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LibAudio: Resample with integer ratios instead of floats
Floating-point ratios are inherently imprecise, and can lead to unpredictable or nondeterministic behavior when resampling and expecting a certain number of resulting samples. Therefore, the resampler now uses integer ratios, with almost identical but fully predictable behavior. This also introduces the reset() function that the FLAC loader will use in the future.
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2 changed files with 27 additions and 11 deletions
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@ -8,6 +8,7 @@
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#include "Buffer.h"
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#include <AK/Atomic.h>
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#include <AK/Debug.h>
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#include <AK/StdLibExtras.h>
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#include <AK/String.h>
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namespace Audio {
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@ -167,18 +168,19 @@ RefPtr<Buffer> Buffer::from_pcm_stream(InputMemoryStream& stream, ResampleHelper
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}
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template<typename SampleType>
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ResampleHelper<SampleType>::ResampleHelper(double source, double target)
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: m_ratio(source / target)
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ResampleHelper<SampleType>::ResampleHelper(u32 source, u32 target)
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: m_source(source)
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, m_target(target)
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{
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}
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template ResampleHelper<i32>::ResampleHelper(double, double);
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template ResampleHelper<double>::ResampleHelper(double, double);
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template ResampleHelper<i32>::ResampleHelper(u32, u32);
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template ResampleHelper<double>::ResampleHelper(u32, u32);
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template<typename SampleType>
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Vector<SampleType> ResampleHelper<SampleType>::resample(Vector<SampleType> to_resample)
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{
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Vector<SampleType> resampled;
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resampled.ensure_capacity(to_resample.size() * m_ratio);
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resampled.ensure_capacity(to_resample.size() * ceil_div(m_source, m_target));
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for (auto sample : to_resample) {
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process_sample(sample, sample);
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@ -196,7 +198,7 @@ void ResampleHelper<SampleType>::process_sample(SampleType sample_l, SampleType
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{
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m_last_sample_l = sample_l;
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m_last_sample_r = sample_r;
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m_current_ratio += 1;
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m_current_ratio += m_target;
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}
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template void ResampleHelper<i32>::process_sample(i32, i32);
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template void ResampleHelper<double>::process_sample(double, double);
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@ -204,8 +206,8 @@ template void ResampleHelper<double>::process_sample(double, double);
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template<typename SampleType>
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bool ResampleHelper<SampleType>::read_sample(SampleType& next_l, SampleType& next_r)
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{
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if (m_current_ratio > 0) {
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m_current_ratio -= m_ratio;
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if (m_current_ratio >= m_source) {
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m_current_ratio -= m_source;
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next_l = m_last_sample_l;
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next_r = m_last_sample_r;
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return true;
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@ -216,4 +218,15 @@ bool ResampleHelper<SampleType>::read_sample(SampleType& next_l, SampleType& nex
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template bool ResampleHelper<i32>::read_sample(i32&, i32&);
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template bool ResampleHelper<double>::read_sample(double&, double&);
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template<typename SampleType>
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void ResampleHelper<SampleType>::reset()
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{
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m_current_ratio = 0;
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m_last_sample_l = {};
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m_last_sample_r = {};
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}
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template void ResampleHelper<i32>::reset();
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template void ResampleHelper<double>::reset();
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}
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