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