refactor(ding): synthesise on demand instead of vendoring the WAV

Move the ding renderer into pkg/service/ding so it can run both
at request time (from the new HandleDing handler) and offline
(from the existing scripts/gen-aftertouch-ding CLI, now a thin
wrapper around the same package).

- GET /media/aftertouch-ding.wav synthesises on first call,
  caches the default-options bytes via sync.Once, and accepts
  query-string overrides for every knob (pitch-{high,mid,low},
  chirp-ms, gap-ms, attack-ms, release-ms, sample-rate, peak).
  Invalid / out-of-range values silently fall back to defaults.
- Embedded WAV is gone from VCS — no 52 KB binary in the
  repo, and tweaking the sound is now a query-param away rather
  than a regenerate-and-commit cycle.
- Health-tab playback_test check is unchanged: the URL it
  references (/media/aftertouch-ding.wav) keeps the same shape,
  the handler just produces the bytes dynamically now.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Tobias Gesellchen
2026-05-19 23:20:40 +02:00
co-authored by Claude Opus 4.7
parent 6356ca588b
commit 147a69d1c3
8 changed files with 746 additions and 241 deletions
+33 -241
View File
@@ -1,273 +1,65 @@
// Generator for the AfterTouch "ding" sound — a two-chirp signature
// derived from the braille letters S and T (which the AfterTouch
// logo overlays).
//
// Mapping:
//
// Braille S = ⠎ = dots 2, 3, 4
// Braille T = ⠞ = dots 2, 3, 4, 5
//
// Dot positions in the 6-dot grid:
// 1 4
// 2 5
// 3 6
//
// Columns map to stereo channels:
// left column (1,2,3) → left channel
// right column (4,5,6) → right channel
//
// Rows map to pitch:
// top row (1,4) → A5 (880 Hz)
// mid row (2,5) → E5 (659.25 Hz)
// bottom row (3,6) → A4 (440 Hz)
//
// So:
//
// S (dots 2,3,4): L = E5+A4, R = A5
// T (dots 2,3,4,5): L = E5+A4, R = A5+E5 (S with an extra voice on the right)
//
// Total clip ≈ 600 ms: chirp(S) ~250 ms, gap ~100 ms, chirp(T) ~250 ms.
// Each chirp has a short attack and decay envelope to avoid clicks.
// Offline generator for the AfterTouch "ding" WAV. Thin CLI
// wrapper around pkg/service/ding so the same renderer used at
// runtime (HandleDing on GET /media/aftertouch-ding.wav) can
// also be invoked from the shell — handy for previewing parameter
// tweaks or producing a one-off file for sharing.
//
// Run:
//
// go run ./scripts/gen-aftertouch-ding > pkg/service/handlers/static/media/aftertouch-ding.wav
// go run ./scripts/gen-aftertouch-ding > ding.wav
// go run ./scripts/gen-aftertouch-ding -o ding.wav
// go run ./scripts/gen-aftertouch-ding -pitch-high 1200 -o ding.wav
//
// Or pass -o to write directly:
//
// go run ./scripts/gen-aftertouch-ding -o pkg/service/handlers/static/media/aftertouch-ding.wav
// All flags fall back to defaults defined in pkg/service/ding;
// pass only the knobs you want to override.
package main
import (
"bytes"
"encoding/binary"
"flag"
"fmt"
"io"
"math"
"os"
)
const (
sampleRate = 22050
channels = 2
bitsPer = 16
)
// Pitches (Hz).
const (
pitchHigh = 880.00 // A5 (top row)
pitchMid = 659.2551 // E5 (mid row)
pitchLow = 440.00 // A4 (bottom row)
)
// A "voice" is a single sine tone routed to one stereo channel.
type voice struct {
freq float64
channel int // 0 = left, 1 = right
}
// Active voices per braille letter, derived from the dot mapping above.
var (
voicesS = []voice{
{freq: pitchMid, channel: 0}, // dot 2: left-mid
{freq: pitchLow, channel: 0}, // dot 3: left-bottom
{freq: pitchHigh, channel: 1}, // dot 4: right-top
}
voicesT = []voice{
{freq: pitchMid, channel: 0}, // dot 2: left-mid
{freq: pitchLow, channel: 0}, // dot 3: left-bottom
{freq: pitchHigh, channel: 1}, // dot 4: right-top
{freq: pitchMid, channel: 1}, // dot 5: right-mid
}
"github.com/gesellix/bose-soundtouch/pkg/service/ding"
)
func main() {
var outPath string
flag.StringVar(&outPath, "o", "", "output WAV path; default stdout")
flag.Parse()
var (
chirpDur = 0.25 // seconds
gapDur = 0.10
attack = 0.020 // fade-in, avoids click
release = 0.060 // fade-out, avoids tail click
outPath string
opts ding.Options
)
chirpN := int(math.Round(float64(sampleRate) * chirpDur))
gapN := int(math.Round(float64(sampleRate) * gapDur))
flag.StringVar(&outPath, "o", "", "output WAV path; default stdout")
// Allocate exactly: two chirps + one gap. Doing this from the
// rendered sample counts (instead of re-computing from seconds)
// avoids a rounding off-by-one between the two paths.
