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_qgain.go

@@ -0,0 +1,138 @@
+package amrnb
+
+// Gain quantization (general modes), ported from opencore-amrnb qua_gain.cpp
+// (Qua_gain) and calc_en.cpp (calc_filt_energies). calcFiltEnergies forms the
+// five quadratic-form energy coefficients of the gain error from the target,
+// the adaptive codebook y1 and the filtered innovation y2; quaGain searches the
+// gain VQ table for the (pitch, code) gain pair minimizing that error, returning
+// the index and the dequantized gains — the exact encoder counterpart of
+// decGain. Bit-exact with the reference.
+
+const (
+	cVQ_SIZE_HIGHRATES = 128
+	cVQ_SIZE_LOWRATES  = 64
+)
+
+// calcFiltEnergies computes the five energy coefficients (frac/exp) of the gain
+// MSE. gCoeff[0..3] are the <xn,y1>/<y1,y1> correlations from gPitch. For
+// MR795/MR475 it also returns the optimum unconstrained code gain. Mirrors
+// calc_filt_energies.
+func calcFiltEnergies(mode int, xn, xn2, y1, y2, gCoeff []int16) (fracCoeff, expCoeff [5]int16, codGainFrac, codGainExp int16) {
+	fracCoeff[0] = gCoeff[0]
+	expCoeff[0] = gCoeff[1]
+	fracCoeff[1] = negate(gCoeff[2])
+	expCoeff[1] = gCoeff[3] + 1
+
+	var s1, s2, s3 int32
+	if mode != dMR795 && mode != dMR475 {
+		s1, s2, s3 = 1, 1, 1
+	}
+	var scaledY2 [cL_SUBFR]int16
+	for i := 0; i < cL_SUBFR; i++ {
+		tmp := y2[i] >> 3
+		scaledY2[i] = tmp
+		s1 = L_mac(s1, tmp, tmp)
+		s2 = L_mac(s2, xn[i], tmp)
+		s3 = L_mac(s3, y1[i], tmp)
+	}
+	exp := norm_l(s1)
+	fracCoeff[2] = int16(L_shl(s1, exp) >> 16)
+	expCoeff[2] = -3 - exp
+	exp = norm_l(s2)
+	fracCoeff[3] = negate(int16(L_shl(s2, exp) >> 16))
+	expCoeff[3] = 7 - exp
+	exp = norm_l(s3)
+	fracCoeff[4] = int16(L_shl(s3, exp) >> 16)
+	expCoeff[4] = 7 - exp
+
+	if mode == dMR795 || mode == dMR475 {
+		s1 = 0
+		for i := 0; i < cL_SUBFR; i++ {
+			s1 += int32(xn2[i]) * int32(scaledY2[i])
+		}
+		s1 <<= 1
+		exp = norm_l(s1)
+		frac := int16(L_shl(s1, exp) >> 16)
+		exp = 6 - exp
+		if frac <= 0 {
+			codGainFrac = 0
+			codGainExp = 0
+		} else {
+			codGainFrac = div_s(shr(frac, 1), fracCoeff[2])
+			codGainExp = (exp - expCoeff[2]) - 14
+		}
+	}
+	return
+}
+
+// quaGain searches the mode's gain VQ table for the (pitch, code) gain pair
+// minimizing the weighted gain MSE, returning the index and dequantized gains
+// plus the predictor-update energies. Mirrors Qua_gain.
+func quaGain(mode int, expGcode0, fracGcode0 int16, fracCoeff, expCoeff []int16, gpLimit int16) (index, gainPit, gainCod, quaEnerMR122, quaEner int16) {
+	var tableGain []int16
+	var tableLen int
+	if mode == dMR102 || mode == dMR74 || mode == dMR67 {
+		tableLen = cVQ_SIZE_HIGHRATES
+		tableGain = table_gain_highrates
+	} else {
+		tableLen = cVQ_SIZE_LOWRATES
+		tableGain = table_gain_lowrates
+	}
+
+	gcode0 := int16(pow2(14, fracGcode0))
+	expCode := expGcode0 - 11
+
+	var expMax [5]int16
+	expMax[0] = expCoeff[0] - 13
+	expMax[1] = expCoeff[1] - 14
+	temp := shl(expCode, 1) + 15
+	expMax[2] = add(expCoeff[2], temp)
+	expMax[3] = add(expCoeff[3], expCode)
+	expMax[4] = add(expCoeff[4], expCode+1)
+
+	eMax := expMax[0]
+	for i := 1; i < 5; i++ {
+		if expMax[i] > eMax {
+			eMax = expMax[i]
+		}
+	}
+	eMax++
+
+	var coeff, coeffLo [5]int16
+	for i := 0; i < 5; i++ {
+		j := eMax - expMax[i]
+		coeff[i], coeffLo[i] = L_Extract(L_shr(int32(fracCoeff[i])<<16, j))
+	}
+
+	distMin := int32(maxInt32)
+	for i := 0; i < tableLen; i++ {
+		p := i << 2
+		gPitch := tableGain[p]
+		gCode := tableGain[p+1]
+		if gPitch <= gpLimit {
+			gc := mult(gCode, gcode0)
+			g2Pitch := mult(gPitch, gPitch)
+			g2Code := mult(gc, gc)
+			gPitCod := mult(gc, gPitch)
+			L_tmp := mpy32_16(coeff[0], coeffLo[0], g2Pitch)
+			L_tmp = L_add(L_tmp, mpy32_16(coeff[1], coeffLo[1], gPitch))
+			L_tmp = L_add(L_tmp, mpy32_16(coeff[2], coeffLo[2], g2Code))
+			L_tmp = L_add(L_tmp, mpy32_16(coeff[3], coeffLo[3], gc))
+			L_tmp = L_add(L_tmp, mpy32_16(coeff[4], coeffLo[4], gPitCod))
+			if L_tmp < distMin {
+				distMin = L_tmp
+				index = int16(i)
+			}
+		}
+	}
+
+	p := int(index) << 2
+	gainPit = tableGain[p]
+	gCode := tableGain[p+1]
+	quaEnerMR122 = tableGain[p+2]
+	quaEner = tableGain[p+3]
+
+	L_tmp := L_shr(L_mult(gCode, gcode0), 10-expGcode0)
+	gainCod = int16(L_tmp >> 16)
+	return
+}