74 lines
1.4 KiB
C++
74 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, duration length, duration start)
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: stream_(std::move(stream))
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, length_(length)
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, start_(start)
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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 played() const override
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{
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return stream_->played();
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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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if (current_ >= length_.samples())
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return 0;
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auto result = stream_->read(samples);
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if (result <= start_.samples())
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{
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start_ -= 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_.samples() - std::min<std::size_t>(current_, length_.samples())) / length_.samples();
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samples[i + 0] *= m;
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samples[i + 1] *= m;
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current_ += 2;
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}
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start_ = {};
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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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duration length_;
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duration start_;
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std::size_t current_ = 0;
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};
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}
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stream_ptr fade_out(stream_ptr stream, duration length, duration 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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