--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/amrconv/if1_unpack.c	Thu Apr 20 22:48:22 2023 +0000
@@ -0,0 +1,79 @@
+/*
+ * In this module we implement our function for unpacking bits from AMR IF1
+ * and reshuffling them into the codec's natural bit order.
+ */
+
+#include <stdint.h>
+#include "amr_defs.h"
+
+extern const uint8_t amr_475_bit_order[95];
+extern const uint8_t amr_515_bit_order[103];
+extern const uint8_t amr_59_bit_order[118];
+extern const uint8_t amr_67_bit_order[134];
+extern const uint8_t amr_74_bit_order[148];
+extern const uint8_t amr_795_bit_order[159];
+extern const uint8_t amr_102_bit_order[204];
+extern const uint8_t amr_122_bit_order[244];
+
+static void
+unpack_bits(if1_bytes, codec_bits, nbits, table)
+	uint8_t *if1_bytes, *codec_bits;
+	unsigned nbits;
+	const uint8_t *table;
+{
+	unsigned n, nb;
+
+	for (n = 0; n < nbits; n++) {
+		if (table)
+			nb = table[n];
+		else
+			nb = n;
+		codec_bits[nb] = msb_get_bit(if1_bytes, n);
+	}
+}
+
+amr_if1_unpack(if1_bytes, codec_bits, mode)
+	uint8_t *if1_bytes, *codec_bits;
+	unsigned mode;
+{
+	switch (mode) {
+	case MR475:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_475,
+				amr_475_bit_order);
+		return(0);
+	case MR515:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_515,
+				amr_515_bit_order);
+		return(0);
+	case MR59:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_59,
+				amr_59_bit_order);
+		return(0);
+	case MR67:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_67,
+				amr_67_bit_order);
+		return(0);
+	case MR74:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_74,
+				amr_74_bit_order);
+		return(0);
+	case MR795:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_795,
+				amr_795_bit_order);
+		return(0);
+	case MR102:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_102,
+				amr_102_bit_order);
+		return(0);
+	case MR122:            
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_122,
+				amr_122_bit_order);
+		return(0);
+	case MRDTX:
+		unpack_bits(if1_bytes, codec_bits, AMR_NBITS_SID,
+				(const uint8_t *) 0);
+		return(0);
+	default:
+		return(-1);
+	}
+}