samplesPerChannel := chirpN*2 + gapN
left := make([]float64, samplesPerChannel)
right := make([]float64, samplesPerChannel)
flag.IntVar(&opts.SampleRate, "sample-rate", 0, "Hz; 0 → default 22050")
flag.Float64Var(&opts.PitchHigh, "pitch-high", 0, "Hz, top row; 0 → default 880 (A5)")
flag.Float64Var(&opts.PitchMid, "pitch-mid", 0, "Hz, mid row; 0 → default 659.25 (E5)")
flag.Float64Var(&opts.PitchLow, "pitch-low", 0, "Hz, bottom row; 0 → default 440 (A4)")
flag.Float64Var(&opts.ChirpDuration, "chirp-sec", 0, "chirp duration; 0 → default 0.25")
flag.Float64Var(&opts.GapDuration, "gap-sec", 0, "between-chirp gap; 0 → default 0.10")
flag.Float64Var(&opts.AttackDuration, "attack-sec", 0, "fade-in; 0 → default 0.020")
flag.Float64Var(&opts.ReleaseDuration, "release-sec", 0, "fade-out; 0 → default 0.060")
flag.Float64Var(&opts.Peak, "peak", 0, "0..1 headroom; 0 → default 0.85")
renderChirp(left, right, 0, chirpN, voicesS, attack, release)
renderChirp(left, right, chirpN+gapN, chirpN, voicesT, attack, release)
flag.Parse()
normalise(left, right, 0.85) // headroom below 1.0 to avoid clipping
var buf bytes.Buffer
if err := writeWAV(&buf, left, right); err != nil {
fail("encode: %v", err)
}
data := ding.Render(opts)
var w io.Writer = os.Stdout
if outPath != "" {
f, err := os.Create(outPath)
if err != nil {
fail("create %s: %v", outPath, err)
fmt.Fprintf(os.Stderr, "gen-aftertouch-ding: create %s: %v\n", outPath, err)
os.Exit(1)
}
defer f.Close()
defer func() { _ = f.Close() }()
w = f
}
if _, err := w.Write(buf.Bytes()); err != nil {
fail("write: %v", err)
if _, err := w.Write(data); err != nil {
fmt.Fprintf(os.Stderr, "gen-aftertouch-ding: write: %v\n", err)
os.Exit(1)
}
}
// renderChirp writes one chirp into the L/R buffers starting at offset.
// The envelope is a trapezoid: linear attack, flat sustain, linear release.
func renderChirp(left, right []float64, offset, length int, voices []voice, attackSec, releaseSec float64) {
attackN := int(math.Round(float64(sampleRate) * attackSec))
releaseN := int(math.Round(float64(sampleRate) * releaseSec))
if attackN+releaseN > length {
attackN = length / 3
releaseN = length / 3
}
for i := 0; i < length; i++ {
t := float64(i) / float64(sampleRate)
env := 1.0
switch {
case i < attackN:
env = float64(i) / float64(attackN)
case i >= length-releaseN:
remaining := length - i
env = float64(remaining) / float64(releaseN)
}
for _, v := range voices {
sample := math.Sin(2 * math.Pi * v.freq * t) * env
if v.channel == 0 {
left[offset+i] += sample
} else {
right[offset+i] += sample
}
}
}
}
// normalise scales L/R so the peak absolute value equals `peak` (≤ 1.0).
// This keeps the chord-sum from clipping without hardcoding voice counts.
func normalise(left, right []float64, peak float64) {
maxVal := 0.0
for i := range left {
if v := math.Abs(left[i]); v > maxVal {
maxVal = v
}
if v := math.Abs(right[i]); v > maxVal {
maxVal = v
}
}
if maxVal == 0 {
return
}
scale := peak / maxVal
for i := range left {
left[i] *= scale
right[i] *= scale
}
}
func writeWAV(w io.Writer, left, right []float64) error {
if len(left) != len(right) {
return fmt.Errorf("channel length mismatch: %d vs %d", len(left), len(right))
}
samples := len(left)
dataBytes := samples * channels * (bitsPer / 8)
totalRIFFSize := 4 + (8 + 16) + (8 + dataBytes) // "WAVE" + fmt chunk + data chunk
// RIFF header
if _, err := w.Write([]byte("RIFF")); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint32(totalRIFFSize)); err != nil {
return err
}
if _, err := w.Write([]byte("WAVE")); err != nil {
return err
}
// fmt chunk
if _, err := w.Write([]byte("fmt ")); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint32(16)); err != nil { // PCM fmt chunk size
return err
}
if err := binary.Write(w, binary.LittleEndian, uint16(1)); err != nil { // PCM
return err
}
if err := binary.Write(w, binary.LittleEndian, uint16(channels)); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint32(sampleRate)); err != nil {
return err
}
byteRate := uint32(sampleRate * channels * (bitsPer / 8))
if err := binary.Write(w, binary.LittleEndian, byteRate); err != nil {
return err
}
blockAlign := uint16(channels * (bitsPer / 8))
if err := binary.Write(w, binary.LittleEndian, blockAlign); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint16(bitsPer)); err != nil {
return err
}
// data chunk
if _, err := w.Write([]byte("data")); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint32(dataBytes)); err != nil {
return err
}
for i := 0; i < samples; i++ {
l := floatToInt16(left[i])
r := floatToInt16(right[i])
if err := binary.Write(w, binary.LittleEndian, l); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, r); err != nil {
return err
}
}
return nil
}
func floatToInt16(v float64) int16 {
if v > 1.0 {
v = 1.0
} else if v < -1.0 {
v = -1.0
}
return int16(math.Round(v * 32767))
}
func fail(format string, args ...any) {
fmt.Fprintf(os.Stderr, "gen-aftertouch-ding: "+format+"\n", args...)
os.Exit(1)
}