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.
67 lines
2.1 KiB
C++
67 lines
2.1 KiB
C++
/*
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* Copyright (c) 2026-present, the Ladybird developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/NonnullRefPtr.h>
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#include <AK/OwnPtr.h>
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#include <AK/RefPtr.h>
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#include <LibMedia/Audio/SampleSpecification.h>
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#include <LibMedia/Audio/TimeStretcher.h>
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#include <LibMedia/AudioBlock.h>
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#include <LibMedia/Export.h>
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#include <LibMedia/PipelineStatus.h>
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#include <LibMedia/Processors/AudioProcessor.h>
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#include <LibMedia/Producers/AudioProducer.h>
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#include <LibSync/Mutex.h>
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namespace Media {
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class MEDIA_API AudioTimeStretchProcessor final : public AudioProcessor {
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public:
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static ErrorOr<NonnullRefPtr<AudioTimeStretchProcessor>> try_create();
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AudioTimeStretchProcessor();
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virtual ~AudioTimeStretchProcessor() override;
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virtual ErrorOr<void> connect_input(NonnullRefPtr<AudioProducer> const&) override;
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virtual void disconnect_input(NonnullRefPtr<AudioProducer> const&) override;
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virtual void seek(AK::Duration) override;
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virtual ErrorOr<void> set_output_sample_specification(Audio::SampleSpecification) override;
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virtual void start() override;
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virtual PipelineStatus status() const override;
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virtual void pull(AudioBlock&) override;
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virtual void set_wake_handler(PipelineWakeHandler) override;
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virtual void set_playback_rate(float) override;
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private:
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void ensure_stretcher_while_locked() const;
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void maybe_recover_from_stale_upstream_eos_while_locked() const;
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PipelineStatus produce_block_while_locked(AudioBlock&) const;
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void dispatch_wake();
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mutable Sync::Mutex m_mutex;
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Audio::SampleSpecification m_sample_specification;
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RefPtr<AudioProducer> m_input;
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float m_playback_rate { 1.0f };
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mutable OwnPtr<Audio::TimeStretcher> m_stretcher;
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bool m_started { false };
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mutable i64 m_next_output_frame { 0 };
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mutable AK::Duration m_next_emit_media_time;
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mutable bool m_stretcher_reached_eos { false };
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mutable AudioBlock m_input_block;
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mutable AudioBlock m_pending_block;
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mutable bool m_downstream_needs_wake { true };
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bool m_moved_position_pending { false };
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PipelineWakeHandler m_wake_handler;
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};
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}
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