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Commit da153363 authored by Antti S. Lankila's avatar Antti S. Lankila
Browse files

Take some ideas from bs2b. 

Bs2b uses the low-pass filter to generate the delay as a byproduct
of its operation. The filter is generally set around 700 Hz where
it produces about 250 microseconds of delay. In addition to that,
the crossfeed is now mixed at -6 dB level. The reverb is unchanged,
although the new configuration gives it larger role in forming
an impression of a soundstage.

The design is still not complete, but good enough for a commit.
parent 89e1cbe5

libs/audioflinger/AudioDSP.cpp

+4 −31
Original line number Diff line number Diff line
@@ -33,7 +33,6 @@ static int16_t toFixedPoint(float x) 
    return int16_t(x * (1 << fixedPointDecimals) + 0.5f);

}





/***************************************************************************

 * Delay                                                                   *

 ***************************************************************************/
@@ -403,12 +402,6 @@ EffectHeadphone::~EffectHeadphone() 
{

    delete &mReverbDelayL;

    delete &mReverbDelayR;

    delete &mDelayL;

    delete &mDelayR;

    for (int32_t i = 0; i < 3; i ++) {

        delete &mAllpassL[i];

        delete &mAllpassR[i];

    }

    delete &mLowpassL;

    delete &mLowpassR;

}
@@ -418,16 +411,8 @@ void EffectHeadphone::configure(const float samplingFrequency) { 


    mReverbDelayL.setParameters(mSamplingFrequency, 0.030f);

    mReverbDelayR.setParameters(mSamplingFrequency, 0.030f);

    mDelayL.setParameters(mSamplingFrequency, 0.00045f);

    mDelayR.setParameters(mSamplingFrequency, 0.00045f);

    mAllpassL[0].setParameters(mSamplingFrequency, 0.4f, 0.00031f);

    mAllpassR[0].setParameters(mSamplingFrequency, 0.4f, 0.00031f);

    mAllpassL[1].setParameters(mSamplingFrequency, 0.4f, 0.00021f);

    mAllpassR[1].setParameters(mSamplingFrequency, 0.4f, 0.00021f);

    mAllpassL[2].setParameters(mSamplingFrequency, 0.4f, 0.00011f);

    mAllpassR[2].setParameters(mSamplingFrequency, 0.4f, 0.00011f);

    mLowpassL.setRC(4000.0f, mSamplingFrequency);

    mLowpassR.setRC(4000.0f, mSamplingFrequency);

    mLowpassL.setRC(700.0f, mSamplingFrequency);

    mLowpassR.setRC(700.0f, mSamplingFrequency);

}



void EffectHeadphone::setDeep(bool deep)
@@ -479,26 +464,14 @@ void EffectHeadphone::process(int32_t* inout, int32_t frames) 
        dataL += dryL;

        dataR += dryR;



        /* Add fixed ear-to-ear propagation delay of about 10 cm, based

         * on the idea that ear-to-ear distance is 30 cm and the speakers

         * are placed in front of the listener, which means that the actual

         * time delay will be somewhat less than the maximum. */

        dataL = mDelayL.process(dataL);

        dataR = mDelayR.process(dataR);

        for (int32_t j = 0; j < 3; j ++) {

            /* Confuse phase, simulating shoulder echoes and whatnot. */

            dataL = mAllpassL[j].process(dataL);

            dataR = mAllpassR[j].process(dataR);

        }



        /* Lowpass filter to estimate head shadow. */

        dataL = mLowpassL.process(dataL >> fixedPointDecimals);

        dataR = mLowpassR.process(dataR >> fixedPointDecimals);

        /* 28 bits */

        

        /* Mix right-to-left and vice versa. */

        inout[0] += dataR;

        inout[1] += dataL;

        inout[0] += dataR >> 1;

        inout[1] += dataL >> 1;

        inout += 2;

    }

}

libs/audioflinger/AudioDSP.h

+0 −2
Original line number Diff line number Diff line
@@ -119,8 +119,6 @@ class EffectHeadphone : public Effect { 


    Delay mReverbDelayL, mReverbDelayR;

    int32_t mDelayDataL, mDelayDataR;

    Delay mDelayL, mDelayR;

    Allpass mAllpassL[3], mAllpassR[3];

    Biquad mLowpassL, mLowpassR;



    public: