X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=src%2Fcore%2Fao_viterbi.c;h=7768155669847c62ebb77ad87968f904bc3dd917;hp=17464cd1df3fd94cbf3a80638e2d17890a9cd901;hb=628076aa90e7bc9a894646e417dd8e1fe149b60d;hpb=566a0c277de01963922cabc80db8ec3a129923bd

diff --git a/src/core/ao_viterbi.c b/src/core/ao_viterbi.c
index 17464cd1..77681556 100644
--- a/src/core/ao_viterbi.c
+++ b/src/core/ao_viterbi.c
@@ -18,6 +18,35 @@
 #include <ao_fec.h>
 #include <stdio.h>
 
+/* 
+ * byte order repeats through 3 2 1 0
+ * 	
+ * bit-pair order repeats through
+ *
+ *  1/0 3/2 5/4 7/6
+ *
+ * So, the over all order is:
+ *
+ *	3,1/0 	2,1/0	1,1/0	0,1/0
+ *	3,3/2 	2,3/2	1,3/2	0,3/2
+ *	3,5/4	2,5/4	1,5/4	0,5/4
+ *	3,7/6	2,7/6	1,7/6	0,7/6
+ *
+ * The raw bit order is thus
+ *
+ *	1e/1f   16/17   0e/0f   06/07
+ *	1c/1d	14/15	0c/0d	04/05
+ *	1a/1b	12/13	0a/0b	02/03
+ *	18/19	10/11	08/09	00/01
+ */
+
+static inline uint16_t ao_interleave_index(uint16_t i) {
+	uint8_t		l = i & 0x1e;
+	uint16_t	h = i & ~0x1e;
+	uint8_t		o = 0x1e ^ (((l >> 2) & 0x6) | ((l << 2) & 0x18));
+	return h | o;
+}
+
 struct ao_soft_sym {
 	uint8_t	a, b;
 };
@@ -26,16 +55,19 @@ struct ao_soft_sym {
 #define NUM_HIST	8
 #define MOD_HIST(b)	((b) & 7)
 
+#define V_0		0xc0
+#define V_1		0x40
+
 static const struct ao_soft_sym ao_fec_decode_table[NUM_STATE][2] = {
 /* next        0              1	         state */
-	{ { 0x00, 0x00 }, { 0xff, 0xff } } ,	/* 000 */
-	{ { 0x00, 0xff }, { 0xff, 0x00 } },	/* 001 */
-	{ { 0xff, 0xff }, { 0x00, 0x00 } },	/* 010 */
-	{ { 0xff, 0x00 }, { 0x00, 0xff } },	/* 011 */
-	{ { 0xff, 0xff }, { 0x00, 0x00 } },	/* 100 */
-	{ { 0xff, 0x00 }, { 0x00, 0xff } },	/* 101 */
-	{ { 0x00, 0x00 }, { 0xff, 0xff } },	/* 110 */
-	{ { 0x00, 0xff }, { 0xff, 0x00 } }	/* 111 */
+	{ { V_0, V_0 }, { V_1, V_1 } } ,	/* 000 */
+	{ { V_0, V_1 }, { V_1, V_0 } },	/* 001 */
+	{ { V_1, V_1 }, { V_0, V_0 } },	/* 010 */
+	{ { V_1, V_0 }, { V_0, V_1 } },	/* 011 */
+	{ { V_1, V_1 }, { V_0, V_0 } },	/* 100 */
+	{ { V_1, V_0 }, { V_0, V_1 } },	/* 101 */
+	{ { V_0, V_0 }, { V_1, V_1 } },	/* 110 */
+	{ { V_0, V_1 }, { V_1, V_0 } }	/* 111 */
 };
 
 static inline uint8_t
@@ -59,7 +91,7 @@ ao_cost(struct ao_soft_sym a, struct ao_soft_sym b)
  */
 
 uint8_t
-ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
+ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len)
 {
 	static uint16_t	cost[2][NUM_STATE];		/* path cost */
 	static uint16_t	bits[2][NUM_STATE];		/* save bits to quickly output them */
@@ -70,6 +102,9 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
 	uint8_t		n;				/* next cost/bits index */
 	uint8_t		state;				/* state index */
 	uint8_t		bit;				/* original encoded bit index */
+	const uint8_t	*whiten = ao_fec_whiten_table;
+	uint16_t	interleave;			/* input byte array index */
+	struct ao_soft_sym	s;			/* input symbol pair */
 
 	p = 0;
 	for (state = 0; state < NUM_STATE; state++) {
@@ -82,7 +117,13 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
 	for (i = 0; i < len; i += 2) {
 		b = i/2;
 		n = p ^ 1;
-		struct ao_soft_sym s = { .a = in[i], .b = in[i+1] };
+
+		/* Fetch one pair of input bytes, de-interleaving
+		 * the input.
+		 */
+		interleave = ao_interleave_index(i);
+		s.a = in[interleave];
+		s.b = in[interleave+1];
 
 		/* Reset next costs to 'impossibly high' values so that
 		 * the first path through this state is cheaper than this
@@ -159,10 +200,13 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
 			}
 
 #if 0
-			printf ("\tbit %3d min_cost %5d old bit %3d old_state %x bits %02x\n",
-				i/2, min_cost, o + 8, min_state, (bits[p][min_state] >> dist) & 0xff);
+			printf ("\tbit %3d min_cost %5d old bit %3d old_state %x bits %02x whiten %0x\n",
+				i/2, min_cost, o + 8, min_state, (bits[p][min_state] >> dist) & 0xff, *whiten);
 #endif
-			out[o >> 3] = bits[p][min_state] >> dist;
+			if (out_len) {
+				*out++ = (bits[p][min_state] >> dist) ^ *whiten++;
+				--out_len;
+			}
 			o += 8;
 		}
 	}