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_az_lsp.go

@@ -0,0 +1,127 @@
+package amrnb
+
+// A(z) -> LSP conversion, ported from opencore-amrnb az_lsp.cpp (Chebps, Az_lsp).
+// Az_lsp finds the line spectral pairs of an order-10 LP filter by locating the
+// roots of the symmetric/antisymmetric polynomials F1(z)/F2(z) on the unit
+// circle, evaluated via the Chebyshev recursion (Chebps) over the cosine grid.
+// This is the encoder-side inverse of lspAz. Bit-exact with the reference.
+
+const cNC = cM / 2 // 5
+
+// chebps evaluates the Chebyshev series of f at x. Mirrors Chebps.
+func chebps(x int16, f []int16, n int) int16 {
+	pf := 1
+	lTemp := int32(0x01000000)
+	t0 := (int32(x) << 10) + (int32(f[pf]) << 14)
+	pf++
+	b1h := int16(t0 >> 16)
+	b1l := int16((t0 >> 1) - (int32(b1h) << 15))
+
+	for i := 2; i < n; i++ {
+		t0 = int32(b1h) * int32(x)
+		t0 += (int32(b1l) * int32(x)) >> 15
+		t0 <<= 2
+		t0 -= lTemp
+		t0 += int32(f[pf]) << 14
+		pf++
+		lTemp = (int32(b1h) << 16) + (int32(b1l) << 1)
+		b1h = int16(t0 >> 16)
+		b1l = int16((t0 >> 1) - (int32(b1h) << 15))
+	}
+
+	t0 = int32(b1h) * int32(x)
+	t0 += (int32(b1l) * int32(x)) >> 15
+	t0 <<= 1
+	t0 -= lTemp
+	t0 += int32(f[pf]) << 13
+
+	if uint32(t0+33554432) < 67108863 {
+		return int16(t0 >> 10)
+	} else if t0 > 0x01ffffff {
+		return maxInt16
+	}
+	return minInt16
+}
+
+// azLsp converts order-10 LP coefficients a[0:M+1] to line spectral pairs
+// lsp[0:M]. oldLsp is reused if fewer than M roots are found. Mirrors Az_lsp.
+func azLsp(a, lsp, oldLsp []int16) {
+	var f1, f2 [cNC + 1]int16
+	f1[0] = 1024
+	f2[0] = 1024
+	for i := 0; i < cNC; i++ {
+		lt1 := int32(a[i+1])
+		lt2 := int32(a[cM-i])
+		x := int16((lt1 + lt2) >> 2)
+		y := int16((lt1 - lt2) >> 2)
+		x -= f1[i]
+		f1[i+1] = x
+		y += f2[i]
+		f2[i+1] = y
+	}
+
+	nf := 0
+	ip := 0
+	coef := f1[:]
+
+	xlow := grid[0]
+	ylow := chebps(xlow, coef, cNC)
+
+	j := 0
+	for nf < cM && j < 60 {
+		j++
+		xhigh := xlow
+		yhigh := ylow
+		xlow = grid[j]
+		ylow = chebps(xlow, coef, cNC)
+
+		if int32(ylow)*int32(yhigh) <= 0 {
+			for i := 4; i != 0; i-- {
+				xmid := (xlow >> 1) + (xhigh >> 1)
+				ymid := chebps(xmid, coef, cNC)
+				if int32(ylow)*int32(ymid) <= 0 {
+					yhigh = ymid
+					xhigh = xmid
+				} else {
+					ylow = ymid
+					xlow = xmid
+				}
+			}
+
+			x := xhigh - xlow
+			yv := yhigh - ylow
+			var xint int16
+			if yv == 0 {
+				xint = xlow
+			} else {
+				sign := yv
+				yv = abs_s(yv)
+				exp := norm_s(yv)
+				yv = shl(yv, exp)
+				yv = div_s(16383, yv)
+				yv = int16((int32(x) * int32(yv)) >> uint(19-exp))
+				if sign < 0 {
+					yv = -yv
+				}
+				xint = int16(int32(xlow) - ((int32(ylow) * int32(yv)) >> 10))
+			}
+
+			lsp[nf] = xint
+			xlow = xint
+			nf++
+
+			if ip == 0 {
+				ip = 1
+				coef = f2[:]
+			} else {
+				ip = 0
+				coef = f1[:]
+			}
+			ylow = chebps(xlow, coef, cNC)
+		}
+	}
+
+	if nf < cM {
+		copy(lsp[:cM], oldLsp[:cM])
+	}
+}