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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #define LOG_TAG "AudioResamplerSinc"
     18 //#define LOG_NDEBUG 0
     19 
     20 #define __STDC_CONSTANT_MACROS
     21 #include <malloc.h>
     22 #include <string.h>
     23 #include <stdlib.h>
     24 #include <dlfcn.h>
     25 
     26 #include <cutils/compiler.h>
     27 #include <cutils/properties.h>
     28 
     29 #include <utils/Log.h>
     30 #include <audio_utils/primitives.h>
     31 
     32 #include "AudioResamplerSinc.h"
     33 
     34 #if defined(__clang__) && !__has_builtin(__builtin_assume_aligned)
     35 #define __builtin_assume_aligned(p, a) \
     36 	(((uintptr_t(p) % (a)) == 0) ? (p) : (__builtin_unreachable(), (p)))
     37 #endif
     38 
     39 #if defined(__arm__) && !defined(__thumb__)
     40 #define USE_INLINE_ASSEMBLY (true)
     41 #else
     42 #define USE_INLINE_ASSEMBLY (false)
     43 #endif
     44 
     45 #if defined(__aarch64__) || defined(__ARM_NEON__)
     46 #ifndef USE_NEON
     47 #define USE_NEON (true)
     48 #endif
     49 #else
     50 #define USE_NEON (false)
     51 #endif
     52 #if USE_NEON
     53 #include <arm_neon.h>
     54 #endif
     55 
     56 #define UNUSED(x) ((void)(x))
     57 
     58 namespace android {
     59 // ----------------------------------------------------------------------------
     60 
     61 
     62 /*
     63  * These coeficients are computed with the "fir" utility found in
     64  * tools/resampler_tools
     65  * cmd-line: fir -l 7 -s 48000 -c 20478
     66  */
     67 const uint32_t AudioResamplerSinc::mFirCoefsUp[] __attribute__ ((aligned (32))) = {
     68 #include "AudioResamplerSincUp.h"
     69 };
     70 
     71 /*
     72  * These coefficients are optimized for 48KHz -> 44.1KHz
     73  * cmd-line: fir -l 7 -s 48000 -c 17189
     74  */
     75 const uint32_t AudioResamplerSinc::mFirCoefsDown[] __attribute__ ((aligned (32))) = {
     76 #include "AudioResamplerSincDown.h"
     77 };
     78 
     79 // we use 15 bits to interpolate between these samples
     80 // this cannot change because the mul below rely on it.
     81 static const int pLerpBits = 15;
     82 
     83 static pthread_once_t once_control = PTHREAD_ONCE_INIT;
     84 static readCoefficientsFn readResampleCoefficients = NULL;
     85 
     86 /*static*/ AudioResamplerSinc::Constants AudioResamplerSinc::highQualityConstants;
     87 /*static*/ AudioResamplerSinc::Constants AudioResamplerSinc::veryHighQualityConstants;
     88 
     89 void AudioResamplerSinc::init_routine()
     90 {
     91     // for high quality resampler, the parameters for coefficients are compile-time constants
     92     Constants *c = &highQualityConstants;
     93     c->coefsBits = RESAMPLE_FIR_LERP_INT_BITS;
     94     c->cShift = kNumPhaseBits - c->coefsBits;
     95     c->cMask = ((1<< c->coefsBits)-1) << c->cShift;
     96     c->pShift = kNumPhaseBits - c->coefsBits - pLerpBits;
     97     c->pMask = ((1<< pLerpBits)-1) << c->pShift;
     98     c->halfNumCoefs = RESAMPLE_FIR_NUM_COEF;
     99 
    100     // for very high quality resampler, the parameters are load-time constants
    101     veryHighQualityConstants = highQualityConstants;
    102 
    103     // Open the dll to get the coefficients for VERY_HIGH_QUALITY
    104     void *resampleCoeffLib = dlopen("libaudio-resampler.so", RTLD_NOW);
