More OKed AAC decoder code hunks

Originally committed as revision 14829 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/aac.c

@@ -604,6 +604,44 @@ static void decode_pulses(Pulse * pulse, GetBitContext * gb, const uint16_t * sw
     }
 }
 
+/**
+ * Decode Temporal Noise Shaping data; reference: table 4.48.
+ *
+ * @return  Returns error status. 0 - OK, !0 - error
+ */
+static int decode_tns(AACContext * ac, TemporalNoiseShaping * tns,
+        GetBitContext * gb, const IndividualChannelStream * ics) {
+    int w, filt, i, coef_len, coef_res, coef_compress;
+    const int is8 = ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE;
+    const int tns_max_order = is8 ? 7 : ac->m4ac.object_type == AOT_AAC_MAIN ? 20 : 12;
+    for (w = 0; w < ics->num_windows; w++) {
+        tns->n_filt[w] = get_bits(gb, 2 - is8);
+
+        if (tns->n_filt[w])
+            coef_res = get_bits1(gb);
+
+        for (filt = 0; filt < tns->n_filt[w]; filt++) {
+            int tmp2_idx;
+            tns->length[w][filt] = get_bits(gb, 6 - 2*is8);
+
+            if ((tns->order[w][filt] = get_bits(gb, 5 - 2*is8)) > tns_max_order) {
+                av_log(ac->avccontext, AV_LOG_ERROR, "TNS filter order %d is greater than maximum %d.",
+                       tns->order[w][filt], tns_max_order);
+                tns->order[w][filt] = 0;
+                return -1;
+            }
+            tns->direction[w][filt] = get_bits1(gb);
+            coef_compress = get_bits1(gb);
+            coef_len = coef_res + 3 - coef_compress;
+            tmp2_idx = 2*coef_compress + coef_res;
+
+            for (i = 0; i < tns->order[w][filt]; i++)
+                tns->coef[w][filt][i] = tns_tmp2_map[tmp2_idx][get_bits(gb, coef_len)];
+        }
+    }
+    return 0;
+}
+
 /**
  * Decode Mid/Side data; reference: table 4.54.
  *
@@ -1066,6 +1104,25 @@ static int decode_extension_payload(AACContext * ac, GetBitContext * gb, int cnt
     return res;
 }
 
+            start = ics->swb_offset[FFMIN(bottom, mmm)];
+            end   = ics->swb_offset[FFMIN(   top, mmm)];
+            if ((size = end - start) <= 0)
+                continue;
+            if (tns->direction[w][filt]) {
+                inc = -1; start = end - 1;
+            } else {
+                inc = 1;
+            }
+            start += w * 128;
+
+            // ar filter
+            for (m = 0; m < size; m++, start += inc)
+                for (i = 1; i <= FFMIN(m, order); i++)
+                    coef[start] -= coef[start - i*inc] * lpc[i];
+        }
+    }
+}
+
 /**
  * Conduct IMDCT and windowing.
  */

libavcodec/aac.h

@@ -148,6 +148,18 @@ typedef struct {
     int tns_max_bands;
 } IndividualChannelStream;
 
+/**
+ * Temporal Noise Shaping
+ */
+typedef struct {
+    int present;
+    int n_filt[8];
+    int length[8][4];
+    int direction[8][4];
+    int order[8][4];
+    float coef[8][4][TNS_MAX_ORDER];
+} TemporalNoiseShaping;
+
 /**
  * Dynamic Range Control - decoded from the bitstream but not processed further.
  */

libavcodec/aacdectab.h

@@ -171,4 +171,39 @@ static const uint8_t tns_max_bands_128[] = {
 };
 // @}
 
+/* @name tns_tmp2_map
+ * Tables of the tmp2[] arrays of LPC coefficients used for TNS.
+ * The suffix _M_N[] indicate the values of coef_compress and coef_res
+ * respectively.
+ * @{
+ */
+static const float tns_tmp2_map_1_3[4] = {
+     0.00000000,  0.43388373, -0.64278758, -0.34202015,
+};
+
+static const float tns_tmp2_map_0_3[8] = {
+     0.00000000,  0.43388373,  0.78183150,  0.97492790,
+    -0.98480773, -0.86602539, -0.64278758, -0.34202015,
+};
+
+static const float tns_tmp2_map_1_4[8] = {
+     0.00000000,  0.20791170,  0.40673664,  0.58778524,
+    -0.67369562, -0.52643216, -0.36124167, -0.18374951,
+};
+
+static const float tns_tmp2_map_0_4[16] = {
+     0.00000000,  0.20791170,  0.40673664,  0.58778524,
+     0.74314481,  0.86602539,  0.95105654,  0.99452192,
+    -0.99573416, -0.96182561, -0.89516330, -0.79801720,
+    -0.67369562, -0.52643216, -0.36124167, -0.18374951,
+};
+
+static const float *tns_tmp2_map[4] = {
+    tns_tmp2_map_0_3,
+    tns_tmp2_map_0_4,
+    tns_tmp2_map_1_3,
+    tns_tmp2_map_1_4
+};
+// @}
+
 #endif /* FFMPEG_AACDECTAB_H */