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_cbsearch2.go

@@ -0,0 +1,106 @@
+package amrnb
+
+// Parameterized codebook-search correlation, ported from opencore-amrnb
+// cor_h_x2.cpp. corHX2 is the generalized form of corHX used by the multi-pulse
+// searches (MR102: 4 tracks, MR122: 5 tracks): dn[i] = normalized 2·Σ x[j]·h[j-i]
+// with a configurable track count and step. Bit-exact with the reference.
+
+const cLOG2_OF_32 = 5
+
+// corHX2 computes the normalized target↔impulse correlation dn[] over nbTrack
+// tracks with the given step, scaled by sf. Mirrors cor_h_x2.
+func corHX2(h, x, dn []int16, sf, nbTrack, step int16) {
+	// y32[i] = 2·sum_{j=i}^{L-1} x[j]·h[j-i] = 2·sum_{j'=0}^{L-1-i} x[i+j']·h[j'].
+	// Zero-padding x past L turns this into one L-tap FIR over the padded input
+	// (firRaw); s<<1 == dst[i]<<1 holds mod 2^32 since <<1 distributes over the
+	// wrapping sum.
+	var xpad [2 * cL_CODE]int16
+	copy(xpad[:cL_CODE], x[:cL_CODE])
+	var dst [cL_CODE]int32
+	firRaw(dst[:], xpad[:], h[:cL_CODE])
+
+	var y32 [cL_CODE]int32
+	for i := 0; i < cL_CODE; i++ {
+		y32[i] = dst[i] << 1
+	}
+
+	tot := int32(cLOG2_OF_32)
+	for k := int16(0); k < nbTrack; k++ {
+		var max int32
+		for i := k; i < cL_CODE; i += step {
+			if a := L_abs(y32[i]); a > max {
+				max = a
+			}
+		}
+		tot += max >> 1
+	}
+
+	j := norm_l(tot) - sf
+	for i := 0; i < cL_CODE; i++ {
+		dn[i] = round_(L_shl(y32[i], j))
+	}
+}
+
+// setSign12k2 combines the residual cn and the correlation dn to determine each
+// position's pulse sign, the per-track maximum positions (posMax), and a cyclic
+// pulse-track ordering (ipos, length 2*nbTrack) starting from the strongest
+// track — the prep for the multi-pulse search_10and8i40. dn is updated in place
+// (negated where the combined sign is negative). Mirrors set_sign12k2.
+func setSign12k2(dn, cn, sign, posMax []int16, nbTrack int16, ipos []int16, step int16) {
+	const L = cL_CODE
+	var en [cL_CODE]int16
+
+	s := int32(256)
+	t := int32(256)
+	for i := 0; i < L; i++ {
+		s = L_mac(s, cn[i], cn[i])
+		t += (int32(dn[i]) * int32(dn[i])) << 1
+	}
+	s = invSqrt(s)
+	kCn := int16(L_shl(s, 5) >> 16)
+	t = invSqrt(t)
+	kDn := int16(t >> 11)
+
+	for i := L - 1; i >= 0; i-- {
+		lTemp := (int32(kCn) * int32(cn[i])) << 1
+		val := dn[i]
+		ss := L_mac(lTemp, kDn, val)
+		cor := round_(L_shl(ss, 10))
+		if cor >= 0 {
+			sign[i] = 32767
+		} else {
+			sign[i] = -32767
+			cor = negate(cor)
+			dn[i] = negate(val)
+		}
+		en[i] = cor
+	}
+
+	maxOfAll := int16(-1)
+	var pos int16
+	for i := int16(0); i < nbTrack; i++ {
+		max := int16(-1)
+		for j := i; j < L; j += step {
+			if en[j] > max {
+				max = en[j]
+				pos = j
+			}
+		}
+		posMax[i] = pos
+		if max > maxOfAll {
+			maxOfAll = max
+			ipos[0] = i
+		}
+	}
+
+	pos = ipos[0]
+	ipos[nbTrack] = pos
+	for i := int16(1); i < nbTrack; i++ {
+		pos++
+		if pos >= nbTrack {
+			pos = 0
+		}
+		ipos[i] = pos
+		ipos[i+nbTrack] = pos
+	}
+}