mirror of
https://github.com/oxen-io/session-android.git
synced 2024-12-21 07:27:30 +00:00
107 lines
3.2 KiB
C
107 lines
3.2 KiB
C
/*
|
|
* 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
|
|
*---------------------------------------------------------------*/
|
|
|
|
int16_t WebRtcIlbcfix_GainQuant( /* (o) quantized gain value */
|
|
int16_t gain, /* (i) gain value Q14 */
|
|
int16_t maxIn, /* (i) maximum of gain value Q14 */
|
|
int16_t stage, /* (i) The stage of the search */
|
|
int16_t *index /* (o) quantization index */
|
|
) {
|
|
|
|
int16_t scale, returnVal, cblen;
|
|
int32_t gainW32, measure1, measure2;
|
|
const int16_t *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((int32_t)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=(int16_t)((WEBRTC_SPL_MUL_16_16(scale, cb[loc])+8192)>>14);
|
|
|
|
/* return the quantized value */
|
|
return(returnVal);
|
|
}
|