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Don't manually reverse samples

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This commit is contained in:
Chris Robinson 2022-03-31 13:07:58 -07:00
parent 7c60d0f163
commit 6f9311b1ba
3 changed files with 21 additions and 24 deletions
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30
core/bformatdec.cpp
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@ -133,31 +133,25 @@ void BFormatDec::processStablize(const al::span<FloatBufferLine> OutBuffer,
for(size_t i{0};i < SamplesToDo;++i)
side[FrontStablizer::DelayLength+i] += OutBuffer[lidx][i] - OutBuffer[ridx][i];
/* Combine the delayed mid signal with the decoded mid signal. Note that
* the samples are stored and combined in reverse, so the newest samples
* are at the front and the oldest at the back.
*/
al::span<float> tmpbuf{mStablizer->TempBuf.data(), SamplesToDo+FrontStablizer::DelayLength};
auto tmpiter = tmpbuf.begin() + SamplesToDo;
std::copy(mStablizer->MidDelay.cbegin(), mStablizer->MidDelay.cend(), tmpiter);
for(size_t i{0};i < SamplesToDo;++i)
*--tmpiter = OutBuffer[lidx][i] + OutBuffer[ridx][i];
/* Combine the delayed mid signal with the decoded mid signal. */
float *tmpbuf{mStablizer->TempBuf.data()};
auto tmpiter = std::copy(mStablizer->MidDelay.cbegin(), mStablizer->MidDelay.cend(), tmpbuf);
for(size_t i{0};i < SamplesToDo;++i,++tmpiter)
*tmpiter = OutBuffer[lidx][i] + OutBuffer[ridx][i];
/* Save the newest samples for next time. */
std::copy_n(tmpbuf.cbegin(), mStablizer->MidDelay.size(), mStablizer->MidDelay.begin());
std::copy_n(tmpbuf+SamplesToDo, mStablizer->MidDelay.size(), mStablizer->MidDelay.begin());
/* Apply an all-pass on the reversed signal, then reverse the samples to
* get the forward signal with a reversed phase shift. The future samples
* are included with the all-pass to reduce the error in the output
* samples (the smaller the delay, the more error is introduced).
/* Apply an all-pass on the signal in reverse. The future samples are
* included with the all-pass to reduce the error in the output samples
* (the smaller the delay, the more error is introduced).
*/
mStablizer->MidFilter.applyAllpass(tmpbuf);
tmpbuf = tmpbuf.subspan<FrontStablizer::DelayLength>();
std::reverse(tmpbuf.begin(), tmpbuf.end());
mStablizer->MidFilter.applyAllpassRev({tmpbuf, SamplesToDo+FrontStablizer::DelayLength});
/* Now apply the band-splitter, combining its phase shift with the reversed
* phase shift, restoring the original phase on the split signal.
*/
mStablizer->MidFilter.process(tmpbuf, mStablizer->MidHF.data(), mStablizer->MidLF.data());
mStablizer->MidFilter.process({tmpbuf, SamplesToDo}, mStablizer->MidHF.data(),
mStablizer->MidLF.data());
/* This pans the separate low- and high-frequency signals between being on
* the center channel and the left+right channels. The low-frequency signal

4
core/filters/splitter.cpp
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@ -160,7 +160,7 @@ void BandSplitterR<Real>::processScale(const al::span<Real> samples, const Real
}
template<typename Real>
void BandSplitterR<Real>::applyAllpass(const al::span<Real> samples) const
void BandSplitterR<Real>::applyAllpassRev(const al::span<Real> samples) const
{
const Real coeff{mCoeff};
Real z1{0.0f};
@ -170,7 +170,7 @@ void BandSplitterR<Real>::applyAllpass(const al::span<Real> samples) const
z1 = in - out*coeff;
return out;
};
std::transform(samples.begin(), samples.end(), samples.begin(), proc_sample);
std::transform(samples.rbegin(), samples.rend(), samples.rbegin(), proc_sample);
}

11
core/filters/splitter.h
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@ -29,11 +29,14 @@ public:
void processHfScale(const al::span<Real> samples, const Real hfscale);
void processScale(const al::span<Real> samples, const Real hfscale, const Real lfscale);
/* The all-pass portion of the band splitter. Applies the same phase shift
* without splitting the signal. Note that each use of this method is
* indepedent, it does not track history between calls.
/**
* The all-pass portion of the band splitter. Applies the same phase shift
* without splitting the signal, in reverse. It starts from the back of the
* span and works toward the front, creating a phase shift of -n degrees
* instead of +n. Note that each use of this method is indepedent, it does
* not track history between calls.
*/
void applyAllpass(const al::span<Real> samples) const;
void applyAllpassRev(const al::span<Real> samples) const;
};
using BandSplitter = BandSplitterR<float>;