generate_wave_table.c

/*
 * 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
 */

#include <stdint.h>
#include "libavutil/avassert.h"
#include "avfilter.h"
#include "generate_wave_table.h"

void ff_generate_wave_table(enum WaveType wave_type,
                            enum AVSampleFormat sample_fmt,
                            void *table, int table_size,
                            double min, double max, double phase)
{
    uint32_t i, phase_offset = phase / M_PI / 2 * table_size + 0.5;

    for (i = 0; i < table_size; i++) {
        uint32_t point = (i + phase_offset) % table_size;
        double d;

        switch (wave_type) {
        case WAVE_SIN:
            d = (sin((double)point / table_size * 2 * M_PI) + 1) / 2;
            break;
        case WAVE_TRI:
            d = (double)point * 2 / table_size;
            switch (4 * point / table_size) {
            case 0: d = d + 0.5; break;
            case 1:
            case 2: d = 1.5 - d; break;
            case 3: d = d - 1.5; break;
            }
            break;
        default:
            av_assert0(0);
        }

        d  = d * (max - min) + min;
        switch (sample_fmt) {
        case AV_SAMPLE_FMT_FLT: {
            float *fp = (float *)table;
            *fp++ = (float)d;
            table = fp;
            continue; }
        case AV_SAMPLE_FMT_DBL: {
            double *dp = (double *)table;
            *dp++ = d;
            table = dp;
            continue; }
        }

        d += d < 0 ? -0.5 : 0.5;
        switch (sample_fmt) {
        case AV_SAMPLE_FMT_S16: {
            int16_t *sp = table;
            *sp++ = (int16_t)d;
            table = sp;
            continue; }
        case AV_SAMPLE_FMT_S32: {
            int32_t *ip = table;
            *ip++ = (int32_t)d;
            table = ip;
            continue; }
        default:
            av_assert0(0);
        }
    }
}