28f670f09f
The algorithm is ported over from Chromium's, which produces very good results for speech, while being not objectionable for music, especially in the background. Other algorithms were tested. Phase vocoders: - Bungee - Signalsmith Stretch - pvdoneright All three of these exhibited the usual phase shifting artifacts, causing speech to sound slightly shifted into the high end. Speech is the main thing we want to optimize for, so these aren't ideal. Sonic (TD-PSOLA) performs better than WSOLA for speech, especially at rates higher than 2x, but makes background sounds/music garbled and unpleasant. It is still worth considering for speech clarity, and could be added as an optional feature.
52 lines
1.5 KiB
C++
52 lines
1.5 KiB
C++
/*
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* Copyright 2013 The Chromium Authors
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* Copyright (c) 2026-present, the Ladybird developers.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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// Source: chromium/media/filters/wsola_internals.{h,cc}.
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#pragma once
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#include <AK/Span.h>
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#include <AK/Types.h>
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namespace Media {
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class AudioBlock;
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}
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namespace Audio::WSOLAInternals {
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struct Interval {
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size_t low;
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size_t high;
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};
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void multi_channel_dot_product(Media::AudioBlock const& a, size_t frame_offset_a,
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Media::AudioBlock const& b, size_t frame_offset_b,
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size_t num_frames, Span<float> dot_product);
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void multi_channel_moving_block_energies(Media::AudioBlock const& input,
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size_t frames_per_window, Span<float> energy);
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void quadratic_interpolation(ReadonlySpan<float> y_values,
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float& extremum, float& extremum_value);
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size_t decimated_search(size_t decimation, Interval exclude_interval,
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Media::AudioBlock const& target_block, Media::AudioBlock const& search_segment,
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ReadonlySpan<float> energy_target_block,
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ReadonlySpan<float> energy_candidate_blocks);
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size_t full_search(size_t low_limit, size_t high_limit, Interval exclude_interval,
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Media::AudioBlock const& target_block, Media::AudioBlock const& search_block,
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ReadonlySpan<float> energy_target_block,
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ReadonlySpan<float> energy_candidate_blocks);
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size_t optimal_index(Media::AudioBlock const& search_block, Media::AudioBlock const& target_block,
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Interval exclude_interval);
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void get_periodic_hanning_window(Span<float> window);
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}
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