    105     ALOGV("Open libaudio-resampler library = %p", resampleCoeffLib);
    106     if (resampleCoeffLib == NULL) {
    107         ALOGE("Could not open audio-resampler library: %s", dlerror());
    108         return;
    109     }
    110 
    111     readResampleFirNumCoeffFn readResampleFirNumCoeff;
    112     readResampleFirLerpIntBitsFn readResampleFirLerpIntBits;
    113 
    114     readResampleCoefficients = (readCoefficientsFn)
    115             dlsym(resampleCoeffLib, "readResamplerCoefficients");
    116     readResampleFirNumCoeff = (readResampleFirNumCoeffFn)
    117             dlsym(resampleCoeffLib, "readResampleFirNumCoeff");
    118     readResampleFirLerpIntBits = (readResampleFirLerpIntBitsFn)
    119             dlsym(resampleCoeffLib, "readResampleFirLerpIntBits");
    120 
    121     if (!readResampleCoefficients || !readResampleFirNumCoeff || !readResampleFirLerpIntBits) {
    122         readResampleCoefficients = NULL;
    123         dlclose(resampleCoeffLib);
    124         resampleCoeffLib = NULL;
    125         ALOGE("Could not find symbol: %s", dlerror());
    126         return;
    127     }
    128 
    129     c = &veryHighQualityConstants;
    130     c->coefsBits = readResampleFirLerpIntBits();
    131     c->cShift = kNumPhaseBits - c->coefsBits;
    132     c->cMask = ((1<<c->coefsBits)-1) << c->cShift;
    133     c->pShift = kNumPhaseBits - c->coefsBits - pLerpBits;
    134     c->pMask = ((1<<pLerpBits)-1) << c->pShift;
    135     // number of zero-crossing on each side
    136     c->halfNumCoefs = readResampleFirNumCoeff();
    137     ALOGV("coefsBits = %d", c->coefsBits);
    138     ALOGV("halfNumCoefs = %d", c->halfNumCoefs);
    139     // note that we "leak" resampleCoeffLib until the process exits
    140 }
    141 
    142 // ----------------------------------------------------------------------------
    143 
    144 #if !USE_NEON
    145 
    146 static inline
    147 int32_t mulRL(int left, int32_t in, uint32_t vRL)
    148 {
    149 #if USE_INLINE_ASSEMBLY
    150     int32_t out;
    151     if (left) {
    152         asm( "smultb %[out], %[in], %[vRL] \n"
    153              : [out]"=r"(out)
    154              : [in]"%r"(in), [vRL]"r"(vRL)
    155              : );
    156     } else {
    157         asm( "smultt %[out], %[in], %[vRL] \n"
    158              : [out]"=r"(out)
    159              : [in]"%r"(in), [vRL]"r"(vRL)
    160              : );
    161     }
    162     return out;
    163 #else
    164     int16_t v = left ? int16_t(vRL) : int16_t(vRL>>16);
    165     return int32_t((int64_t(in) * v) >> 16);
    166 #endif
    167 }
    168 
    169 static inline
    170 int32_t mulAdd(int16_t in, int32_t v, int32_t a)
    171 {
    172 #if USE_INLINE_ASSEMBLY
    173     int32_t out;
    174     asm( "smlawb %[out], %[v], %[in], %[a] \n"
    175          : [out]"=r"(out)
    176          : [in]"%r"(in), [v]"r"(v), [a]"r"(a)
    177          : );
    178     return out;
    179 #else
    180     return a + int32_t((int64_t(v) * in) >> 16);
    181 #endif
    182 }
    183 
    184 static inline
    185 int32_t mulAddRL(int left, uint32_t inRL, int32_t v, int32_t a)
    186 {
    187 #if USE_INLINE_ASSEMBLY
    188     int32_t out;
    189     if (left) {
    190         asm( "smlawb %[out], %[v], %[inRL], %[a] \n"
    191              : [out]"=r"(out)
    192              : [inRL]"%r"(inRL), [v]"r"(v), [a]"r"(a)
    193              : );
    194     } else {
