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/**
* OpenAL cross platform audio library
* Copyright (C) 2013 by Anis A. Hireche
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
* Or go to http://www.gnu.org/copyleft/lgpl.html
*/
#include "config.h"
#include <cstdlib>
#include "alcmain.h"
#include "alcontext.h"
#include "alu.h"
#include "effectslot.h"
#include "vecmat.h"
namespace {
#define AMP_ENVELOPE_MIN 0.5f
#define AMP_ENVELOPE_MAX 2.0f
#define ATTACK_TIME 0.1f /* 100ms to rise from min to max */
#define RELEASE_TIME 0.2f /* 200ms to drop from max to min */
struct CompressorState final : public EffectState {
/* Effect gains for each channel */
float mGain[MaxAmbiChannels][MAX_OUTPUT_CHANNELS]{};
/* Effect parameters */
bool mEnabled{true};
float mAttackMult{1.0f};
float mReleaseMult{1.0f};
float mEnvFollower{1.0f};
void deviceUpdate(const ALCdevice *device, const Buffer &buffer) override;
void update(const ALCcontext *context, const EffectSlot *slot, const EffectProps *props,
const EffectTarget target) override;
void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
const al::span<FloatBufferLine> samplesOut) override;
DEF_NEWDEL(CompressorState)
};
void CompressorState::deviceUpdate(const ALCdevice *device, const Buffer&)
{
/* Number of samples to do a full attack and release (non-integer sample
* counts are okay).
*/
const float attackCount{static_cast<float>(device->Frequency) * ATTACK_TIME};
const float releaseCount{static_cast<float>(device->Frequency) * RELEASE_TIME};
/* Calculate per-sample multipliers to attack and release at the desired
* rates.
*/
mAttackMult = std::pow(AMP_ENVELOPE_MAX/AMP_ENVELOPE_MIN, 1.0f/attackCount);
mReleaseMult = std::pow(AMP_ENVELOPE_MIN/AMP_ENVELOPE_MAX, 1.0f/releaseCount);
}
void CompressorState::update(const ALCcontext*, const EffectSlot *slot,
const EffectProps *props, const EffectTarget target)
{
mEnabled = props->Compressor.OnOff;
mOutTarget = target.Main->Buffer;
auto set_gains = [slot,target](auto &gains, al::span<const float,MaxAmbiChannels> coeffs)
{ ComputePanGains(target.Main, coeffs.data(), slot->Gain, gains); };
SetAmbiPanIdentity(std::begin(mGain), slot->Wet.Buffer.size(), set_gains);
}
void CompressorState::process(const size_t samplesToDo,
const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
{
for(size_t base{0u};base < samplesToDo;)
{
float gains[256];
const size_t td{minz(256, samplesToDo-base)};
/* Generate the per-sample gains from the signal envelope. */
float env{mEnvFollower};
if(mEnabled)
{
for(size_t i{0u};i < td;++i)
{
/* Clamp the absolute amplitude to the defined envelope limits,
* then attack or release the envelope to reach it.
*/
const float amplitude{clampf(std::fabs(samplesIn[0][base+i]), AMP_ENVELOPE_MIN,
AMP_ENVELOPE_MAX)};
if(amplitude > env)
env = minf(env*mAttackMult, amplitude);
else if(amplitude < env)
env = maxf(env*mReleaseMult, amplitude);
/* Apply the reciprocal of the envelope to normalize the volume
* (compress the dynamic range).
*/
gains[i] = 1.0f / env;
}
}
else
{
/* Same as above, except the amplitude is forced to 1. This helps
* ensure smooth gain changes when the compressor is turned on and
* off.
*/
for(size_t i{0u};i < td;++i)
{
const float amplitude{1.0f};
if(amplitude > env)
env = minf(env*mAttackMult, amplitude);
else if(amplitude < env)
env = maxf(env*mReleaseMult, amplitude);
gains[i] = 1.0f / env;
}
}
mEnvFollower = env;
/* Now compress the signal amplitude to output. */
auto changains = std::addressof(mGain[0]);
for(const auto &input : samplesIn)
{
const float *outgains{*(changains++)};
for(FloatBufferLine &output : samplesOut)
{
const float gain{*(outgains++)};
if(!(std::fabs(gain) > GainSilenceThreshold))
continue;
for(size_t i{0u};i < td;i++)
output[base+i] += input[base+i] * gains[i] * gain;
}
}
base += td;
}
}
struct CompressorStateFactory final : public EffectStateFactory {
al::intrusive_ptr<EffectState> create() override
{ return al::intrusive_ptr<EffectState>{new CompressorState{}}; }
};
} // namespace
EffectStateFactory *CompressorStateFactory_getFactory()
{
static CompressorStateFactory CompressorFactory{};
return &CompressorFactory;
}
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