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audioconvert: add LFE filter

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Use a lowpass filter to generate LFE from the stereo channels.
This commit is contained in:
Wim Taymans 2021-03-09 17:23:43 +01:00
parent e51cc5b537
commit 14e8073d18
8 changed files with 261 additions and 0 deletions
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58
spa/plugins/audioconvert/crossover.c Normal file
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@ -0,0 +1,58 @@
/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "crossover.h"
void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq)
{
biquad_set(&lr4->bq, type, freq);
lr4->x1 = 0;
lr4->x2 = 0;
lr4->y1 = 0;
lr4->y2 = 0;
lr4->z1 = 0;
lr4->z2 = 0;
}
void lr4_process(struct lr4 *lr4, float *data, int samples)
{
float lx1 = lr4->x1;
float lx2 = lr4->x2;
float ly1 = lr4->y1;
float ly2 = lr4->y2;
float lz1 = lr4->z1;
float lz2 = lr4->z2;
float lb0 = lr4->bq.b0;
float lb1 = lr4->bq.b1;
float lb2 = lr4->bq.b2;
float la1 = lr4->bq.a1;
float la2 = lr4->bq.a2;
int i;
for (i = 0; i < samples; i++) {
float x, y, z;
x = data[i];
y = lb0*x + lb1*lx1 + lb2*lx2 - la1*ly1 - la2*ly2;
z = lb0*y + lb1*ly1 + lb2*ly2 - la1*lz1 - la2*lz2;
lx2 = lx1;
lx1 = x;
ly2 = ly1;
ly1 = y;
lz2 = lz1;
lz1 = z;
data[i] = z;
}
lr4->x1 = lx1;
lr4->x2 = lx2;
lr4->y1 = ly1;
lr4->y2 = ly2;
lr4->z1 = lz1;
lr4->z2 = lz2;
}