    195         asm( "smlawt %[out], %[v], %[inRL], %[a] \n"
    196              : [out]"=r"(out)
    197              : [inRL]"%r"(inRL), [v]"r"(v), [a]"r"(a)
    198              : );
    199     }
    200     return out;
    201 #else
    202     int16_t s = left ? int16_t(inRL) : int16_t(inRL>>16);
    203     return a + int32_t((int64_t(v) * s) >> 16);
    204 #endif
    205 }
    206 
    207 #endif // !USE_NEON
    208 
    209 // ----------------------------------------------------------------------------
    210 
    211 AudioResamplerSinc::AudioResamplerSinc(
    212         int inChannelCount, int32_t sampleRate, src_quality quality)
    213     : AudioResampler(inChannelCount, sampleRate, quality),
    214     mState(0), mImpulse(0), mRingFull(0), mFirCoefs(0)
    215 {
    216     /*
    217      * Layout of the state buffer for 32 tap:
    218      *
    219      * "present" sample            beginning of 2nd buffer
    220      *                 v                v
    221      *  0              01               2              23              3
    222      *  0              F0               0              F0              F
    223      * [pppppppppppppppInnnnnnnnnnnnnnnnpppppppppppppppInnnnnnnnnnnnnnnn]
    224      *                 ^               ^ head
    225      *
    226      * p = past samples, convoluted with the (p)ositive side of sinc()
    227      * n = future samples, convoluted with the (n)egative side of sinc()
    228      * r = extra space for implementing the ring buffer
    229      *
    230      */
    231 
    232     mVolumeSIMD[0] = 0;
    233     mVolumeSIMD[1] = 0;
    234 
    235     // Load the constants for coefficients
    236     int ok = pthread_once(&once_control, init_routine);
    237     if (ok != 0) {
    238         ALOGE("%s pthread_once failed: %d", __func__, ok);
    239     }
    240     mConstants = (quality == VERY_HIGH_QUALITY) ?
    241             &veryHighQualityConstants : &highQualityConstants;
    242 }
    243 
    244 
    245 AudioResamplerSinc::~AudioResamplerSinc() {
    246     free(mState);
    247 }
    248 
    249 void AudioResamplerSinc::init() {
    250     const Constants& c(*mConstants);
    251     const size_t numCoefs = 2 * c.halfNumCoefs;
    252     const size_t stateSize = numCoefs * mChannelCount * 2;
    253     mState = (int16_t*)memalign(32, stateSize*sizeof(int16_t));
    254     memset(mState, 0, sizeof(int16_t)*stateSize);
    255     mImpulse  = mState   + (c.halfNumCoefs-1)*mChannelCount;
    256     mRingFull = mImpulse + (numCoefs+1)*mChannelCount;
    257 }
    258 
    259 void AudioResamplerSinc::setVolume(float left, float right) {
    260     AudioResampler::setVolume(left, right);
    261     // convert to U4_28 (rounding down).
    262     // integer volume values are clamped to 0 to UNITY_GAIN.
    263     mVolumeSIMD[0] = u4_28_from_float(clampFloatVol(left));
    264     mVolumeSIMD[1] = u4_28_from_float(clampFloatVol(right));
    265 }
    266 
    267 size_t AudioResamplerSinc::resample(int32_t* out, size_t outFrameCount,
    268             AudioBufferProvider* provider)
    269 {
    270     // FIXME store current state (up or down sample) and only load the coefs when the state
    271     // changes. Or load two pointers one for up and one for down in the init function.
    272     // Not critical now since the read functions are fast, but would be important if read was slow.
