73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
//
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// Created by WolverinDEV on 28/03/2021.
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//
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#include <cmath>
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#include <algorithm>
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#include <cstring>
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#include "AudioVolume.h"
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using namespace tc;
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/* technique based on http://www.vttoth.com/CMS/index.php/technical-notes/68 */
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inline float merge_ab(float a, float b, float n) {
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/*
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* Form: A,B := [0;n]
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* IF A <= n/2 AND B <= N/2
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* Z = (2 * A * B) / n
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* ELSE
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* Z = 2(A + B) - (2/n) * A * B - n
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*
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* For a range from 0 to 2: Z = 2(A + B) - AB - 2
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*/
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auto half_n = n / 2;
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auto inv_half_n = 1 / half_n;
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if(a < half_n && b < half_n) {
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return inv_half_n * a * b;
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}
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return 2 * (a + b) - inv_half_n * a * b - n;
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}
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constexpr static auto kMaxChannelCount{32};
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float audio::audio_buffer_level(const float *buffer, size_t channel_count, size_t sample_count) {
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/*
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* TODO: May more like this:
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* https://source.chromium.org/chromium/chromium/src/+/master:third_party/webrtc/modules/audio_processing/rms_level.cc;l=30;drc=c6366b7101f99520b9203a884665e3d069523a6b;bpv=1;bpt=1
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*/
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if(channel_count > kMaxChannelCount) {
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return 0;
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}
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long double square_buffer[kMaxChannelCount];
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memset(square_buffer, 0, sizeof(long double) * kMaxChannelCount);
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auto buffer_ptr = buffer;
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for(size_t sample{0}; sample < sample_count; sample++) {
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for(size_t channel{0}; channel < channel_count; channel++) {
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auto value = *buffer_ptr++;
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square_buffer[channel] += value * value;
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}
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}
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float result{0};
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for(size_t channel{0}; channel < channel_count; channel++) {
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long double rms = sqrtl(square_buffer[channel] / (long double) sample_count);
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auto db = (long double) 20 * (log(rms) / log(10));
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db = std::max((long double) -192, std::min(db, (long double) 0));
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auto percentage = (float) (100 + (db * 1.92f));
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auto channel_value = std::clamp(percentage, 0.f, 100.f);
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if(channel == 0) {
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result = channel_value;
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} else {
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result = merge_ab(result, channel_value, 100);
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}
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}
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return result;
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} |