BackgroundAudioGain.h

/*
    BackgroundAudio
    Plays an audio file using IRQ driven decompression.  Main loop() writes
    data to the buffer but isn't blocked while playing
 
    Copyright (c) 2024 Earle F. Philhower, III <earlephilhower@yahoo.com>
 
    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 3 of the License, or
    (at your option) any later version.
 
    This program 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 General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#pragma once
#include <stdint.h>
 
static inline void ApplyGain(int16_t *samples, size_t count, int32_t gain) {
    // Default case, don't do anything
    if (gain == 1 << 16) {
        return;
    }
 
    if (gain > 1 << 16) { // May clip
        for (size_t i = 0; i < count; i++) {
            int32_t x = samples[i];
            x *= gain;
            x >>= 16;
            if (x < -32767) {
                x = -32767;
            } else if (x > 32767) {
                x = 32767;
            }
            samples[i] = x;
        }
    } else { // Can't clip, no need to check
        for (size_t i = 0; i < count; i++) {
            int32_t x = samples[i];
            x *= gain;
            x >>= 16;
            samples[i] = x;
        }
    }
}