    273     if (mConstants == &veryHighQualityConstants && readResampleCoefficients) {
    274         mFirCoefs = readResampleCoefficients( mInSampleRate <= mSampleRate );
    275     } else {
    276         mFirCoefs = (const int32_t *)
    277                 ((mInSampleRate <= mSampleRate) ? mFirCoefsUp : mFirCoefsDown);
    278     }
    279 
    280     // select the appropriate resampler
    281     switch (mChannelCount) {
    282     case 1:
    283         return resample<1>(out, outFrameCount, provider);
    284     case 2:
    285         return resample<2>(out, outFrameCount, provider);
    286     default:
    287         LOG_ALWAYS_FATAL("invalid channel count: %d", mChannelCount);
    288         return 0;
    289     }
    290 }
    291 
    292 
    293 template<int CHANNELS>
    294 size_t AudioResamplerSinc::resample(int32_t* out, size_t outFrameCount,
    295         AudioBufferProvider* provider)
    296 {
    297     const Constants& c(*mConstants);
    298     const size_t headOffset = c.halfNumCoefs*CHANNELS;
    299     int16_t* impulse = mImpulse;
    300     uint32_t vRL = mVolumeRL;
    301     size_t inputIndex = mInputIndex;
    302     uint32_t phaseFraction = mPhaseFraction;
    303     uint32_t phaseIncrement = mPhaseIncrement;
    304     size_t outputIndex = 0;
    305     size_t outputSampleCount = outFrameCount * 2;
    306     size_t inFrameCount = getInFrameCountRequired(outFrameCount);
    307 
    308     while (outputIndex < outputSampleCount) {
    309         // buffer is empty, fetch a new one
    310         while (mBuffer.frameCount == 0) {
    311             mBuffer.frameCount = inFrameCount;
    312             provider->getNextBuffer(&mBuffer);
    313             if (mBuffer.raw == NULL) {
    314                 goto resample_exit;
    315             }
    316             const uint32_t phaseIndex = phaseFraction >> kNumPhaseBits;
    317             if (phaseIndex == 1) {
    318                 // read one frame
    319                 read<CHANNELS>(impulse, phaseFraction, mBuffer.i16, inputIndex);
    320             } else if (phaseIndex == 2) {
    321                 // read 2 frames
    322                 read<CHANNELS>(impulse, phaseFraction, mBuffer.i16, inputIndex);
    323                 inputIndex++;
    324                 if (inputIndex >= mBuffer.frameCount) {
    325                     inputIndex -= mBuffer.frameCount;
    326                     provider->releaseBuffer(&mBuffer);
    327                 } else {
    328                     read<CHANNELS>(impulse, phaseFraction, mBuffer.i16, inputIndex);
    329                 }
    330             }
    331         }
    332         int16_t const * const in = mBuffer.i16;
    333         const size_t frameCount = mBuffer.frameCount;
    334 
    335         // Always read-in the first samples from the input buffer
    336         int16_t* head = impulse + headOffset;
    337         for (size_t i=0 ; i<CHANNELS ; i++) {
    338             head[i] = in[inputIndex*CHANNELS + i];
    339         }
    340 
    341         // handle boundary case
    342         while (CC_LIKELY(outputIndex < outputSampleCount)) {
    343             filterCoefficient<CHANNELS>(&out[outputIndex], phaseFraction, impulse, vRL);
    344             outputIndex += 2;
    345 
    346             phaseFraction += phaseIncrement;
    347             const size_t phaseIndex = phaseFraction >> kNumPhaseBits;
    348             for (size_t i=0 ; i<phaseIndex ; i++) {
    349                 inputIndex++;
    350                 if (inputIndex >= frameCount) {
    351                     goto done;  // need a new buffer
    352                 }
