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New crossfeed algorithm for Rockbox: "Meier" crossfeed

Browse source 
Emulates the basic "Meier" crossfeed (2 capacitors, 3 resistors)
as discussed in
http://www.meier-audio.homepage.t-online.de/passivefilter.htm

This crossfeed blends a bit of low-pass filtered L signal into
the R signal (and vice versa) while adding about 300 us delay
to the crossfed-signal. A difference with the crossfeed already
present in rockbox, is that this algorithm keeps the total
spectrum flat (the one currently in rockbox accentuates
low-frequency signals, making it sound a bit muffled).

This implementation is quite lightweight, just 3 multiplies per
left-right pair of samples. Has a default C implementation and
optimized assembly versions for ARM and Coldfire.

The crossfeed effect is quite subtle and is noticeable mostly
one albums that have very strong left-right separation (e.g.
one instrument only on the left, another only on the right).

In the user interface, the new crossfeed option appears as
"Meier" and is not configureable. The existing crossfeed is
renamed to "Custom" as it allows itself to be customised.

There is no entry for the user manual yet.

Change-Id: Iaa100616fe0fcd7e16f08cdb9a7f41501973eee1
This commit is contained in:
Bertrik Sikken 2012-05-01 03:58:27 -04:00 committed by Thomas Martitz
parent 08f5224b1b
commit afc96087f8
11 changed files with 259 additions and 27 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
apps/lang/english.lang
View file

@ -13052,3 +13052,37 @@
*: "Western European"
</voice>
</phrase>
<phrase>
id: LANG_CROSSFEED_MEIER
desc: in sound settings
user: core
<source>
*: none
swcodec: "Simple (Meier)"
</source>
<dest>
*: none
swcodec: "Simple (Meier)"
</dest>
<voice>
*: none
swcodec: "Simple"
</voice>
</phrase>
<phrase>
id: LANG_CROSSFEED_CUSTOM
desc: in sound settings
user: core
<source>
*: none
swcodec: "Custom"
</source>
<dest>
*: none
swcodec: "Custom"
</dest>
<voice>
*: none
swcodec: "Custom"
</voice>
</phrase>

2
apps/plugin.c
View file

@ -565,7 +565,7 @@ static const struct plugin_api rockbox_api = {
audio_set_output_source,
audio_set_input_source,
#endif
dsp_crossfeed_enable,
dsp_set_crossfeed_type ,
dsp_eq_enable,
dsp_dither_enable,
#ifdef HAVE_PITCHCONTROL

2
apps/plugin.h
View file

@ -682,7 +682,7 @@ struct plugin_api {
void (*audio_set_output_source)(int monitor);
void (*audio_set_input_source)(int source, unsigned flags);
#endif
void (*dsp_crossfeed_enable)(bool enable);
void (*dsp_set_crossfeed_type)(int type);
void (*dsp_eq_enable)(bool enable);
void (*dsp_dither_enable)(bool enable);
#ifdef HAVE_PITCHCONTROL

5
apps/plugins/mpegplayer/mpeg_settings.c
View file

@ -457,8 +457,9 @@ static void sync_audio_setting(int setting, bool global)
break;
case MPEG_AUDIO_CROSSFEED:
rb->dsp_crossfeed_enable((global || settings.crossfeed) ?
rb->global_settings->crossfeed : false);
rb->dsp_set_crossfeed_type((global || settings.crossfeed) ?
rb->global_settings->crossfeed :
CROSSFEED_TYPE_NONE);
break;
case MPEG_AUDIO_EQUALIZER:

2
apps/settings.c
View file

@ -979,7 +979,7 @@ void settings_apply(bool read_disk)
audio_set_crossfade(global_settings.crossfade);
#endif
replaygain_update();
dsp_crossfeed_enable(global_settings.crossfeed);
dsp_set_crossfeed_type(global_settings.crossfeed);
dsp_set_crossfeed_direct_gain(global_settings.crossfeed_direct_gain);
dsp_set_crossfeed_cross_params(global_settings.crossfeed_cross_gain,
global_settings.crossfeed_hf_attenuation,

2
apps/settings.h
View file

@ -325,7 +325,7 @@ struct user_settings
struct replaygain_settings replaygain_settings;
/* Crossfeed */
bool crossfeed; /* enable crossfeed */
int crossfeed; /* crossfeed type */
unsigned int crossfeed_direct_gain; /* dB x 10 */
unsigned int crossfeed_cross_gain; /* dB x 10 */
unsigned int crossfeed_hf_attenuation; /* dB x 10 */

