69 lines
1.4 KiB
C++
69 lines
1.4 KiB
C++
#include <psemek/audio/effect/fade_out.hpp>
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#include <psemek/audio/constants.hpp>
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#include <cmath>
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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 fade_out_impl
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: stream
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{
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fade_out_impl(stream_ptr stream, float length, float start)
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: stream_(std::move(stream))
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, length_(2 * std::round(length * frequency))
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, start_samples_(2 * std::round(start * frequency))
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{}
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std::optional<std::size_t> length() const override
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{
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// TODO: compute fade_out length using the number of samples already played
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return stream_->length();
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}
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std::size_t read(float * data, std::size_t sample_count) override
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{
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if (current_ >= length_)
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return 0;
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auto result = stream_->read(data, sample_count);
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if (result <= start_samples_)
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{
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start_samples_ -= result;
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}
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else
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{
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for (std::size_t i = start_samples_; i < result; i += 2)
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{
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float m = static_cast<float>(length_ - std::min(current_, length_)) / length_;
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data[i + 0] *= m;
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data[i + 1] *= m;
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current_ += 2;
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}
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start_samples_ = 0;
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}
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return result;
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}
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private:
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stream_ptr stream_;
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std::size_t length_;
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std::size_t current_ = 0;
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std::size_t start_samples_;
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};
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}
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stream_ptr fade_out(stream_ptr stream, float length, float start)
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{
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return std::make_shared<fade_out_impl>(std::move(stream), length, start);
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}
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}
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