atrac.c

Go to the documentation of this file.

/*
 * common functions for the ATRAC family of decoders
 *
 * Copyright (c) 2006-2013 Maxim Poliakovski
 * Copyright (c) 2006-2008 Benjamin Larsson
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
/**
 * @file
 */
 
#include <math.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
 
#include "libavutil/thread.h"
 
#include "avcodec.h"
#include "atrac.h"
 
float ff_atrac_sf_table[64];
static float qmf_window[48];
 
static const float qmf_48tap_half[24] = {
   -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
    0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
    0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
   -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
   -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
   -0.043596379,   -0.099384367,   0.13207909,    0.46424159
};
 
static av_cold void atrac_generate_tables(void)
{
    /* Generate scale factors */
    for (int i = 0; i < 64; i++)
        ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
 
    /* Generate the QMF window. */
    for (int i = 0; i < 24; i++) {
        float s = qmf_48tap_half[i] * 2.0;
        qmf_window[i] = qmf_window[47 - i] = s;
    }
}
 
av_cold void ff_atrac_generate_tables(void)
{
    static AVOnce init_static_once = AV_ONCE_INIT;
    ff_thread_once(&init_static_once, atrac_generate_tables);
}
 
av_cold void ff_atrac_init_gain_compensation(AtracGCContext *gctx, int id2exp_offset,
                                             int loc_scale)
{
    int i;
 
    gctx->loc_scale     = loc_scale;
    gctx->loc_size      = 1 << loc_scale;
    gctx->id2exp_offset = id2exp_offset;
 
    /* Generate gain level table. */
    for (i = 0; i < 16; i++)
        gctx->gain_tab1[i] = powf(2.0, id2exp_offset - i);
 
    /* Generate gain interpolation table. */
    for (i = -15; i < 16; i++)
        gctx->gain_tab2[i + 15] = powf(2.0, -1.0f / gctx->loc_size * i);
}
 
void ff_atrac_gain_compensation(AtracGCContext *gctx, float *in, float *prev,
                                AtracGainInfo *gc_now, AtracGainInfo *gc_next,
                                int num_samples, float *out)
{
    float lev, gc_scale, gain_inc;
    int i, pos, lastpos;
 
    gc_scale = gc_next->num_points ? gctx->gain_tab1[gc_next->lev_code[0]]
                                   : 1.0f;
 
    if (!gc_now->num_points) {
        for (pos = 0; pos < num_samples; pos++)
            out[pos] = in[pos] * gc_scale + prev[pos];
    } else {
        pos = 0;
 
        for (i = 0; i < gc_now->num_points; i++) {
            lastpos = gc_now->loc_code[i] << gctx->loc_scale;
 
            lev = gctx->gain_tab1[gc_now->lev_code[i]];
            gain_inc = gctx->gain_tab2[(i + 1 < gc_now->num_points ? gc_now->lev_code[i + 1]
                                                                   : gctx->id2exp_offset) -
                                       gc_now->lev_code[i] + 15];
 
            /* apply constant gain level and overlap */
            for (; pos < lastpos; pos++)
                out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
 
            /* interpolate between two different gain levels */
            for (; pos < lastpos + gctx->loc_size; pos++) {
                out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
                lev *= gain_inc;
            }
        }
 
        for (; pos < num_samples; pos++)
            out[pos] = in[pos] * gc_scale + prev[pos];
    }
 
    /* copy the overlapping part into the delay buffer */
    memcpy(prev, &in[num_samples], num_samples * sizeof(float));
}
 
void ff_atrac_iqmf(float *inlo, float *inhi, unsigned int nIn, float *pOut,
                   float *delayBuf, float *temp)
{
    int   i, j;
    float   *p1, *p3;
 
    memcpy(temp, delayBuf, 46*sizeof(float));
 
    p3 = temp + 46;
 
    /* loop1 */
    for(i=0; i<nIn; i+=2){
        p3[2*i+0] = inlo[i  ] + inhi[i  ];
        p3[2*i+1] = inlo[i  ] - inhi[i  ];
        p3[2*i+2] = inlo[i+1] + inhi[i+1];
        p3[2*i+3] = inlo[i+1] - inhi[i+1];
    }
 
    /* loop2 */
    p1 = temp;
    for (j = nIn; j != 0; j--) {
        float s1 = 0.0;
        float s2 = 0.0;
 
        for (i = 0; i < 48; i += 2) {
            s1 += p1[i] * qmf_window[i];
            s2 += p1[i+1] * qmf_window[i+1];
        }
 
        pOut[0] = s2;
        pOut[1] = s1;
 
        p1 += 2;
        pOut += 2;
    }
 
    /* Update the delay buffer. */
    memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
}