6
apps/settings_list.c
View file

@ -1402,8 +1402,10 @@ const struct settings_list settings[] = {
#endif
/* crossfeed */
OFFON_SETTING(F_SOUNDSETTING, crossfeed, LANG_CROSSFEED, false,
"crossfeed", dsp_crossfeed_enable),
CHOICE_SETTING(F_SOUNDSETTING, crossfeed, LANG_CROSSFEED, 0,"crossfeed",
"off,meier,custom", dsp_set_crossfeed_type, 3,
ID2P(LANG_OFF), ID2P(LANG_CROSSFEED_MEIER),
ID2P(LANG_CROSSFEED_CUSTOM)),
INT_SETTING_NOWRAP(F_SOUNDSETTING, crossfeed_direct_gain,
LANG_CROSSFEED_DIRECT_GAIN, -15,
"crossfeed direct gain", UNIT_DB, -60, 0, 5,

133
lib/rbcodec/dsp/crossfeed.c
View file

@ -8,6 +8,7 @@
* $Id$
*
* Copyright (C) 2006 Thom Johansen
* Copyright (C) 2010 Bertrik Sikken
* Copyright (C) 2012 Michael Sevakis
*
* This program is free software; you can redistribute it and/or
@ -31,7 +32,11 @@
#include <string.h>
/* Implemented here or in target assembly code */
void crossfeed_process(struct dsp_proc_entry *this, struct dsp_buffer **buf_p);
void crossfeed_process(struct dsp_proc_entry *this,
struct dsp_buffer **buf_p);
void crossfeed_meier_process(struct dsp_proc_entry *this,
struct dsp_buffer **buf_p);
/**
* Applies crossfeed to the stereo signal.
@ -46,20 +51,44 @@ static struct crossfeed_state
{
int32_t gain; /* 00h: Direct path gain */
int32_t coefs[3]; /* 04h: Coefficients for the shelving filter */
int32_t history[4]; /* 10h: Format is x[n - 1], y[n - 1] (L + R) */
int32_t delay[13*2]; /* 20h: Delay line buffer (L + R interleaved) */
union
{
struct /* 10h: Data for meier crossfeed */
{
int32_t vcl;
int32_t vcr;
int32_t vdiff;
int32_t coef1;
int32_t coef2;
};
struct /* 10h: Data for custom crossfeed */
{
int32_t history[4]; /* 10h: Format is x[n - 1], y[n - 1] (L + R) */
int32_t delay[13*2];/* 20h: Delay line buffer (L + R interleaved) */
};
};
int32_t *index; /* 88h: Current pointer into the delay line */
struct dsp_config *dsp; /* 8ch: Current DSP */
/* 90h */
} crossfeed_state IBSS_ATTR;
static int crossfeed_type = CROSSFEED_TYPE_NONE;
/* Discard the sample histories */
static void crossfeed_flush(struct dsp_proc_entry *this)
{
struct crossfeed_state *state = (void *)this->data;
memset(state->history, 0, sizeof (state->history));
memset(state->delay, 0, sizeof (state->delay));
state->index = state->delay;
if (crossfeed_type == CROSSFEED_TYPE_CUSTOM)
{
memset(state->history, 0,
sizeof (state->history) + sizeof (state->delay));
state->index = state->delay;
}
else
{
state->vcl = state->vcr = state->vdiff = 0;
}
}
@ -74,30 +103,48 @@ static void crossfeed_process_new_format(struct dsp_proc_entry *this,
DSP_PRINT_FORMAT(DSP_PROC_CROSSFEED, DSP_PROC_CROSSFEED, buf->format);
bool was_active = dsp_proc_active(state->dsp, DSP_PROC_CROSSFEED);
bool active = buf->format.num_channels >= 2;
dsp_proc_activate(state->dsp, DSP_PROC_CROSSFEED, active);
if (!active)
{
/* Can't do this. Sleep until next change */
crossfeed_flush(this);
DEBUGF(" DSP_PROC_CROSSFEED- deactivated\n");
return;
}
/* Switch to the real function and call it once */
