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60 lines
1.9 KiB
C++
60 lines
1.9 KiB
C++
/*
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* Copyright (c) 2023, kleines Filmröllchen <filmroellchen@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "QOATypes.h"
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#include <AK/Endian.h>
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#include <AK/Stream.h>
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namespace Audio::QOA {
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ErrorOr<FrameHeader> FrameHeader::read_from_stream(Stream& stream)
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{
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FrameHeader header;
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header.num_channels = TRY(stream.read_value<u8>());
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u8 sample_rate[3];
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// Enforce the order of the reads here, since the order of expression evaluations further down is implementation-defined.
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sample_rate[0] = TRY(stream.read_value<u8>());
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sample_rate[1] = TRY(stream.read_value<u8>());
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sample_rate[2] = TRY(stream.read_value<u8>());
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header.sample_rate = (sample_rate[0] << 16) | (sample_rate[1] << 8) | sample_rate[2];
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header.sample_count = TRY(stream.read_value<BigEndian<u16>>());
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header.frame_size = TRY(stream.read_value<BigEndian<u16>>());
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return header;
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}
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LMSState::LMSState(u64 history_packed, u64 weights_packed)
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{
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for (size_t i = 0; i < lms_history; ++i) {
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// The casts ensure proper sign extension.
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history[i] = static_cast<i16>(history_packed >> 48);
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history_packed <<= 16;
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weights[i] = static_cast<i16>(weights_packed >> 48);
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weights_packed <<= 16;
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}
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}
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i32 LMSState::predict() const
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{
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// The spec specifies that overflows are not allowed, but we do a safe thing anyways.
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Checked<i32> prediction = 0;
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for (size_t i = 0; i < lms_history; ++i)
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prediction.saturating_add(Checked<i32>::saturating_mul(history[i], weights[i]));
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return prediction.value() >> 13;
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}
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void LMSState::update(i32 sample, i32 residual)
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{
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i32 delta = residual >> 4;
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for (size_t i = 0; i < lms_history; ++i)
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weights[i] += history[i] < 0 ? -delta : delta;
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for (size_t i = 0; i < lms_history - 1; ++i)
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history[i] = history[i + 1];
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history[lms_history - 1] = sample;
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}
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}
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