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/dsp_enc_cb8.go

@@ -0,0 +1,125 @@
+package amrnb
+
+// 8-pulse algebraic codebook search (31 bits, MR102), ported from opencore-amrnb
+// c8_31pf.cpp. Drives search10and8i40 (8 pulses, step 4), then builds the
+// codeword and compresses the eight pulse positions / four track signs into the
+// 7-value transmitted index. The exact encoder counterpart of dec8i40_31bits
+// (decompressCode). Bit-exact with the reference.
+
+// build8Code assembles the 8-pulse innovation cod and filtered code y, and the
+// linear track signs / pulse positions (with the same-track ordering/swap logic
+// that decompressCode inverts). Mirrors build_code (c8_31pf.cpp).
+func build8Code(codvec, sign, cod, h, y []int16) (signIndx [4]int16, posIndx [8]int16) {
+	const L = cL_CODE
+	for i := 0; i < L; i++ {
+		cod[i] = 0
+	}
+	for t := 0; t < 4; t++ {
+		posIndx[t] = -1
+		signIndx[t] = -1
+	}
+
+	var sgn [8]int16
+	for k := 0; k < 8; k++ {
+		i := codvec[k]
+		j := sign[i]
+		posIndex := i >> 2
+		track := i & 3
+
+		var signIndex int16
+		if j > 0 {
+			cod[i] = cod[i] + 8191
+			sgn[k] = 32767
+			signIndex = 0
+		} else {
+			cod[i] = cod[i] - 8191
+			sgn[k] = -32768
+			signIndex = 1
+		}
+
+		if posIndx[track] < 0 {
+			posIndx[track] = posIndex
+			signIndx[track] = signIndex
+		} else if (signIndex^signIndx[track])&1 == 0 {
+			if posIndx[track] <= posIndex {
+				posIndx[track+4] = posIndex
+			} else {
+				posIndx[track+4] = posIndx[track]
+				posIndx[track] = posIndex
+				signIndx[track] = signIndex
+			}
+		} else {
+			if posIndx[track] <= posIndex {
+				posIndx[track+4] = posIndx[track]
+				posIndx[track] = posIndex
+				signIndx[track] = signIndex
+			} else {
+				posIndx[track+4] = posIndex
+			}
+		}
+	}
+
+	for i := 0; i < L; i++ {
+		var s int32
+		for k := 0; k < 8; k++ {
+			ci := int(codvec[k])
+			if i-ci >= 0 {
+				s = L_mac(s, h[i-ci], sgn[k])
+			}
+		}
+		y[i] = round_(s)
+	}
+	return signIndx, posIndx
+}
+
+// compress10 packs three position indices into one 10-bit value. Mirrors
+// compress10 (the inverse of decompress10).
+func compress10(A, B, C int16) int16 {
+	ia := A >> 1
+	ib := (B >> 1) * 5
+	ic := (C >> 1) * 25
+	indx := (ib + ic + ia) << 3
+	indx += ((B & 1) << 1) + ((C & 1) << 2) + (A & 1)
+	return indx
+}
+
+// compressCode packs the four track signs and eight pulse positions into the
+// seven transmitted index values. Mirrors compress_code.
+func compressCode(signIndx, posIndx, indx []int16) {
+	for i := 0; i < 4; i++ {
+		indx[i] = signIndx[i]
+	}
+	indx[4] = compress10(posIndx[0], posIndx[4], posIndx[1])
+	indx[5] = compress10(posIndx[2], posIndx[6], posIndx[5])
+
+	ib := (posIndx[7] >> 1) & 1
+	ia := posIndx[3] >> 1
+	if ib == 1 {
+		ia = 4 - ia
+	}
+	ib = (posIndx[7] >> 1) * 5
+	ib += ia
+	ib <<= 5
+	ib += 12
+	ic := int16((int32(ib) * 1311) >> 15)
+	ic <<= 2
+	ia = posIndx[3] & 1
+	ib = (posIndx[7] & 1) << 1
+	indx[6] = ib + ic + ia
+}
+
+// code8i40_31bits runs the full MR102 8-pulse search, writing the innovation
+// cod, filtered code y, and the 7-value index. Mirrors code_8i40_31bits.
+func code8i40_31bits(x, cn, h, cod, y, indx []int16) {
+	var dn, sign [cL_CODE]int16
+	var rr [cL_CODE * cL_CODE]int16
+	var ipos, codvec [8]int16
+	var posMax [4]int16
+
+	corHX2(h, x, dn[:], 2, 4, 4)
+	setSign12k2(dn[:], cn, sign[:], posMax[:], 4, ipos[:], 4)
+	corH(h, sign[:], rr[:])
+	search10and8i40(8, 4, 4, dn[:], rr[:], ipos[:], posMax[:], codvec[:])
+	signIndx, posIndx := build8Code(codvec[:], sign[:], cod, h, y)
+	compressCode(signIndx[:], posIndx[:], indx)
+}