this->process[0] = crossfeed_process;
dsp_proc_fn_type fn = crossfeed_process;
if (crossfeed_type != CROSSFEED_TYPE_CUSTOM)
{
/* 1 / (F.Rforward.C) */
state->coef1 = (0x7fffffff / NATIVE_FREQUENCY) * 2128;
/* 1 / (F.Rcross.C) */
state->coef2 = (0x7fffffff / NATIVE_FREQUENCY) * 1000;
fn = crossfeed_meier_process;
}
if (!was_active || this->process[0] != fn)
{
crossfeed_flush(this); /* Going online or actual type change */
this->process[0] = fn; /* Set real function */
}
/* Call it once */
dsp_proc_call(this, buf_p, (unsigned)buf->format.changed - 1);
}
/* Enable or disable the crossfeed */
void dsp_crossfeed_enable(bool enable)
/* Set the type of crossfeed to use */
void dsp_set_crossfeed_type(int type)
{
if (enable != !crossfeed_state.dsp)
return;
if (type == crossfeed_type)
return; /* No change */
crossfeed_type = type;
struct dsp_config *dsp = dsp_get_config(CODEC_IDX_AUDIO);
dsp_proc_enable(dsp, DSP_PROC_CROSSFEED, enable);
dsp_proc_enable(dsp, DSP_PROC_CROSSFEED, type != CROSSFEED_TYPE_NONE);
}
/* Set the gain of the dry mix */
@ -182,6 +229,50 @@ void crossfeed_process(struct dsp_proc_entry *this, struct dsp_buffer **buf_p)
}
#endif /* CPU */
#if !defined(CPU_COLDFIRE) && !defined(CPU_ARM)
/**
* Implementation of the "simple" passive crossfeed circuit by Jan Meier.
* See also: http://www.meier-audio.homepage.t-online.de/passivefilter.htm
*/
void crossfeed_meier_process(struct dsp_proc_entry *this,
struct dsp_buffer **buf_p)
{
struct dsp_buffer *buf = *buf_p;
/* Get filter state */
struct crossfeed_state *state = (struct crossfeed_state *)this->data;
int32_t vcl = state->vcl;
int32_t vcr = state->vcr;
int32_t vdiff = state->vdiff;
int32_t coef1 = state->coef1;
int32_t coef2 = state->coef2;
int count = buf->remcount;
for (int i = 0; i < count; i++)
{
/* Calculate new output */
int32_t lout = buf->p32[0][i] + vcl;
int32_t rout = buf->p32[1][i] + vcr;
buf->p32[0][i] = lout;
buf->p32[1][i] = rout;
/* Update filter state */
int32_t common = FRACMUL(vdiff, coef2);
vcl -= FRACMUL(vcl, coef1) + common;
vcr -= FRACMUL(vcr, coef1) - common;
vdiff = lout - rout;
}
/* Store filter state */
state->vcl = vcl;
state->vcr = vcr;
state->vdiff = vdiff;
}
#endif /* CPU */
/* DSP message hook */
static intptr_t crossfeed_configure(struct dsp_proc_entry *this,
struct dsp_config *dsp,
@ -191,11 +282,19 @@ static intptr_t crossfeed_configure(struct dsp_proc_entry *this,
switch (setting)
{
case DSP_PROC_INIT:
this->data = (intptr_t)&crossfeed_state;
if (value == 0)
{
/* New object */
this->data = (intptr_t)&crossfeed_state;
this->process[1] = crossfeed_process_new_format;
((struct crossfeed_state *)this->data)->dsp = dsp;
}
/* Force format change call each time */
this->process[0] = crossfeed_process_new_format;
this->process[1] = crossfeed_process_new_format;
((struct crossfeed_state *)this->data)->dsp = dsp;
dsp_proc_activate(dsp, DSP_PROC_CROSSFEED, true);
break;
case DSP_FLUSH:
crossfeed_flush(this);
break;

