[pulseaudio-discuss] [PATCH 2/7] lfe-filter: Enable LFE filter in the resampler
David Henningsson
david.henningsson at canonical.com
Tue Feb 17 04:29:19 PST 2015
When enable-lfe-remixing is set, an LFE channel is present in the
resampler's destination channel map but not in the source channel map,
we insert a low-pass filter instead of just averaging the channels.
Other channels will get a high-pass filter.
In this patch, the crossover frequency is hardcoded to 120Hz (to be fixed
in later patches).
Note that in current state the LFE filter is
- not very optimised
- not rewind friendly (rewinding can cause audible artifacts)
Signed-off-by: David Henningsson <david.henningsson at canonical.com>
---
src/Makefile.am | 3 ++
src/pulsecore/filter/crossover.c | 85 ++++++++++++++++++++++++++++++-
src/pulsecore/filter/crossover.h | 6 +++
src/pulsecore/filter/lfe-filter.c | 103 ++++++++++++++++++++++++++++++++++++++
src/pulsecore/filter/lfe-filter.h | 38 ++++++++++++++
src/pulsecore/resampler.c | 34 +++++++++++--
src/pulsecore/resampler.h | 3 ++
7 files changed, 267 insertions(+), 5 deletions(-)
create mode 100644 src/pulsecore/filter/lfe-filter.c
create mode 100644 src/pulsecore/filter/lfe-filter.h
diff --git a/src/Makefile.am b/src/Makefile.am
index 67f8627..302c532 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -911,6 +911,9 @@ lib_LTLIBRARIES += libpulsecore- at PA_MAJORMINOR@.la
# Pure core stuff
libpulsecore_ at PA_MAJORMINOR@_la_SOURCES = \
+ pulsecore/filter/lfe-filter.c pulsecore/filter/lfe-filter.h \
+ pulsecore/filter/biquad.c pulsecore/filter/biquad.h \
+ pulsecore/filter/crossover.c pulsecore/filter/crossover.h \
pulsecore/asyncmsgq.c pulsecore/asyncmsgq.h \
pulsecore/asyncq.c pulsecore/asyncq.h \
pulsecore/auth-cookie.c pulsecore/auth-cookie.h \
diff --git a/src/pulsecore/filter/crossover.c b/src/pulsecore/filter/crossover.c
index 11a8c6e..6a817d4 100644
--- a/src/pulsecore/filter/crossover.c
+++ b/src/pulsecore/filter/crossover.c
@@ -3,10 +3,16 @@
* found in the LICENSE file.
*/
-#include "crossover.h"
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <pulsecore/macro.h>
+
#include "biquad.h"
+#include "crossover.h"
-static void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq)
+void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq)
{
struct biquad q;
biquad_set(&q, type, freq, 0, 0);
@@ -23,6 +29,81 @@ static void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq)
lr4->z2 = 0;
}
+void lr4_process_float32(struct lr4 *lr4, int samples, int channels, float *src, float *dest)
+{
+ 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->b0;
+ float lb1 = lr4->b1;
+ float lb2 = lr4->b2;
+ float la1 = lr4->a1;
+ float la2 = lr4->a2;
+
+ int i;
+ for (i = 0; i < samples; i += channels) {
+ float x, y, z;
+ x = src[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;
+ dest[i] = PA_CLAMP_UNLIKELY((int) z, -0x8000, 0x7fff);
+ }
+
+ lr4->x1 = lx1;
+ lr4->x2 = lx2;
+ lr4->y1 = ly1;
+ lr4->y2 = ly2;
+ lr4->z1 = lz1;
+ lr4->z2 = lz2;
+}
+
+void lr4_process_s16(struct lr4 *lr4, int samples, int channels, short *src, short *dest)
+{
+ 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->b0;
+ float lb1 = lr4->b1;
+ float lb2 = lr4->b2;
+ float la1 = lr4->a1;
+ float la2 = lr4->a2;
+
+ int i;
+ for (i = 0; i < samples; i += channels) {
+ float x, y, z;
+ x = src[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;
+ dest[i] = z;
+ }
+
+ lr4->x1 = lx1;
+ lr4->x2 = lx2;
+ lr4->y1 = ly1;
+ lr4->y2 = ly2;
+ lr4->z1 = lz1;
+ lr4->z2 = lz2;
+}
+
+
/* Split input data using two LR4 filters, put the result into the input array
* and another array.
