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third_party/sendspin-go/pkg/audio/encode/opus.go

@@ -0,0 +1,64 @@
+// ABOUTME: Opus audio encoder
+// ABOUTME: Encodes int32 samples to Opus bytes
+package encode
+
+import (
+	"fmt"
+
+	"github.com/Sendspin/sendspin-go/pkg/audio"
+	"gopkg.in/hraban/opus.v2"
+)
+
+type OpusEncoder struct {
+	encoder    *opus.Encoder
+	sampleRate int
+	channels   int
+	frameSize  int
+	pcmBuf     []int16 // reusable conversion buffer
+	outBuf     []byte  // reusable encode output buffer
+}
+
+func NewOpus(format audio.Format) (Encoder, error) {
+	if format.Codec != "opus" {
+		return nil, fmt.Errorf("invalid codec for Opus encoder: %s", format.Codec)
+	}
+
+	encoder, err := opus.NewEncoder(format.SampleRate, format.Channels, opus.AppAudio)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create opus encoder: %w", err)
+	}
+
+	// Opus frame size depends on sample rate
+	frameSize := format.SampleRate / 50 // 20ms frame
+
+	return &OpusEncoder{
+		encoder:    encoder,
+		sampleRate: format.SampleRate,
+		channels:   format.Channels,
+		frameSize:  frameSize,
+		pcmBuf:     make([]int16, frameSize*format.Channels),
+		outBuf:     make([]byte, 4000),
+	}, nil
+}
+
+func (e *OpusEncoder) Encode(samples []int32) ([]byte, error) {
+	if len(samples) > len(e.pcmBuf) {
+		e.pcmBuf = make([]int16, len(samples))
+	}
+
+	pcm := e.pcmBuf[:len(samples)]
+	for i, sample := range samples {
+		pcm[i] = audio.SampleToInt16(sample)
+	}
+
+	n, err := e.encoder.Encode(pcm, e.outBuf)
+	if err != nil {
+		return nil, fmt.Errorf("opus encode error: %w", err)
+	}
+
+	return append([]byte(nil), e.outBuf[:n]...), nil
+}
+
+func (e *OpusEncoder) Close() error {
+	return nil
+}