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_bits.go

@@ -0,0 +1,50 @@
+package amrnb
+
+// Decoder-side bit de-serialization, ported from opencore-amrnb bits2prm.cpp
+// (Bin2int/Bits2prm) and the IETF->ETS reordering in wmf_to_ets.cpp (used for
+// MIME_IETF input). The chain inverts the encoder side: IETF storage bytes ->
+// ETS serial bits (unpacked MSB-first then inverse-permuted by reorderBits) ->
+// parameter array (each parameter read MSB-first from its bitno width).
+
+// bin2int reads nBits from bits[0:nBits], MSB first (bits[0] is the most
+// significant bit), and returns the assembled value. Mirrors Bin2int.
+func bin2int(nBits int, bits []int16) int16 {
+	var v int16
+	for i := 0; i < nBits; i++ {
+		v = (v << 1) | (bits[i] & 1)
+	}
+	return v
+}
+
+// ietfToEts unpacks the RFC 4867 speech payload bytes (IETF storage order,
+// MSB-first) and inverse-permutes them via reorderBits[mode] into the ETS
+// serial bit array. Mirrors the speech branch of wmf_to_ets.
+func ietfToEts(mode Mode, data []byte) []int16 {
+	nb := modeBits[mode]
+	ro := reorderBits[mode]
+	ets := make([]int16, nb)
+	for i := 0; i < nb; i++ {
+		bit := (data[i>>3] >> uint(7-(i&7))) & 1
+		ets[ro[i]] = int16(bit)
+	}
+	return ets
+}
+
+// bits2prm reads the ETS serial bit array back into the mode's parameter array.
+// Mirrors Bits2prm.
+func bits2prm(mode Mode, ets []int16) []int16 {
+	bn := bitno[mode]
+	prm := make([]int16, len(bn))
+	pos := 0
+	for i, w := range bn {
+		prm[i] = bin2int(int(w), ets[pos:])
+		pos += int(w)
+	}
+	return prm
+}
+
+// mimeUnsort decodes the RFC 4867 speech payload bytes for the given mode into
+// the decoder parameter array (the inverse of packFrame).
+func mimeUnsort(data []byte, mode Mode) []int16 {
+	return bits2prm(mode, ietfToEts(mode, data))
+}