87 lines
2.5 KiB
C++
87 lines
2.5 KiB
C++
#include <psemek/audio/effect/compressor.hpp>
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#include <psemek/audio/detail/smooth.hpp>
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#include <psemek/geom/math.hpp>
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#include <psemek/geom/interval.hpp>
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#include <psemek/geom/contains.hpp>
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namespace psemek::audio
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{
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namespace
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{
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struct compressor_impl
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: stream
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{
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compressor_impl(stream_ptr stream, float volume_threshold, float strength, float envelope_attack, float envelope_release, float knee)
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: stream_(std::move(stream))
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, volume_threshold_log_(std::log(volume_threshold))
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, strength_(strength)
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, envelope_attack_multiplier_(smoothness_to_multiplier(envelope_attack))
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, envelope_release_multiplier_(smoothness_to_multiplier(envelope_release))
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, knee_range_(geom::expand(geom::interval<float>::singleton(volume_threshold_log_), std::log(knee) * 0.5f))
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{}
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std::optional<std::size_t> length() const override
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{
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return stream_->length();
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}
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std::size_t read(util::span<float> samples) override
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{
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auto count = stream_->read(samples);
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for (std::size_t i = 0; i < count; i += 2)
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{
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float v = std::max(std::abs(samples[i]), std::abs(samples[i + 1]));
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float multiplier = (v > envelope_) ? envelope_attack_multiplier_ : envelope_release_multiplier_;
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envelope_ += (v - envelope_) * multiplier;
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float strength = strength_;
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float envelope_log = std::log(envelope_);
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if (geom::contains(knee_range_, envelope_log))
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strength *= geom::unlerp(knee_range_, envelope_log);
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float log_gain = strength * std::min(0.f, volume_threshold_log_ - envelope_log);
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float gain = std::exp(log_gain);
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samples[i + 0] *= gain;
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samples[i + 1] *= gain;
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}
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return count;
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}
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std::size_t played() const override
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{
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return stream_->played();
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}
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private:
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stream_ptr stream_;
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float volume_threshold_log_;
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float strength_;
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float envelope_attack_multiplier_;
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float envelope_release_multiplier_;
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geom::interval<float> knee_range_;
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float envelope_ = 0.f;
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};
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}
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stream_ptr compressor(stream_ptr stream, float volume_threshold, float strength, float envelope_attack, float envelope_release, float knee)
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{
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return std::make_shared<compressor_impl>(std::move(stream), volume_threshold, strength, envelope_attack, envelope_release, knee);
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}
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stream_ptr limiter(stream_ptr stream, float volume_threshold, float envelope_attack, float envelope_release, float knee)
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{
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return compressor(std::move(stream), volume_threshold, 1.f, envelope_attack, envelope_release, knee);
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}
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}
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