    353                 read<CHANNELS>(impulse, phaseFraction, in, inputIndex);
    354             }
    355         }
    356 done:
    357         // if done with buffer, save samples
    358         if (inputIndex >= frameCount) {
    359             inputIndex -= frameCount;
    360             provider->releaseBuffer(&mBuffer);
    361         }
    362     }
    363 
    364 resample_exit:
    365     mImpulse = impulse;
    366     mInputIndex = inputIndex;
    367     mPhaseFraction = phaseFraction;
    368     return outputIndex / CHANNELS;
    369 }
    370 
    371 template<int CHANNELS>
    372 /***
    373 * read()
    374 *
    375 * This function reads only one frame from input buffer and writes it in
    376 * state buffer
    377 *
    378 **/
    379 void AudioResamplerSinc::read(
    380         int16_t*& impulse, uint32_t& phaseFraction,
    381         const int16_t* in, size_t inputIndex)
    382 {
    383     impulse += CHANNELS;
    384     phaseFraction -= 1LU<<kNumPhaseBits;
    385 
    386     const Constants& c(*mConstants);
    387     if (CC_UNLIKELY(impulse >= mRingFull)) {
    388         const size_t stateSize = (c.halfNumCoefs*2)*CHANNELS;
    389         memcpy(mState, mState+stateSize, sizeof(int16_t)*stateSize);
    390         impulse -= stateSize;
    391     }
    392 
    393     int16_t* head = impulse + c.halfNumCoefs*CHANNELS;
    394     for (size_t i=0 ; i<CHANNELS ; i++) {
    395         head[i] = in[inputIndex*CHANNELS + i];
    396     }
    397 }
    398 
    399 template<int CHANNELS>
    400 void AudioResamplerSinc::filterCoefficient(int32_t* out, uint32_t phase,
    401          const int16_t *samples, uint32_t vRL)
    402 {
    403     // NOTE: be very careful when modifying the code here. register
    404     // pressure is very high and a small change might cause the compiler
    405     // to generate far less efficient code.
    406     // Always sanity check the result with objdump or test-resample.
    407 
    408     // compute the index of the coefficient on the positive side and
    409     // negative side
    410     const Constants& c(*mConstants);
    411     const int32_t ONE = c.cMask | c.pMask;
    412     uint32_t indexP = ( phase & c.cMask) >> c.cShift;
    413     uint32_t lerpP  = ( phase & c.pMask) >> c.pShift;
    414     uint32_t indexN = ((ONE-phase) & c.cMask) >> c.cShift;
    415     uint32_t lerpN  = ((ONE-phase) & c.pMask) >> c.pShift;
    416 
    417     const size_t offset = c.halfNumCoefs;
    418     indexP *= offset;
    419     indexN *= offset;
    420 
    421     int32_t const* coefsP = mFirCoefs + indexP;
    422     int32_t const* coefsN = mFirCoefs + indexN;
    423     int16_t const* sP = samples;
    424     int16_t const* sN = samples + CHANNELS;
    425 
    426     size_t count = offset;
    427 
    428 #if !USE_NEON
    429     int32_t l = 0;
    430     int32_t r = 0;
    431     for (size_t i=0 ; i<count ; i++) {
    432         interpolate<CHANNELS>(l, r, coefsP++, offset, lerpP, sP);
    433         sP -= CHANNELS;
    434         interpolate<CHANNELS>(l, r, coefsN++, offset, lerpN, sN);
    435         sN += CHANNELS;
    436     }
    437     out[0] += 2 * mulRL(1, l, vRL);
    438     out[1] += 2 * mulRL(0, r, vRL);
    439 #else
    440     UNUSED(vRL);
    441     if (CHANNELS == 1) {
    442         int32_t const* coefsP1 = coefsP + offset;
    443         int32_t const* coefsN1 = coefsN + offset;
    444         sP -= CHANNELS*3;
    445 
    446         int32x4_t sum;
    447         int32x2_t lerpPN;
    448         lerpPN = vdup_n_s32(0);
    449         lerpPN = vld1_lane_s32((int32_t *)&lerpP, lerpPN, 0);
    450         lerpPN = vld1_lane_s32((int32_t *)&lerpN, lerpPN, 1);
