71 lines
1.4 KiB
C++
71 lines
1.4 KiB
C++
#include <psemek/audio/effect/fade_in.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_in_impl
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: stream
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{
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fade_in_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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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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auto const count = stream_->read(samples);
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std::fill(samples.begin(), samples.begin() + std::min<std::size_t>(count, start_.samples()), 0.f);
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if (count <= start_.samples())
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{
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start_ -= count;
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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 < count; i += 2)
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{
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float m = static_cast<float>(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_ = duration{};
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}
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return count;
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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_in(stream_ptr stream, duration length, duration start)
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{
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return std::make_shared<fade_in_impl>(std::move(stream), length, start);
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}
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}
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