mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-12 19:18:44 +02:00
91e192c3a0
Reviewed-by: Lynne <dev@lynne.ee> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
91 lines
2.6 KiB
C
91 lines
2.6 KiB
C
/*
|
|
* Opus encoder
|
|
* Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#ifndef AVCODEC_OPUSENC_UTILS_H
|
|
#define AVCODEC_OPUSENC_UTILS_H
|
|
|
|
#include <math.h>
|
|
#include <string.h>
|
|
|
|
#include "opus.h"
|
|
|
|
typedef struct FFBesselFilter {
|
|
float a[3];
|
|
float b[2];
|
|
float x[3];
|
|
float y[3];
|
|
} FFBesselFilter;
|
|
|
|
/* Fills the coefficients, returns 1 if filter will be unstable */
|
|
static inline int bessel_reinit(FFBesselFilter *s, float n, float f0, float fs,
|
|
int highpass)
|
|
{
|
|
int unstable;
|
|
float c, cfreq, w0, k1, k2;
|
|
|
|
if (!highpass) {
|
|
c = (1.0f/sqrtf(sqrtf(pow(2.0f, 1.0f/n) - 3.0f/4.0f) - 0.5f))/sqrtf(3.0f);
|
|
cfreq = c*f0/fs;
|
|
unstable = (cfreq <= 0.0f || cfreq >= 1.0f/4.0f);
|
|
} else {
|
|
c = sqrtf(3.0f)*sqrtf(sqrtf(pow(2.0f, 1.0f/n) - 3.0f/4.0f) - 0.5f);
|
|
cfreq = 0.5f - c*f0/fs;
|
|
unstable = (cfreq <= 3.0f/8.0f || cfreq >= 1.0f/2.0f);
|
|
}
|
|
|
|
w0 = tanf(M_PI*cfreq);
|
|
k1 = 3.0f * w0;
|
|
k2 = 3.0f * w0;
|
|
|
|
s->a[0] = k2/(1.0f + k1 + k2);
|
|
s->a[1] = 2.0f * s->a[0];
|
|
s->a[2] = s->a[0];
|
|
s->b[0] = 2.0f * s->a[0] * (1.0f/k2 - 1.0f);
|
|
s->b[1] = 1.0f - (s->a[0] + s->a[1] + s->a[2] + s->b[0]);
|
|
|
|
if (highpass) {
|
|
s->a[1] *= -1;
|
|
s->b[0] *= -1;
|
|
}
|
|
|
|
return unstable;
|
|
}
|
|
|
|
static inline int bessel_init(FFBesselFilter *s, float n, float f0, float fs,
|
|
int highpass)
|
|
{
|
|
memset(s, 0, sizeof(FFBesselFilter));
|
|
return bessel_reinit(s, n, f0, fs, highpass);
|
|
}
|
|
|
|
static inline float bessel_filter(FFBesselFilter *s, float x)
|
|
{
|
|
s->x[2] = s->x[1];
|
|
s->x[1] = s->x[0];
|
|
s->x[0] = x;
|
|
s->y[2] = s->y[1];
|
|
s->y[1] = s->y[0];
|
|
s->y[0] = s->a[0]*s->x[0] + s->a[1]*s->x[1] + s->a[2]*s->x[2] + s->b[0]*s->y[1] + s->b[1]*s->y[2];
|
|
return s->y[0];
|
|
}
|
|
|
|
#endif /* AVCODEC_OPUSENC_UTILS_H */
|