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Diffstat (limited to 'third_party/libwebrtc/modules/audio_coding/codecs/ilbc/gain_quant.c')
-rw-r--r-- | third_party/libwebrtc/modules/audio_coding/codecs/ilbc/gain_quant.c | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/gain_quant.c b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/gain_quant.c new file mode 100644 index 0000000000..9a6d49d51a --- /dev/null +++ b/third_party/libwebrtc/modules/audio_coding/codecs/ilbc/gain_quant.c @@ -0,0 +1,105 @@ +/* + * 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 "modules/audio_coding/codecs/ilbc/gain_quant.h" + +#include "modules/audio_coding/codecs/ilbc/constants.h" +#include "modules/audio_coding/codecs/ilbc/defines.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, 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 = 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 = 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 = scale * *cbPtr; + if (gainW32>measure1) { + /* Check against value above loc */ + measure2 = scale * cbPtr[1]; + if ((measure2-gainW32)<(gainW32-measure1)) { + loc+=1; + } + } else { + /* Check against value below loc */ + measure2 = 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 and return the quantized gain value (in Q14) */ + return (int16_t)((scale * cb[loc] + 8192) >> 14); +} |