mirror of
https://github.com/mollyim/webrtc.git
synced 2025-05-14 06:10:40 +01:00
06c2aa9f7b
WebRTC internal code should always use include paths that start from the root of the project and that clearly identify the header file. This allows 'gn check' to actually keep dependencies under control because 'gn check' cannot enforce anything if the include path is not fully qualified (starting from the root of the project). Bug: webrtc:8815 Change-Id: I36f01784fa5f5b77eefc02db479b1f7f6ee1a8c3 Reviewed-on: https://webrtc-review.googlesource.com/46263 Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21871}
84 lines
2.4 KiB
C
84 lines
2.4 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_Lsp2Lsf.c
|
|
|
|
******************************************************************/
|
|
|
|
#include "modules/audio_coding/codecs/ilbc/defines.h"
|
|
#include "modules/audio_coding/codecs/ilbc/constants.h"
|
|
|
|
/*----------------------------------------------------------------*
|
|
* conversion from LSP coefficients to LSF coefficients
|
|
*---------------------------------------------------------------*/
|
|
|
|
void WebRtcIlbcfix_Lsp2Lsf(
|
|
int16_t *lsp, /* (i) lsp vector -1...+1 in Q15 */
|
|
int16_t *lsf, /* (o) Lsf vector 0...Pi in Q13
|
|
(ordered, so that lsf[i]<lsf[i+1]) */
|
|
int16_t m /* (i) Number of coefficients */
|
|
)
|
|
{
|
|
int16_t i, k;
|
|
int16_t diff; /* diff between table value and desired value (Q15) */
|
|
int16_t freq; /* lsf/(2*pi) (Q16) */
|
|
int16_t *lspPtr, *lsfPtr, *cosTblPtr;
|
|
int16_t tmp;
|
|
|
|
/* set the index to maximum index value in WebRtcIlbcfix_kCos */
|
|
k = 63;
|
|
|
|
/*
|
|
Start with the highest LSP and then work the way down
|
|
For each LSP the lsf is calculated by first order approximation
|
|
of the acos(x) function
|
|
*/
|
|
lspPtr = &lsp[9];
|
|
lsfPtr = &lsf[9];
|
|
cosTblPtr=(int16_t*)&WebRtcIlbcfix_kCos[k];
|
|
for(i=m-1; i>=0; i--)
|
|
{
|
|
/*
|
|
locate value in the table, which is just above lsp[i],
|
|
basically an approximation to acos(x)
|
|
*/
|
|
while( (((int32_t)(*cosTblPtr)-(*lspPtr)) < 0)&&(k>0) )
|
|
{
|
|
k-=1;
|
|
cosTblPtr--;
|
|
}
|
|
|
|
/* Calculate diff, which is used in the linear approximation of acos(x) */
|
|
diff = (*lspPtr)-(*cosTblPtr);
|
|
|
|
/*
|
|
The linear approximation of acos(lsp[i]) :
|
|
acos(lsp[i])= k*512 + (WebRtcIlbcfix_kAcosDerivative[ind]*offset >> 11)
|
|
*/
|
|
|
|
/* tmp (linear offset) in Q16 */
|
|
tmp = (int16_t)((WebRtcIlbcfix_kAcosDerivative[k] * diff) >> 11);
|
|
|
|
/* freq in Q16 */
|
|
freq = (k << 9) + tmp;
|
|
|
|
/* lsf = freq*2*pi */
|
|
(*lsfPtr) = (int16_t)(((int32_t)freq*25736)>>15);
|
|
|
|
lsfPtr--;
|
|
lspPtr--;
|
|
}
|
|
|
|
return;
|
|
}
|