feat(capability): 转码能力包（vendor 纯 Go AMR-NB 解码器 + 黄金向量逐样本对照 + 8 哨兵 + 注册面）

internal/capability/transcode/amrnb/amrnb.go

@@ -0,0 +1,103 @@
+package amrnb
+
+import "errors"
+
+// Encoder encodes 8 kHz mono PCM into AMR-NB RFC 4867 RTP payloads.
+//
+// It satisfies the codec.Encoder interface: Encode takes one 20 ms frame
+// (160 int16 samples) and returns a complete RTP payload (CMR + ToC + speech
+// bits) in the configured payload format.
+type Encoder struct {
+	mode         Mode
+	octetAligned bool
+	st           encoderState
+}
+
+// EncoderConfig configures a new AMR-NB encoder.
+type EncoderConfig struct {
+	Mode         Mode // active speech mode (0..7)
+	OctetAligned bool // true: octet-aligned framing; false: bandwidth-efficient
+}
+
+// NewEncoder creates an AMR-NB encoder for the given mode and payload format.
+func NewEncoder(cfg EncoderConfig) (*Encoder, error) {
+	if !cfg.Mode.Valid() {
+		return nil, errors.New("amrnb: invalid encoder mode")
+	}
+	e := &Encoder{mode: cfg.Mode, octetAligned: cfg.OctetAligned}
+	e.st.reset()
+	return e, nil
+}
+
+// Encode encodes one 20 ms frame (160 samples) into an RTP payload.
+func (e *Encoder) Encode(samples []int16) ([]byte, error) {
+	if len(samples) != FrameSamples {
+		return nil, errors.New("amrnb: encode expects exactly 160 samples")
+	}
+	bits, err := e.st.encodeFrame(e.mode, samples)
+	if err != nil {
+		return nil, err
+	}
+	f := frame{ft: e.mode.FrameType(), q: true, data: bits}
+	if e.octetAligned {
+		return packPayloadOctet(noCMR, []frame{f}), nil
+	}
+	return packPayloadBandwidthEfficient(noCMR, []frame{f}), nil
+}
+
+// SetMode changes the active speech mode (e.g. in response to a peer CMR).
+func (e *Encoder) SetMode(m Mode) {
+	if m.Valid() {
+		e.mode = m
+	}
+}
+
+// Reset clears all encoder state.
+func (e *Encoder) Reset() { e.st.reset() }
+
+// Decoder decodes AMR-NB RFC 4867 RTP payloads into 8 kHz mono PCM.
+type Decoder struct {
+	octetAligned bool
+	st           decoderState
+}
+
+// DecoderConfig configures a new AMR-NB decoder.
+type DecoderConfig struct {
+	OctetAligned bool // must match the negotiated payload format
+}
+
+// NewDecoder creates an AMR-NB decoder for the given payload format.
+func NewDecoder(cfg DecoderConfig) *Decoder {
+	d := &Decoder{octetAligned: cfg.OctetAligned}
+	d.st.reset()
+	return d
+}
+
+// Decode decodes one RTP payload, returning concatenated PCM for all frames it
+// carries (one 160-sample frame per speech/SID/no-data ToC entry).
+func (d *Decoder) Decode(payload []byte) ([]int16, error) {
+	var (
+		frames []frame
+		err    error
+	)
+	if d.octetAligned {
+		_, frames, err = unpackPayloadOctet(payload)
+	} else {
+		_, frames, err = unpackPayloadBandwidthEfficient(payload)
+	}
+	if err != nil {
+		return nil, err
+	}
+	out := make([]int16, 0, len(frames)*FrameSamples)
+	for _, f := range frames {
+		pcm, derr := d.st.decodeFrame(f)
+		if derr != nil {
+			return nil, derr
+		}
+		out = append(out, pcm...)
+	}
+	return out, nil
+}
+
+// Reset clears all decoder state.
+func (d *Decoder) Reset() { d.st.reset() }