| /* |
| * 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_HpInput.c |
| |
| ******************************************************************/ |
| |
| #include "defines.h" |
| |
| /*----------------------------------------------------------------* |
| * high-pass filter of input with *0.5 and saturation |
| *---------------------------------------------------------------*/ |
| |
| void WebRtcIlbcfix_HpInput( |
| WebRtc_Word16 *signal, /* (i/o) signal vector */ |
| WebRtc_Word16 *ba, /* (i) B- and A-coefficients (2:nd order) |
| {b[0] b[1] b[2] -a[1] -a[2]} a[0] |
| is assumed to be 1.0 */ |
| WebRtc_Word16 *y, /* (i/o) Filter state yhi[n-1] ylow[n-1] |
| yhi[n-2] ylow[n-2] */ |
| WebRtc_Word16 *x, /* (i/o) Filter state x[n-1] x[n-2] */ |
| WebRtc_Word16 len) /* (i) Number of samples to filter */ |
| { |
| int i; |
| WebRtc_Word32 tmpW32; |
| WebRtc_Word32 tmpW32b; |
| |
| for (i=0; i<len; i++) { |
| |
| /* |
| y[i] = b[0]*x[i] + b[1]*x[i-1] + b[2]*x[i-2] |
| + (-a[1])*y[i-1] + (-a[2])*y[i-2]; |
| */ |
| |
| tmpW32 = WEBRTC_SPL_MUL_16_16(y[1], ba[3]); /* (-a[1])*y[i-1] (low part) */ |
| tmpW32 += WEBRTC_SPL_MUL_16_16(y[3], ba[4]); /* (-a[2])*y[i-2] (low part) */ |
| tmpW32 = (tmpW32>>15); |
| tmpW32 += WEBRTC_SPL_MUL_16_16(y[0], ba[3]); /* (-a[1])*y[i-1] (high part) */ |
| tmpW32 += WEBRTC_SPL_MUL_16_16(y[2], ba[4]); /* (-a[2])*y[i-2] (high part) */ |
| tmpW32 = (tmpW32<<1); |
| |
| tmpW32 += WEBRTC_SPL_MUL_16_16(signal[i], ba[0]); /* b[0]*x[0] */ |
| tmpW32 += WEBRTC_SPL_MUL_16_16(x[0], ba[1]); /* b[1]*x[i-1] */ |
| tmpW32 += WEBRTC_SPL_MUL_16_16(x[1], ba[2]); /* b[2]*x[i-2] */ |
| |
| /* Update state (input part) */ |
| x[1] = x[0]; |
| x[0] = signal[i]; |
| |
| /* Rounding in Q(12+1), i.e. add 2^12 */ |
| tmpW32b = tmpW32 + 4096; |
| |
| /* Saturate (to 2^28) so that the HP filtered signal does not overflow */ |
| tmpW32b = WEBRTC_SPL_SAT((WebRtc_Word32)268435455, tmpW32b, (WebRtc_Word32)-268435456); |
| |
| /* Convert back to Q0 and multiply with 0.5 */ |
| signal[i] = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(tmpW32b, 13); |
| |
| /* Update state (filtered part) */ |
| y[2] = y[0]; |
| y[3] = y[1]; |
| |
| /* upshift tmpW32 by 3 with saturation */ |
| if (tmpW32>268435455) { |
| tmpW32 = WEBRTC_SPL_WORD32_MAX; |
| } else if (tmpW32<-268435456) { |
| tmpW32 = WEBRTC_SPL_WORD32_MIN; |
| } else { |
| tmpW32 = WEBRTC_SPL_LSHIFT_W32(tmpW32, 3); |
| } |
| |
| y[0] = (WebRtc_Word16)(tmpW32 >> 16); |
| y[1] = (WebRtc_Word16)((tmpW32 - WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)y[0], 16))>>1); |
| } |
| |
| return; |
| } |