refactor: extract flag parsing, validation, and packet processing into functions; add README and .gitignore

caption.go

@@ -0,0 +1,154 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"strings"
+	"time"
+
+	sherpa "github.com/k2-fsa/sherpa-onnx-go-linux"
+)
+
+type captionProcessor struct {
+	cfg        settings
+	recognizer *sherpa.OfflineRecognizer
+	vad        *sherpa.VoiceActivityDetector
+	output     io.Writer
+
+	fixedSamples   []float32
+	previewSamples []float32
+	previewActive  bool
+	previewVisible bool
+	nextPreviewAt  int
+	totalSamples   int
+}
+
+func newCaptionProcessor(cfg settings, recognizer *sherpa.OfflineRecognizer, vad *sherpa.VoiceActivityDetector, output io.Writer) *captionProcessor {
+	return &captionProcessor{
+		cfg:           cfg,
+		recognizer:    recognizer,
+		vad:           vad,
+		output:        output,
+		nextPreviewAt: durationSamples(cfg.chunkDuration),
+	}
+}
+
+func (p *captionProcessor) accept(samples []float32) {
+	if len(samples) == 0 {
+		return
+	}
+	if p.cfg.mode == "fixed" {
+		p.acceptFixed(samples)
+		return
+	}
+	p.acceptVAD(samples)
+}
+
+func (p *captionProcessor) acceptFixed(samples []float32) {
+	p.fixedSamples = append(p.fixedSamples, samples...)
+	chunkSize := durationSamples(p.cfg.chunkDuration)
+	for len(p.fixedSamples) >= chunkSize {
+		p.emitCommitted(p.totalSamples, p.totalSamples+chunkSize, p.fixedSamples[:chunkSize])
+		p.fixedSamples = p.fixedSamples[chunkSize:]
+		p.totalSamples += chunkSize
+	}
+}
+
+func (p *captionProcessor) acceptVAD(samples []float32) {
+	p.totalSamples += len(samples)
+	p.vad.AcceptWaveform(samples)
+
+	if p.previewActive || rmsDBFS(samples) >= p.cfg.previewThresholdDB {
+		p.previewActive = true
+		p.previewSamples = append(p.previewSamples, samples...)
+		if len(p.previewSamples) >= p.nextPreviewAt {
+			p.emitPreview(p.previewSamples)
+			p.nextPreviewAt += durationSamples(p.cfg.chunkDuration)
+		}
+	}
+	p.drainVAD()
+}
+
+func (p *captionProcessor) drainVAD() {
+	for !p.vad.IsEmpty() {
+		segment := p.vad.Front()
+		p.vad.Pop()
+		p.clearPreview()
+		p.emitCommitted(segment.Start, segment.Start+len(segment.Samples), segment.Samples)
+		p.previewSamples = nil
+		p.previewActive = false
+		p.nextPreviewAt = durationSamples(p.cfg.chunkDuration)
+	}
+}
+
+func (p *captionProcessor) flush() {
+	if p.cfg.mode == "fixed" {
+		if len(p.fixedSamples) > 0 {
+			p.emitCommitted(p.totalSamples, p.totalSamples+len(p.fixedSamples), p.fixedSamples)
+		}
+		return
+	}
+	p.vad.Flush()
+	p.drainVAD()
+	p.clearPreview()
+}
+
+func (p *captionProcessor) emitPreview(samples []float32) {
+	text := p.decode(samples)
+	if text == "" {
+		return
+	}
+	fmt.Fprintf(p.output, "\r\033[2K… %s", text)
+	p.previewVisible = true
+}
+
+func (p *captionProcessor) emitCommitted(start, end int, samples []float32) {
+	text := p.decode(samples)
+	if text == "" {
+		return
+	}
+	p.clearPreview()
+	fmt.Fprintf(p.output, "[%s-%s] %s\n", formatAudioTime(start), formatAudioTime(end), text)
+}
+
+func (p *captionProcessor) clearPreview() {
+	if p.previewVisible {
+		fmt.Fprint(p.output, "\r\033[2K")
+		p.previewVisible = false
+	}
+}
+
+func (p *captionProcessor) decode(samples []float32) string {
+	if len(samples) == 0 {
+		return ""
+	}
+	stream := sherpa.NewOfflineStream(p.recognizer)
+	defer sherpa.DeleteOfflineStream(stream)
+	stream.AcceptWaveform(sampleRate, samples)
+	p.recognizer.Decode(stream)
+	return strings.TrimSpace(stream.GetResult().Text)
+}
+
+func durationSamples(duration time.Duration) int {
+	return int(duration * sampleRate / time.Second)
+}
+
+func rmsDBFS(samples []float32) float64 {
+	if len(samples) == 0 {
+		return math.Inf(-1)
+	}
+	var sum float64
+	for _, sample := range samples {
+		sum += float64(sample * sample)
+	}
+	rms := math.Sqrt(sum / float64(len(samples)))
+	if rms == 0 {
+		return math.Inf(-1)
+	}
+	return 20 * math.Log10(rms)
+}
+
+func formatAudioTime(samples int) string {
+	return fmt.Sprintf("%.2fs", float64(samples)/sampleRate)
+}