*
diff --git a/src/pulsecore/filter/crossover.h b/src/pulsecore/filter/crossover.h
index 99a601c..a88f5b6 100644
--- a/src/pulsecore/filter/crossover.h
+++ b/src/pulsecore/filter/crossover.h
@@ -25,6 +25,12 @@ struct lr4 {
float z1, z2;
};
+void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq);
+
+void lr4_process_float32(struct lr4 *lr4, int samples, int channels, float *src, float *dest);
+void lr4_process_s16(struct lr4 *lr4, int samples, int channels, short *src, short *dest);
+
+
/* Three bands crossover filter:
*
* INPUT --+-- lp0 --+-- lp1 --+---> LOW (0)
diff --git a/src/pulsecore/filter/lfe-filter.c b/src/pulsecore/filter/lfe-filter.c
new file mode 100644
index 0000000..9b238fe
--- /dev/null
+++ b/src/pulsecore/filter/lfe-filter.c
@@ -0,0 +1,103 @@
+/***
+ 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, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ USA.
+***/
+
+#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_sample_size_of_format(f->ss.format);
+
+ 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;
+}
diff --git a/src/pulsecore/filter/lfe-filter.h b/src/pulsecore/filter/lfe-filter.h
new file mode 100644
index 0000000..25db8a0
--- /dev/null
+++ b/src/pulsecore/filter/lfe-filter.h
@@ -0,0 +1,38 @@
+#ifndef foolfefilterhfoo
+#define foolfefilterhfoo
+
+/***
+ 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, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ USA.
+***/
+
+#include <pulse/sample.h>
+#include <pulse/channelmap.h>
+#include <pulsecore/memchunk.h>
+
+
+typedef struct pa_lfe_filter pa_lfe_filter_t;
+
+pa_lfe_filter_t * pa_lfe_filter_new(const pa_sample_spec* ss, const pa_channel_map* cm, float crossover_freq);
+void pa_lfe_filter_free(pa_lfe_filter_t *);
+void pa_lfe_filter_reset(pa_lfe_filter_t *);
+pa_memchunk * pa_lfe_filter_process(pa_lfe_filter_t *filter, pa_memchunk *buf);
+void pa_lfe_filter_update_rate(pa_lfe_filter_t *, uint32_t new_rate);
+
+#endif
diff --git a/src/pulsecore/resampler.c b/src/pulsecore/resampler.c
index 0d7cc20..157671d 100644
--- a/src/pulsecore/resampler.c
+++ b/src/pulsecore/resampler.c
@@ -40,7 +40,7 @@ struct ffmpeg_data { /* data specific to ffmpeg */
static int copy_init(pa_resampler *r);
-static void setup_remap(const pa_resampler *r, pa_remap_t *m);
+static void setup_remap(const pa_resampler *r, pa_remap_t *m, bool *lfe_filter_required);
static void free_remap(pa_remap_t *m);
static int (* const init_table[])(pa_resampler *r) = {
@@ -324,6 +324,7 @@ pa_resampler* pa_resampler_new(
pa_resample_flags_t flags) {
pa_resampler *r = NULL;
+ bool lfe_filter_required = false;
pa_assert(pool);
pa_assert(a);
@@ -412,7 +413,15 @@ pa_resampler* pa_resampler_new(
/* set up the remap structure */
if (r->map_required)
- setup_remap(r, &r->remap);
+ setup_remap(r, &r->remap, &lfe_filter_required);
+
+ if (lfe_filter_required) {
+ pa_sample_spec wss = r->o_ss;
+ wss.format = r->work_format;
+ /* TODO: Temporary code that sets crossover freq to 120 Hz. This should be a parameter */
+ r->lfe_filter = pa_lfe_filter_new(&wss, &r->o_cm, 120.0f);
