rockbox/lib/rbcodec/dsp/crossfeed.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * 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
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "rbcodecconfig.h"
#include "fixedpoint.h"
#include "fracmul.h"
#include "replaygain.h"
#include "dsp_proc_entry.h"
#include "dsp_filter.h"
#include "crossfeed.h"
#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_meier_process(struct dsp_proc_entry *this,
                             struct dsp_buffer **buf_p);


/**
 * Applies crossfeed to the stereo signal.
 *
 * Crossfeed is a process where listening over speakers is simulated. This
 * is good for old hard panned stereo records, which might be quite fatiguing
 * to listen to on headphones with no crossfeed.
 */

/* Crossfeed */
static struct crossfeed_state
{
    int32_t gain;           /* 00h: Direct path gain */
    int32_t coefs[3];       /* 04h: Coefficients for the shelving filter */
    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 */
                            /* 8ch */
} 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;

    if (crossfeed_type != CROSSFEED_TYPE_CUSTOM)
    {
        state->vcl = state->vcr = state->vdiff = 0;
    }
    else
    {
        memset(state->history, 0,
            sizeof (state->history) + sizeof (state->delay));
        state->index = state->delay;
    }
}


/** DSP interface **/

/* Set the type of crossfeed to use */
void dsp_set_crossfeed_type(int type)
{
    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, type != CROSSFEED_TYPE_NONE);
}

/* Set the gain of the dry mix */
void dsp_set_crossfeed_direct_gain(int gain)
{
    uint32_t gain32 = get_replaygain_int(gain * 10);
    crossfeed_state.gain =
        gain32 >= (0x80000000ul >> 7) ? 0x7ffffffful: (gain32 << 7);
}

/* Both gains should be below 0 dB */
void dsp_set_crossfeed_cross_params(long lf_gain, long hf_gain, long cutoff)
{
    int32_t *c = crossfeed_state.coefs;
    long scaler = get_replaygain_int(lf_gain * 10) << 7;

    cutoff = 0xffffffff / NATIVE_FREQUENCY * cutoff;
    hf_gain -= lf_gain;
    /* Divide cutoff by sqrt(10^(hf_gain/20)) to place cutoff at the -3 dB
     * point instead of shelf midpoint. This is for compatibility with the old
     * crossfeed shelf filter and should be removed if crossfeed settings are
     * ever made incompatible for any other good reason.
     */
    cutoff = fp_div(cutoff, get_replaygain_int(hf_gain*5), 24);
    filter_shelf_coefs(cutoff, hf_gain, false, c);
    /* Scale coefs by LF gain and shift them to s0.31 format. We have no gains
     * over 1 and can do this safely
     */
    c[0] = FRACMUL_SHL(c[0], scaler, 4);
    c[1] = FRACMUL_SHL(c[1], scaler, 4);
    c[2] <<= 4;
}

#if !defined(CPU_COLDFIRE) && !defined(CPU_ARM)
/* Apply the crossfade to the buffer in place */
void crossfeed_process(struct dsp_proc_entry *this, struct dsp_buffer **buf_p)
{
    struct crossfeed_state *state = (void *)this->data;
    struct dsp_buffer *buf = *buf_p;
   
    int32_t *hist_l = &state->history[0];
    int32_t *hist_r = &state->history[2];
    int32_t *delay = state->delay;
    int32_t *coefs = &state->coefs[0];
    int32_t gain = state->gain;
    int32_t *di = state->index;

    int count = buf->remcount;

    for (int i = 0; i < count; i++)
    {
        int32_t left = buf->p32[0][i];
        int32_t right = buf->p32[1][i];

        /* Filter delayed sample from left speaker */
        int32_t acc = FRACMUL(*di, coefs[0]);
        acc += FRACMUL(hist_l[0], coefs[1]);
        acc += FRACMUL(hist_l[1], coefs[2]);
        /* Save filter history for left speaker */
        hist_l[1] = acc;
        hist_l[0] = *di;
        *di++ = left;
        /* Filter delayed sample from right speaker */
        acc = FRACMUL(*di, coefs[0]);
        acc += FRACMUL(hist_r[0], coefs[1]);
        acc += FRACMUL(hist_r[1], coefs[2]);
        /* Save filter history for right speaker */
        hist_r[1] = acc;
        hist_r[0] = *di;
        *di++ = right;
        /* Now add the attenuated direct sound and write to outputs */
        buf->p32[0][i] = FRACMUL(left, gain) + hist_r[1];
        buf->p32[1][i] = FRACMUL(right, gain) + hist_l[1];

        /* Wrap delay line index if bigger than delay line size */
        if (di >= delay + 13*2)
            di = delay;
    }

    /* Write back local copies of data we've modified */
    state->index = di;
}
#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 */

/* Update the processing function according to crossfeed type */
static void update_process_fn(struct dsp_proc_entry *this,
                              struct dsp_config *dsp)
{
    struct crossfeed_state *state = (struct crossfeed_state *)this->data;
    dsp_proc_fn_type fn = crossfeed_process;

    if (crossfeed_type != CROSSFEED_TYPE_CUSTOM)
    {
        /* Set up for Meier */
        /* 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 (this->process != fn)
    {
        this->process = fn;    /* Set proper function */
        if (dsp_proc_active(dsp, DSP_PROC_CROSSFEED))
            crossfeed_flush(this);
    }
}

/* Crossfeed boot/format change function */
static intptr_t crossfeed_new_format(struct dsp_proc_entry *this,
                                     struct dsp_config *dsp,
                                     struct sample_format *format)
{
    DSP_PRINT_FORMAT(DSP_PROC_CROSSFEED, format);

    bool was_active = dsp_proc_active(dsp, DSP_PROC_CROSSFEED);
    bool active = format->num_channels >= 2;
    dsp_proc_activate(dsp, DSP_PROC_CROSSFEED, active);

    if (active)
    {
        if (!was_active)
            crossfeed_flush(this); /* Going online */

        return PROC_NEW_FORMAT_OK;
    }

    /* Can't do this. Sleep until next change */
    DEBUGF("  DSP_PROC_CROSSFEED- deactivated\n");
    return PROC_NEW_FORMAT_DEACTIVATED;
}

/* DSP message hook */
static intptr_t crossfeed_configure(struct dsp_proc_entry *this,
                                    struct dsp_config *dsp,
                                    unsigned int setting,
                                    intptr_t value)
{
    intptr_t retval = 0;

    switch (setting)
    {
    case DSP_PROC_INIT:
        if (value == 0)
            this->data = (intptr_t)&crossfeed_state;

        update_process_fn(this, dsp);
        break;

    case DSP_FLUSH:
        crossfeed_flush(this);
        break;

    case DSP_PROC_NEW_FORMAT:
        retval = crossfeed_new_format(this, dsp,
                                      (struct sample_format *)value);
        break;
    }

    return retval;
}

/* Database entry */
DSP_PROC_DB_ENTRY(
    CROSSFEED,
    crossfeed_configure);