
| All synth package tests pass | CGO_ENABLED=1 go test ./synth/... -count=1 |
ok github.com/netsynth/netsynth/synth 0.681s |
PASS |
| All encode package tests pass (including ffprobe MP3 validation) | CGO_ENABLED=1 go test ./encode/... -count=1 |
ok github.com/netsynth/netsynth/encode 0.307s |
PASS |
| CLI builds and -o flag visible in help | go run ./cmd/netsynth/ --help | grep -E "\-o.*output" |
-o, --output string Output MP3 file path (default: netsynth-<timestamp>.mp3) |
PASS |
| Full CGo build succeeds | CGO_ENABLED=1 go build ./... |
Exits 0, no errors | PASS |
| Full test suite (all packages) passes | CGO_ENABLED=1 go test ./... |
All 6 packages pass | PASS |
29 tests pass across synth and encode packages.
Requirements Coverage
| Requirement | Source Plan | Description | Status | Evidence |
|---|---|---|---|---|
| SYNTH-01 | 02-01 | Each traffic class generates a distinct ambient/drone layer (layered sine/harmonic waves) | SATISFIED | ClassFreqConfigs has 11 distinct entries; FreqConfig carries BaseHz, Harmonics, Pan; oscillator renders additive harmonics via Advance() |
| SYNTH-02 | 02-01 | Drone layer amplitudes evolve over time windows based on traffic volume per class | SATISFIED | Layer.UpdateTarget(count, maxCount) scales amplitude by normalized rate; EMA smoothing in AdvanceSample(); whisper floor maintains presence; TestEMAAmplitudeRise + TestMultipleWindowsEMAConvergence verify |
| SYNTH-03 | 02-02 | Multiple drone layers are mixed into a single coherent audio stream without distortion | SATISFIED | Fixed GainPerLayer (1/11) applied per layer in RenderWindow; constant-power panning; TestMixerNoClip verifies 11 max-amplitude layers produce no frame with |L| or |R| > 1.0 |
| OUT-01 | 02-03 | User can specify output file path via -o flag (defaults to netsynth-<timestamp>.mp3) |
SATISFIED | StringVarP(&outputPath, "output", "o", ...) in main.go; timestamp default netsynth-20060102-150405.mp3; visible in --help |
| OUT-02 | 02-03 | Output is encoded as a valid MP3 file | SATISFIED | EncodeMP3 uses go-lame at 44100 Hz, 128 kbps, stereo; TestMP3Valid + TestEncodeMP3DirectBytes use ffprobe to validate MP3 format |
| OUT-03 | 02-03 | Empty captures (zero packets) produce a clear error instead of a corrupt file | SATISFIED | totalPackets == 0 check in RunSynthesis before os.Create; returns error "no packets captured: output MP3 not written"; TestZeroPacketError verifies no file on disk |
All 6 requirements declared across the three plans are satisfied. No orphaned requirements found — REQUIREMENTS.md maps all 6 IDs to Phase 2, all 6 are covered.
Anti-Patterns Found
| File | Line | Pattern | Severity | Impact |
|---|---|---|---|---|
| cmd/netsynth/main.go | 99 | TODO(phase-3): Pass collectedSnapshots to encode.RunSynthesis(...) |
Info | Expected deferred wiring; plan explicitly defers encode integration to Phase 3. Not a blocker — outputPath and collectedSnapshots are both populated and ready. |
No blockers. No stub implementations. No placeholder data. No empty return values in production code paths.
Note on go.mod: github.com/sjzar/go-lame was listed as // indirect prior to verification but encode/mp3.go imports it directly. Running go mod tidy during verification corrected this — the dependency is now properly marked as direct in go.mod. Build and tests were unaffected throughout.
Human Verification Required
None required. All phase-2 behaviors are verifiable programmatically:
- Audio quality (timbre, harmonic distinctness) will be evaluable in Phase 3 when live traffic synthesis is complete. Phase 2's contract is correct PCM generation and valid MP3 encoding, both of which are verified via ffprobe.
- The -o flag produces the correct timestamp format; its integration into the live pipeline (Phase 3) is the appropriate point for end-to-end UX testing.
Gaps Summary
No gaps. All must-haves from the three plans are verified at all levels:
- Level 1 (exists): All 13 artifact files are present
- Level 2 (substantive): All files contain required functions, patterns, and implementations
- Level 3 (wired): All key links are connected; the one deferred link (main.go -> encode) is intentional per plan spec
- Level 4 (data flowing): The full synthesis pipeline WindowSnapshot -> OscillatorBank -> stereo PCM -> MP3 is traced end-to-end; ffprobe validates real output
The phase goal is achieved.
Verified: 2026-03-26 Verifier: Claude (gsd-verifier)