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/***
This file is part of PulseAudio.
Copyright 2014 David Henningsson, Canonical Ltd.
PulseAudio 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.
PulseAudio 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
General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "lfe-filter.h"
#include <pulse/xmalloc.h>
#include <pulsecore/filter/biquad.h>
#include <pulsecore/filter/crossover.h>
/* An LR4 filter, implemented as a chain of two Butterworth filters.
Currently the channel map is fixed so that a highpass filter is applied to all
channels except for the LFE channel, where a lowpass filter is applied.
This works well for e g stereo to 2.1/5.1/7.1 scenarios, where the remap engine
has calculated the LFE channel to be the average of all source channels.
*/
struct pa_lfe_filter {
float crossover;
pa_channel_map cm;
pa_sample_spec ss;
bool active;
struct lr4 lr4[PA_CHANNELS_MAX];
};
pa_lfe_filter_t * pa_lfe_filter_new(const pa_sample_spec* ss, const pa_channel_map* cm, float crossover_freq) {
pa_lfe_filter_t *f = pa_xnew0(struct pa_lfe_filter, 1);
f->crossover = crossover_freq;
f->cm = *cm;
f->ss = *ss;
pa_lfe_filter_update_rate(f, ss->rate);
return f;
}
void pa_lfe_filter_free(pa_lfe_filter_t *f) {
pa_xfree(f);
}
void pa_lfe_filter_reset(pa_lfe_filter_t *f) {
pa_lfe_filter_update_rate(f, f->ss.rate);
}
pa_memchunk * pa_lfe_filter_process(pa_lfe_filter_t *f, pa_memchunk *buf) {
int samples = buf->length / pa_frame_size(&f->ss);
if (!f->active)
return buf;
if (f->ss.format == PA_SAMPLE_FLOAT32NE) {
int i;
float *data = pa_memblock_acquire_chunk(buf);
for (i = 0; i < f->cm.channels; i++)
lr4_process_float32(&f->lr4[i], samples, f->cm.channels, &data[i], &data[i]);
pa_memblock_release(buf->memblock);
}
else if (f->ss.format == PA_SAMPLE_S16NE) {
int i;
short *data = pa_memblock_acquire_chunk(buf);
for (i = 0; i < f->cm.channels; i++)
lr4_process_s16(&f->lr4[i], samples, f->cm.channels, &data[i], &data[i]);
pa_memblock_release(buf->memblock);
}
else pa_assert_not_reached();
return buf;
}
void pa_lfe_filter_update_rate(pa_lfe_filter_t *f, uint32_t new_rate) {
int i;
float biquad_freq = f->crossover / (new_rate / 2);
f->ss.rate = new_rate;
if (biquad_freq <= 0 || biquad_freq >= 1) {
pa_log_warn("Crossover frequency (%f) outside range for sample rate %d", f->crossover, new_rate);
f->active = false;
return;
}
for (i = 0; i < f->cm.channels; i++)
lr4_set(&f->lr4[i], f->cm.map[i] == PA_CHANNEL_POSITION_LFE ? BQ_LOWPASS : BQ_HIGHPASS, biquad_freq);
f->active = true;
}
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