alc/effects/echo.cpp

   1 /**
   2  * OpenAL cross platform audio library
   3  * Copyright (C) 2009 by Chris Robinson.
   4  * This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU Library General Public
   6  *  License as published by the Free Software Foundation; either
   7  *  version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  *  Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  *  License along with this library; if not, write to the
  16  *  Free Software Foundation, Inc.,
  17  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  * Or go to http://www.gnu.org/copyleft/lgpl.html
  19  */
  20
  21 #include "config.h"
  22
  23 #include <algorithm>
  24 #include <array>
  25 #include <cstdlib>
  26 #include <iterator>
  27 #include <tuple>
  28
  29 #include "alc/effects/base.h"
  30 #include "almalloc.h"
  31 #include "alnumeric.h"
  32 #include "alspan.h"
  33 #include "core/bufferline.h"
  34 #include "core/context.h"
  35 #include "core/devformat.h"
  36 #include "core/device.h"
  37 #include "core/effectslot.h"
  38 #include "core/filters/biquad.h"
  39 #include "core/mixer.h"
  40 #include "intrusive_ptr.h"
  41 #include "opthelpers.h"
  42 #include "vector.h"
  43
  44
  45 namespace {
  46
  47 using uint = unsigned int;
  48
  49 constexpr float LowpassFreqRef{5000.0f};
  50
  51 struct EchoState final : public EffectState {
  52     al::vector<float,16> mSampleBuffer;
  53
  54     // The echo is two tap. The delay is the number of samples from before the
  55     // current offset
  56     struct {
  57         size_t delay{0u};
  58     } mTap[2];
  59     size_t mOffset{0u};
  60
  61     /* The panning gains for the two taps */
  62     struct {
  63         float Current[MAX_OUTPUT_CHANNELS]{};
  64         float Target[MAX_OUTPUT_CHANNELS]{};
  65     } mGains[2];
  66
  67     BiquadFilter mFilter;
  68     float mFeedGain{0.0f};
  69
  70     alignas(16) float mTempBuffer[2][BufferLineSize];
  71
  72     void deviceUpdate(const DeviceBase *device, const Buffer &buffer) override;
  73     void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
  74         const EffectTarget target) override;
  75     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
  76         const al::span<FloatBufferLine> samplesOut) override;
  77
  78     DEF_NEWDEL(EchoState)
  79 };
  80
  81 void EchoState::deviceUpdate(const DeviceBase *Device, const Buffer&)
  82 {
  83     const auto frequency = static_cast<float>(Device->Frequency);
  84
  85     // Use the next power of 2 for the buffer length, so the tap offsets can be
  86     // wrapped using a mask instead of a modulo
  87     const uint maxlen{NextPowerOf2(float2uint(EchoMaxDelay*frequency + 0.5f) +
  88         float2uint(EchoMaxLRDelay*frequency + 0.5f))};
  89     if(maxlen != mSampleBuffer.size())
  90         al::vector<float,16>(maxlen).swap(mSampleBuffer);
  91
  92     std::fill(mSampleBuffer.begin(), mSampleBuffer.end(), 0.0f);
  93     for(auto &e : mGains)
  94     {
  95         std::fill(std::begin(e.Current), std::end(e.Current), 0.0f);
  96         std::fill(std::begin(e.Target), std::end(e.Target), 0.0f);
  97     }
  98 }
  99
 100 void EchoState::update(const ContextBase *context, const EffectSlot *slot,
 101     const EffectProps *props, const EffectTarget target)
 102 {
 103     const DeviceBase *device{context->mDevice};
 104     const auto frequency = static_cast<float>(device->Frequency);
 105
 106     mTap[0].delay = maxu(float2uint(props->Echo.Delay*frequency + 0.5f), 1);
 107     mTap[1].delay = float2uint(props->Echo.LRDelay*frequency + 0.5f) + mTap[0].delay;
 108
 109     const float gainhf{maxf(1.0f - props->Echo.Damping, 0.0625f)}; /* Limit -24dB */
 110     mFilter.setParamsFromSlope(BiquadType::HighShelf, LowpassFreqRef/frequency, gainhf, 1.0f);
 111
 112     mFeedGain = props->Echo.Feedback;
 113
 114     /* Convert echo spread (where 0 = center, +/-1 = sides) to angle. */
 115     const float angle{std::asin(props->Echo.Spread)};
 116
 117     const auto coeffs0 = CalcAngleCoeffs(-angle, 0.0f, 0.0f);
 118     const auto coeffs1 = CalcAngleCoeffs( angle, 0.0f, 0.0f);
 119
 120     mOutTarget = target.Main->Buffer;
 121     ComputePanGains(target.Main, coeffs0.data(), slot->Gain, mGains[0].Target);
 122     ComputePanGains(target.Main, coeffs1.data(), slot->Gain, mGains[1].Target);
 123 }
 124
 125 void EchoState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 126 {
 127     const size_t mask{mSampleBuffer.size()-1};
 128     float *RESTRICT delaybuf{mSampleBuffer.data()};
 129     size_t offset{mOffset};
 130     size_t tap1{offset - mTap[0].delay};
 131     size_t tap2{offset - mTap[1].delay};
 132     float z1, z2;
 133
 134     ASSUME(samplesToDo > 0);
 135
 136     const BiquadFilter filter{mFilter};
 137     std::tie(z1, z2) = mFilter.getComponents();
 138     for(size_t i{0u};i < samplesToDo;)
 139     {
 140         offset &= mask;
 141         tap1 &= mask;
 142         tap2 &= mask;
 143
 144         size_t td{minz(mask+1 - maxz(offset, maxz(tap1, tap2)), samplesToDo-i)};
 145         do {
 146             /* Feed the delay buffer's input first. */
 147             delaybuf[offset] = samplesIn[0][i];
 148
 149             /* Get delayed output from the first and second taps. Use the
 150              * second tap for feedback.
 151              */
 152             mTempBuffer[0][i] = delaybuf[tap1++];
 153             mTempBuffer[1][i] = delaybuf[tap2++];
 154             const float feedb{mTempBuffer[1][i++]};
 155
 156             /* Add feedback to the delay buffer with damping and attenuation. */
 157             delaybuf[offset++] += filter.processOne(feedb, z1, z2) * mFeedGain;
 158         } while(--td);
 159     }
 160     mFilter.setComponents(z1, z2);
 161     mOffset = offset;
 162
 163     for(size_t c{0};c < 2;c++)
 164         MixSamples({mTempBuffer[c], samplesToDo}, samplesOut, mGains[c].Current, mGains[c].Target,
 165             samplesToDo, 0);
 166 }
 167
 168
 169 struct EchoStateFactory final : public EffectStateFactory {
 170     al::intrusive_ptr<EffectState> create() override
 171     { return al::intrusive_ptr<EffectState>{new EchoState{}}; }
 172 };
 173
 174 } // namespace
 175
 176 EffectStateFactory *EchoStateFactory_getFactory()
 177 {
 178     static EchoStateFactory EchoFactory{};
 179     return &EchoFactory;
 180 }