+ pa_log_debug(" lfe filter activated (LR4 type)");
+ }
/* initialize implementation */
if (init_table[method](r) < 0)
@@ -434,6 +443,9 @@ void pa_resampler_free(pa_resampler *r) {
else
pa_xfree(r->impl.data);
+ if (r->lfe_filter)
+ pa_lfe_filter_free(r->lfe_filter);
+
if (r->to_work_format_buf.memblock)
pa_memblock_unref(r->to_work_format_buf.memblock);
if (r->remap_buf.memblock)
@@ -472,6 +484,9 @@ void pa_resampler_set_output_rate(pa_resampler *r, uint32_t rate) {
r->o_ss.rate = rate;
r->impl.update_rates(r);
+
+ if (r->lfe_filter)
+ pa_lfe_filter_update_rate(r->lfe_filter, rate);
}
size_t pa_resampler_request(pa_resampler *r, size_t out_length) {
@@ -556,6 +571,9 @@ void pa_resampler_reset(pa_resampler *r) {
if (r->impl.reset)
r->impl.reset(r);
+ if (r->lfe_filter)
+ pa_lfe_filter_reset(r->lfe_filter);
+
*r->have_leftover = false;
}
@@ -756,7 +774,7 @@ static int front_rear_side(pa_channel_position_t p) {
return ON_OTHER;
}
-static void setup_remap(const pa_resampler *r, pa_remap_t *m) {
+static void setup_remap(const pa_resampler *r, pa_remap_t *m, bool *lfe_filter_required) {
unsigned oc, ic;
unsigned n_oc, n_ic;
bool ic_connected[PA_CHANNELS_MAX];
@@ -765,6 +783,7 @@ static void setup_remap(const pa_resampler *r, pa_remap_t *m) {
pa_assert(r);
pa_assert(m);
+ pa_assert(lfe_filter_required);
n_oc = r->o_ss.channels;
n_ic = r->i_ss.channels;
@@ -777,6 +796,7 @@ static void setup_remap(const pa_resampler *r, pa_remap_t *m) {
memset(m->map_table_i, 0, sizeof(m->map_table_i));
memset(ic_connected, 0, sizeof(ic_connected));
+ *lfe_filter_required = false;
if (r->flags & PA_RESAMPLER_NO_REMAP) {
for (oc = 0; oc < PA_MIN(n_ic, n_oc); oc++)
@@ -888,6 +908,9 @@ static void setup_remap(const pa_resampler *r, pa_remap_t *m) {
oc_connected = true;
ic_connected[ic] = true;
+
+ if (a == PA_CHANNEL_POSITION_MONO && on_lfe(b) && !(r->flags & PA_RESAMPLER_NO_LFE))
+ *lfe_filter_required = true;
}
else if (b == PA_CHANNEL_POSITION_MONO) {
m->map_table_f[oc][ic] = 1.0f / (float) n_ic;
@@ -970,6 +993,8 @@ static void setup_remap(const pa_resampler *r, pa_remap_t *m) {
/* Please note that a channel connected to LFE doesn't
* really count as connected. */
+
+ *lfe_filter_required = true;
}
}
}
@@ -1340,6 +1365,9 @@ void pa_resampler_run(pa_resampler *r, const pa_memchunk *in, pa_memchunk *out)
buf = remap_channels(r, buf);
}
+ if (r->lfe_filter)
+ buf = pa_lfe_filter_process(r->lfe_filter, buf);
+
if (buf->length) {
buf = convert_from_work_format(r, buf);
*out = *buf;
diff --git a/src/pulsecore/resampler.h b/src/pulsecore/resampler.h
index 4840a5e..45ad75a 100644
--- a/src/pulsecore/resampler.h
+++ b/src/pulsecore/resampler.h
@@ -26,6 +26,7 @@
#include <pulsecore/memchunk.h>
#include <pulsecore/sconv.h>
#include <pulsecore/remap.h>
+#include <pulsecore/filter/lfe-filter.h>
typedef struct pa_resampler pa_resampler;
typedef struct pa_resampler_impl pa_resampler_impl;
@@ -106,6 +107,8 @@ struct pa_resampler {
pa_remap_t remap;
bool map_required;
+ pa_lfe_filter_t *lfe_filter;
+
pa_resampler_impl impl;
};
--
1.9.1
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