9
lib/rbcodec/dsp/crossfeed.h
View file

@ -21,7 +21,14 @@
#ifndef CROSSFEED_H
#define CROSSFEED_H
void dsp_crossfeed_enable(bool enable);
enum crossfeed_type
{
CROSSFEED_TYPE_NONE,
CROSSFEED_TYPE_MEIER,
CROSSFEED_TYPE_CUSTOM,
};
void dsp_set_crossfeed_type(int type);
void dsp_set_crossfeed_direct_gain(int gain);
void dsp_set_crossfeed_cross_params(long lf_gain, long hf_gain, long cutoff);

44
lib/rbcodec/dsp/dsp_arm.S
View file

@ -8,6 +8,8 @@
* $Id$
*
* Copyright (C) 2006-2007 Thom Johansen
* Copyright (C) 2010 Bertrik Sikken
* Copyright (C) 2012 Michael Sevakis
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -246,6 +248,48 @@ crossfeed_process:
ldmpc regs=r4-r11
.size crossfeed_process, .-crossfeed_process
/****************************************************************************
* void crossfeed_meier_process(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global crossfeed_meier_process
crossfeed_meier_process:
@ input: r0 = this, r1 = buf_p
ldr r1, [r1] @ r1 = buf = *buf_p;
ldr r0, [r0] @ r0 = this->data = &crossfeed_state
stmfd sp!, { r4-r10, lr } @ stack non-volatile context
ldmia r1, { r1-r3 } @ r1 = buf->remcout, r2=p32[0], r3=p32[1]
add r0, r0, #16 @ r0 = &state->vcl
ldmia r0, { r4-r8 } @ r4 = vcl, r5 = vcr, r6 = vdiff
@ r7 = coef1, r8 = coef2
.cfm_loop:
ldr r12, [r2] @ r12 = lout
ldr r14, [r3] @ r14 = rout
smull r9, r10, r8, r6 @ r9, r10 = common = coef2*vdiff
add r12, r12, r4 @ lout += vcl
add r14, r14, r5 @ rout += vcr
sub r6, r12, r14 @ r6 = vdiff = lout - rout
str r12, [r2], #4 @ store left channel
str r14, [r3], #4 @ store right channel
rsbs r12, r9, #0 @ r12 = -common (lo)
rsc r14, r10, #0 @ r14 = -common (hi)
smlal r9, r10, r7, r4 @ r9, r10 = res1 = coef1*vcl + common
smlal r12, r14, r7, r5 @ r12, r14 = res2 = coef1*vcr - common
subs r1, r1, #1 @ count--
mov r9, r9, lsr #31 @ r9 = convert res1 to s0.31
orr r9, r9, r10, asl #1 @ .
mov r12, r12, lsr #31 @ r12 = convert res2 to s0.31
orr r12, r12, r14, asl #1 @ .
sub r4, r4, r9 @ r4 = vcl -= res1
sub r5, r5, r12 @ r5 = vcr -= res2
bgt .cfm_loop @ more samples?
stmia r0, { r4-r6 } @ save vcl, vcr, vdiff
ldmpc regs=r4-r10 @ restore non-volatile context, return
.size crossfeed_meier_process, .-crossfeed_meier_process
/****************************************************************************
* int lin_resample_resample(struct resample_data *data,
* struct dsp_buffer *src,

47
lib/rbcodec/dsp/dsp_cf.S
View file

@ -8,7 +8,8 @@
* $Id$
*
* Copyright (C) 2006 Thom Johansen
* Portions Copyright (C) 2007 Michael Sevakis
* Copyright (C) 2007, 2012 Michael Sevakis
* Copyright (C) 2010 Bertrik Sikken
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -133,6 +134,50 @@ crossfeed_process:
rts |
.size crossfeed_process,.-crossfeed_process
/****************************************************************************
* void crossfeed_meier_process(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global crossfeed_meier_process
crossfeed_meier_process:
| input: 4(sp) = this, 8(sp) = buf_p
movem.l 4(%sp), %a0-%a1 | %a0 = this, %a1 = buf_p
lea.l -24(%sp), %sp | save non-volatiles
movem.l %d2-%d6/%a2, (%sp) | .
move.l (%a0), %a0 | %a0 = &this->data = &crossfeed_state
move.l (%a1), %a1 | %a1 = buf = *buf_p
movem.l 16(%a0), %d1-%d5 | %d1 = vcl, %d2 = vcr, %d3 = vdiff,
| %d4 = coef1, %d5 = coef2
movem.l (%a1), %d0/%a1-%a2 | %d0 = count = buf->remcount
| %a1 = p32[0], %a2 = p32[1]
| Register usage in loop:
| %d0 = count, %d1 = vcl, %d2 = vcr, %d3 = vdiff/lout,
| %d4 = coef1, %d5 = coef2, %d6 = rout/scratch
| %a1 = p32[0], %a2 = p32[1]
10: | loop
mac.l %d5, %d3, %acc0 | %acc0 = common = coef2*vdiff
move.l %acc0, %acc1 | copy common
mac.l %d4, %d1, (%a1), %d3, %acc0 | %acc0 += coef1*vcl, %d3 = lout
msac.l %d4, %d2, (%a2), %d6, %acc1 | %acc1 -= coef1*vcr, %d6 = rout
add.l %d1, %d3 | lout += vcl
add.l %d2, %d6 | rout += vcr
move.l %d3, (%a1)+ | store left channel, pos inc
move.l %d6, (%a2)+ | store right channel, pos inc
sub.l %d6, %d3 | vdiff = lout - rout
movclr.l %acc0, %d6 | %d4 = fetch res1 in s0.31
sub.l %d6, %d1 | vcl -= res1
movclr.l %acc1, %d6 | %d5 = fetch -res2 in s0.31
add.l %d6, %d2 | vcr += -res2
subq.l #1, %d0 | count--
bgt 10b | loop | more samples?
|
movem.l %d1-%d3, 16(%a0) | save vcl, vcr, vdiff
movem.l (%sp), %d2-%d6/%a2 | restore non-volatiles
lea.l 24(%sp), %sp | .
rts |
.size crossfeed_meier_process, .-crossfeed_meier_process
/****************************************************************************
* int lin_resample_resample(struct resample_data *data,
* struct dsp_buffer *src,