diff options
Diffstat (limited to 'media/libstagefright/codecs/amrwbenc/src/hp400.c')
| -rw-r--r-- | media/libstagefright/codecs/amrwbenc/src/hp400.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/amrwbenc/src/hp400.c b/media/libstagefright/codecs/amrwbenc/src/hp400.c new file mode 100644 index 0000000..463a53a --- /dev/null +++ b/media/libstagefright/codecs/amrwbenc/src/hp400.c @@ -0,0 +1,106 @@ +/*
+ ** Copyright 2003-2010, VisualOn, Inc.
+ **
+ ** Licensed under the Apache License, Version 2.0 (the "License");
+ ** you may not use this file except in compliance with the License.
+ ** You may obtain a copy of the License at
+ **
+ ** http://www.apache.org/licenses/LICENSE-2.0
+ **
+ ** Unless required by applicable law or agreed to in writing, software
+ ** distributed under the License is distributed on an "AS IS" BASIS,
+ ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ ** See the License for the specific language governing permissions and
+ ** limitations under the License.
+ */
+
+/***********************************************************************
+* File: hp400.c *
+* *
+* Description: *
+* 2nd order high pass filter with cut off frequency at 400 Hz. *
+* Designed with cheby2 function in MATLAB. *
+* Optimized for fixed-point to get the following frequency response: *
+* *
+* frequency: 0Hz 100Hz 200Hz 300Hz 400Hz 630Hz 1.5kHz 3kHz *
+* dB loss: -infdB -30dB -20dB -10dB -3dB +6dB +1dB 0dB *
+* *
+* Algorithm: *
+* *
+* 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]; *
+* *
+* Word16 b[3] = {3660, -7320, 3660}; in Q12 *
+* Word16 a[3] = {4096, 7320, -3540}; in Q12 *
+* *
+* float --> b[3] = {0.893554687, -1.787109375, 0.893554687}; *
+* a[3] = {1.000000000, 1.787109375, -0.864257812}; *
+* *
+************************************************************************/
+
+#include "typedef.h"
+#include "basic_op.h"
+#include "oper_32b.h"
+#include "acelp.h"
+
+/* filter coefficients */
+static Word16 b[3] = {915, -1830, 915}; /* Q12 (/4) */
+static Word16 a[3] = {16384, 29280, -14160}; /* Q12 (x4) */
+/* Initialization of static values */
+
+void Init_HP400_12k8(Word16 mem[])
+{
+ Set_zero(mem, 6);
+}
+
+
+void HP400_12k8(
+ Word16 signal[], /* input signal / output is divided by 16 */
+ Word16 lg, /* lenght of signal */
+ Word16 mem[] /* filter memory [6] */
+ )
+{
+ Word16 x2;
+ Word16 y2_hi, y2_lo, y1_hi, y1_lo, x0, x1;
+ Word32 L_tmp;
+ Word32 num;
+ y2_hi = *mem++;
+ y2_lo = *mem++;
+ y1_hi = *mem++;
+ y1_lo = *mem++;
+ x0 = *mem++;
+ x1 = *mem;
+ num = (Word32)lg;
+ do
+ {
+ x2 = x1;
+ x1 = x0;
+ x0 = *signal;
+ /* y[i] = b[0]*x[i] + b[1]*x[i-1] + b140[2]*x[i-2] */
+ /* + a[1]*y[i-1] + a[2] * y[i-2]; */
+ L_tmp = 8192L; /* rounding to maximise precision */
+ L_tmp += y1_lo * a[1];
+ L_tmp += y2_lo * a[2];
+ L_tmp = L_tmp >> 14;
+ L_tmp += (y1_hi * a[1] + y2_hi * a[2] + (x0 + x2)* b[0] + x1 * b[1]) << 1;
+ L_tmp <<= 1; /* coeff Q12 --> Q13 */
+ y2_hi = y1_hi;
+ y2_lo = y1_lo;
+ y1_hi = (Word16)(L_tmp>>16);
+ y1_lo = (Word16)((L_tmp & 0xffff)>>1);
+
+ /* signal is divided by 16 to avoid overflow in energy computation */
+ *signal++ = (L_tmp + 0x8000) >> 16;
+ }while(--num !=0);
+
+ *mem-- = x1;
+ *mem-- = x0;
+ *mem-- = y1_lo;
+ *mem-- = y1_hi;
+ *mem-- = y2_lo;
+ *mem = y2_hi;
+ return;
+}
+
+
+
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