Initial import of NFC GNSS SDK project

2026-09-15 16:10:12 +08:00
commit 2746cc3d4e
3070 changed files with 892062 additions and 0 deletions
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+/* reservoir.c
+ * Layer3 bit reservoir: Described in C.1.5.4.2.2 of the IS
+ */
+
+#include "reservoir.h"
+#include "bitstream.h"
+#include "huffman.h"
+#include "l3bitstream.h"
+#include "l3loop.h"
+#include "layer3.h"
+#include "types.h"
+
+/*
+ * shine_max_reservoir_bits:
+ * ------------
+ * Called at the beginning of each granule to get the max bit
+ * allowance for the current granule based on reservoir size
+ * and perceptual entropy.
+ */
+int shine_max_reservoir_bits(double *pe, shine_global_config *config) {
+  int more_bits, max_bits, add_bits, over_bits;
+  int mean_bits = config->mean_bits;
+
+  mean_bits /= config->wave.channels;
+  max_bits = mean_bits;
+
+  if (max_bits > 4095)
+    max_bits = 4095;
+  if (!config->ResvMax)
+    return max_bits;
+
+  more_bits = *pe * 3.1 - mean_bits;
+  add_bits = 0;
+  if (more_bits > 100) {
+    int frac = (config->ResvSize * 6) / 10;
+
+    if (frac < more_bits)
+      add_bits = frac;
+    else
+      add_bits = more_bits;
+  }
+  over_bits = config->ResvSize - ((config->ResvMax << 3) / 10) - add_bits;
+  if (over_bits > 0)
+    add_bits += over_bits;
+
+  max_bits += add_bits;
+  if (max_bits > 4095)
+    max_bits = 4095;
+  return max_bits;
+}
+
+/*
+ * shine_ResvAdjust:
+ * -----------
+ * Called after a granule's bit allocation. Readjusts the size of
+ * the reservoir to reflect the granule's usage.
+ */
+void shine_ResvAdjust(gr_info *gi, shine_global_config *config) {
+  config->ResvSize +=
+      (config->mean_bits / config->wave.channels) - gi->part2_3_length;
+}
+
+/*
+ * shine_ResvFrameEnd:
+ * -------------
+ * Called after all granules in a frame have been allocated. Makes sure
+ * that the reservoir size is within limits, possibly by adding stuffing
+ * bits. Note that stuffing bits are added by increasing a granule's
+ * part2_3_length. The bitstream formatter will detect this and write the
+ * appropriate stuffing bits to the bitstream.
+ */
+void shine_ResvFrameEnd(shine_global_config *config) {
+  gr_info *gi;
+  int gr, ch, ancillary_pad, stuffingBits;
+  int over_bits;
+  shine_side_info_t *l3_side = &config->side_info;
+
+  ancillary_pad = 0;
+
+  /* just in case mean_bits is odd, this is necessary... */
+  if ((config->wave.channels == 2) && (config->mean_bits & 1))
+    config->ResvSize += 1;
+
+  over_bits = config->ResvSize - config->ResvMax;
+  if (over_bits < 0)
+    over_bits = 0;
+
+  config->ResvSize -= over_bits;
+  stuffingBits = over_bits + ancillary_pad;
+
+  /* we must be byte aligned */
+  if ((over_bits = config->ResvSize % 8)) {
+    stuffingBits += over_bits;
+    config->ResvSize -= over_bits;
+  }
+
+  if (stuffingBits) {
+    /*
+     * plan a: put all into the first granule
+     * This was preferred by someone designing a
+     * real-time decoder...
+     */
+    gi = (gr_info *)&(l3_side->gr[0].ch[0]);
+
+    if (gi->part2_3_length + stuffingBits < 4095)
+      gi->part2_3_length += stuffingBits;
+    else {
+      /* plan b: distribute throughout the granules */
+      for (gr = 0; gr < config->mpeg.granules_per_frame; gr++)
+        for (ch = 0; ch < config->wave.channels; ch++) {
+          int extraBits, bitsThisGr;
+          gr_info *gi = (gr_info *)&(l3_side->gr[gr].ch[ch]);
+          if (!stuffingBits)
+            break;
+          extraBits = 4095 - gi->part2_3_length;
+          bitsThisGr = extraBits < stuffingBits ? extraBits : stuffingBits;
+          gi->part2_3_length += bitsThisGr;
+          stuffingBits -= bitsThisGr;
+        }
+      /*
+       * If any stuffing bits remain, we elect to spill them
+       * into ancillary data. The bitstream formatter will do this if
+       * l3side->resvDrain is set
+       */
+      l3_side->resvDrain = stuffingBits;
+    }
+  }
+}