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Protect against divide-by-zeros in AGC.

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TEST=audioproc_unittest

Review URL: http://webrtc-codereview.appspot.com/333024

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1331 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
andrew@webrtc.org 2012-01-04 15:47:20 +00:00
parent c450a19669
commit 3905b0c45d
2 changed files with 21 additions and 5 deletions
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4
src/modules/audio_processing/agc/analog_agc.c
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@ -200,6 +200,10 @@ int WebRtcAgc_AddMic(void *state, WebRtc_Word16 *in_mic, WebRtc_Word16 *in_mic_H
/* apply slowly varying digital gain */ /* apply slowly varying digital gain */
if (stt->micVol > stt->maxAnalog) if (stt->micVol > stt->maxAnalog)
{ {
/* |maxLevel| is strictly >= |micVol|, so this condition should be
* satisfied here, ensuring there is no divide-by-zero. */
assert(stt->maxLevel > stt->maxAnalog);
/* Q1 */ /* Q1 */
tmp16 = (WebRtc_Word16)(stt->micVol - stt->maxAnalog); tmp16 = (WebRtc_Word16)(stt->micVol - stt->maxAnalog);
tmp32 = WEBRTC_SPL_MUL_16_16(GAIN_TBL_LEN - 1, tmp16); tmp32 = WEBRTC_SPL_MUL_16_16(GAIN_TBL_LEN - 1, tmp16);

22
src/modules/audio_processing/agc/digital_agc.c
View File

@ -12,11 +12,14 @@
* *
*/ */
#include "digital_agc.h"
#include <assert.h>
#include <string.h> #include <string.h>
#ifdef AGC_DEBUG #ifdef AGC_DEBUG
#include <stdio.h> #include <stdio.h>
#endif #endif
#include "digital_agc.h"
#include "gain_control.h" #include "gain_control.h"
// To generate the gaintable, copy&paste the following lines to a Matlab window: // To generate the gaintable, copy&paste the following lines to a Matlab window:
@ -33,7 +36,8 @@
// zoom on; // zoom on;
// Generator table for y=log2(1+e^x) in Q8. // Generator table for y=log2(1+e^x) in Q8.
static const WebRtc_UWord16 kGenFuncTable[128] = { static const int kGenFuncTableSize = 128;
static const WebRtc_UWord16 kGenFuncTable[kGenFuncTableSize] = {
256, 485, 786, 1126, 1484, 1849, 2217, 2586, 256, 485, 786, 1126, 1484, 1849, 2217, 2586,
2955, 3324, 3693, 4063, 4432, 4801, 5171, 5540, 2955, 3324, 3693, 4063, 4432, 4801, 5171, 5540,
5909, 6279, 6648, 7017, 7387, 7756, 8125, 8495, 5909, 6279, 6648, 7017, 7387, 7756, 8125, 8495,
@ -102,8 +106,9 @@ WebRtc_Word32 WebRtcAgc_CalculateGainTable(WebRtc_Word32 *gainTable, // Q16
// = (compRatio-1)*digCompGaindB/compRatio // = (compRatio-1)*digCompGaindB/compRatio
tmp32no1 = WEBRTC_SPL_MUL_16_16(digCompGaindB, kCompRatio - 1); tmp32no1 = WEBRTC_SPL_MUL_16_16(digCompGaindB, kCompRatio - 1);
diffGain = WebRtcSpl_DivW32W16ResW16(tmp32no1 + (kCompRatio >> 1), kCompRatio); diffGain = WebRtcSpl_DivW32W16ResW16(tmp32no1 + (kCompRatio >> 1), kCompRatio);
if (diffGain < 0) if (diffGain < 0 || diffGain >= kGenFuncTableSize)
{ {
assert(0);
return -1; return -1;
} }
@ -185,8 +190,15 @@ WebRtc_Word32 WebRtcAgc_CalculateGainTable(WebRtc_Word32 *gainTable, // Q16
numFIX -= WEBRTC_SPL_MUL_32_16((WebRtc_Word32)logApprox, diffGain); // Q14 numFIX -= WEBRTC_SPL_MUL_32_16((WebRtc_Word32)logApprox, diffGain); // Q14
// Calculate ratio // Calculate ratio
// Shift numFIX as much as possible // Shift |numFIX| as much as possible.
zeros = WebRtcSpl_NormW32(numFIX); // Ensure we avoid wrap-around in |den| as well.
if (numFIX > (den >> 8)) // |den| is Q8.
{
zeros = WebRtcSpl_NormW32(numFIX);
} else
{
zeros = WebRtcSpl_NormW32(den) + 8;
}
numFIX = WEBRTC_SPL_LSHIFT_W32(numFIX, zeros); // Q(14+zeros) numFIX = WEBRTC_SPL_LSHIFT_W32(numFIX, zeros); // Q(14+zeros)
// Shift den so we end up in Qy1 // Shift den so we end up in Qy1