git-svn-id: http://webrtc.googlecode.com/svn/trunk@4 4adac7df-926f-26a2-2b94-8c16560cd09d

2011-05-30 11:22:19 +00:00
parent 01813fe945
commit 77ae29bc81
1153 changed files with 404089 additions and 0 deletions
--- a/modules/audio_coding/codecs/iLBC/main/source/gain_quant.c
+++ b/modules/audio_coding/codecs/iLBC/main/source/gain_quant.c
@@ -0,0 +1,106 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+/******************************************************************
+
+ iLBC Speech Coder ANSI-C Source Code
+
+ WebRtcIlbcfix_GainQuant.c
+
+******************************************************************/
+
+#include "defines.h"
+#include "constants.h"
+
+/*----------------------------------------------------------------*
+ *  quantizer for the gain in the gain-shape coding of residual
+ *---------------------------------------------------------------*/
+
+WebRtc_Word16 WebRtcIlbcfix_GainQuant( /* (o) quantized gain value */
+    WebRtc_Word16 gain, /* (i) gain value Q14 */
+    WebRtc_Word16 maxIn, /* (i) maximum of gain value Q14 */
+    WebRtc_Word16 stage, /* (i) The stage of the search */
+    WebRtc_Word16 *index /* (o) quantization index */
+                                        ) {
+
+  WebRtc_Word16 scale, returnVal, cblen;
+  WebRtc_Word32 gainW32, measure1, measure2;
+  const WebRtc_Word16 *cbPtr, *cb;
+  int loc, noMoves, noChecks, i;
+
+  /* ensure a lower bound (0.1) on the scaling factor */
+
+  scale = WEBRTC_SPL_MAX(1638, maxIn);
+
+  /* select the quantization table and calculate
+     the length of the table and the number of
+     steps in the binary search that are needed */
+  cb = WebRtcIlbcfix_kGain[stage];
+  cblen = 32>>stage;
+  noChecks = 4-stage;
+
+  /* Multiply the gain with 2^14 to make the comparison
+     easier and with higher precision */
+  gainW32 = WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)gain, 14);
+
+  /* Do a binary search, starting in the middle of the CB
+     loc - defines the current position in the table
+     noMoves - defines the number of steps to move in the CB in order
+     to get next CB location
+  */
+
+  loc = cblen>>1;
+  noMoves = loc;
+  cbPtr = cb + loc; /* Centre of CB */
+
+  for (i=noChecks;i>0;i--) {
+    noMoves>>=1;
+    measure1=WEBRTC_SPL_MUL_16_16(scale, (*cbPtr));
+
+    /* Move up if gain is larger, otherwise move down in table */
+    measure1 = measure1 - gainW32;
+
+    if (0>measure1) {
+      cbPtr+=noMoves;
+      loc+=noMoves;
+    } else {
+      cbPtr-=noMoves;
+      loc-=noMoves;
+    }
+  }
+
+  /* Check which value is the closest one: loc-1, loc or loc+1 */
+
+  measure1=WEBRTC_SPL_MUL_16_16(scale, (*cbPtr));
+  if (gainW32>measure1) {
+    /* Check against value above loc */
+    measure2=WEBRTC_SPL_MUL_16_16(scale, (*(cbPtr+1)));
+    if ((measure2-gainW32)<(gainW32-measure1)) {
+      loc+=1;
+    }
+  } else {
+    /* Check against value below loc */
+    measure2=WEBRTC_SPL_MUL_16_16(scale, (*(cbPtr-1)));
+    if ((gainW32-measure2)<=(measure1-gainW32)) {
+      loc-=1;
+    }
+  }
+
+  /* Guard against getting outside the table. The calculation above can give a location
+     which is one above the maximum value (in very rare cases) */
+  loc=WEBRTC_SPL_MIN(loc, (cblen-1));
+  *index=loc;
+
+  /* Calculate the quantized gain value (in Q14) */
+  returnVal=(WebRtc_Word16)((WEBRTC_SPL_MUL_16_16(scale, cb[loc])+8192)>>14);
+
+  /* return the quantized value */
+  return(returnVal);
+}