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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//#define LOG_NDEBUG 0
#define LOG_TAG "audio_utils_conversion"
#include <math.h>
#include <audio_utils/conversion.h>
#include <utils/Log.h>
#include <audio_utils/limiter.h>
// TODO: Speed up for special case of 2 channels?
void mono_blend(void *buf, audio_format_t format, size_t channelCount, size_t frames, bool limit) {
if (channelCount < 2) {
return;
}
switch (format) {
case AUDIO_FORMAT_PCM_16_BIT: {
int16_t *out = (int16_t *)buf;
for (size_t i = 0; i < frames; ++i) {
const int16_t *in = out;
int accum = 0;
for (size_t j = 0; j < channelCount; ++j) {
accum += *in++;
}
accum /= channelCount; // round to 0
for (size_t j = 0; j < channelCount; ++j) {
*out++ = accum;
}
}
} break;
case AUDIO_FORMAT_PCM_FLOAT: {
float *out = (float *)buf;
const float recipdiv = 1. / channelCount;
for (size_t i = 0; i < frames; ++i) {
const float *in = out;
float accum = 0;
for (size_t j = 0; j < channelCount; ++j) {
accum += *in++;
}
if (limit && channelCount == 2) {
accum = limiter(accum * M_SQRT1_2);
} else {
accum *= recipdiv;
}
for (size_t j = 0; j < channelCount; ++j) {
*out++ = accum;
}
}
} break;
default:
ALOGE("mono_blend: invalid format %d", format);
break;
}
}