    451         lerpPN = vshl_n_s32(lerpPN, 16);
    452         sum = vdupq_n_s32(0);
    453 
    454         int16x4_t sampleP, sampleN;
    455         int32x4_t samplePExt, sampleNExt;
    456         int32x4_t coefsPV0, coefsPV1, coefsNV0, coefsNV1;
    457 
    458         coefsP = (const int32_t*)__builtin_assume_aligned(coefsP, 16);
    459         coefsN = (const int32_t*)__builtin_assume_aligned(coefsN, 16);
    460         coefsP1 = (const int32_t*)__builtin_assume_aligned(coefsP1, 16);
    461         coefsN1 = (const int32_t*)__builtin_assume_aligned(coefsN1, 16);
    462         for (; count > 0; count -= 4) {
    463             sampleP = vld1_s16(sP);
    464             sampleN = vld1_s16(sN);
    465             coefsPV0 = vld1q_s32(coefsP);
    466             coefsNV0 = vld1q_s32(coefsN);
    467             coefsPV1 = vld1q_s32(coefsP1);
    468             coefsNV1 = vld1q_s32(coefsN1);
    469             sP -= 4;
    470             sN += 4;
    471             coefsP += 4;
    472             coefsN += 4;
    473             coefsP1 += 4;
    474             coefsN1 += 4;
    475 
    476             sampleP = vrev64_s16(sampleP);
    477 
    478             // interpolate (step1)
    479             coefsPV1 = vsubq_s32(coefsPV1, coefsPV0);
    480             coefsNV1 = vsubq_s32(coefsNV1, coefsNV0);
    481             samplePExt = vshll_n_s16(sampleP, 15);
    482             // interpolate (step2)
    483             coefsPV1 = vqrdmulhq_lane_s32(coefsPV1, lerpPN, 0);
    484             coefsNV1 = vqrdmulhq_lane_s32(coefsNV1, lerpPN, 1);
    485             sampleNExt = vshll_n_s16(sampleN, 15);
    486             // interpolate (step3)
    487             coefsPV0 = vaddq_s32(coefsPV0, coefsPV1);
    488             coefsNV0 = vaddq_s32(coefsNV0, coefsNV1);
    489 
    490             samplePExt = vqrdmulhq_s32(samplePExt, coefsPV0);
    491             sampleNExt = vqrdmulhq_s32(sampleNExt, coefsNV0);
    492             sum = vaddq_s32(sum, samplePExt);
    493             sum = vaddq_s32(sum, sampleNExt);
    494         }
    495         int32x2_t volumesV, outV;
    496         volumesV = vld1_s32(mVolumeSIMD);
    497         outV = vld1_s32(out);
    498 
    499         //add all 4 partial sums
    500         int32x2_t sumLow, sumHigh;
    501         sumLow = vget_low_s32(sum);
    502         sumHigh = vget_high_s32(sum);
    503         sumLow = vpadd_s32(sumLow, sumHigh);
    504         sumLow = vpadd_s32(sumLow, sumLow);
    505 
    506         sumLow = vqrdmulh_s32(sumLow, volumesV);
    507         outV = vadd_s32(outV, sumLow);
    508         vst1_s32(out, outV);
    509     } else if (CHANNELS == 2) {
    510         int32_t const* coefsP1 = coefsP + offset;
    511         int32_t const* coefsN1 = coefsN + offset;
    512         sP -= CHANNELS*3;
    513 
    514         int32x4_t sum0, sum1;
    515         int32x2_t lerpPN;
    516 
    517         lerpPN = vdup_n_s32(0);
    518         lerpPN = vld1_lane_s32((int32_t *)&lerpP, lerpPN, 0);
    519         lerpPN = vld1_lane_s32((int32_t *)&lerpN, lerpPN, 1);
    520         lerpPN = vshl_n_s32(lerpPN, 16);
    521         sum0 = vdupq_n_s32(0);
    522         sum1 = vdupq_n_s32(0);
    523 
    524         int16x4x2_t sampleP, sampleN;
    525         int32x4x2_t samplePExt, sampleNExt;
    526         int32x4_t coefsPV0, coefsPV1, coefsNV0, coefsNV1;
    527 
    528         coefsP = (const int32_t*)__builtin_assume_aligned(coefsP, 16);
    529         coefsN = (const int32_t*)__builtin_assume_aligned(coefsN, 16);
    530         coefsP1 = (const int32_t*)__builtin_assume_aligned(coefsP1, 16);
    531         coefsN1 = (const int32_t*)__builtin_assume_aligned(coefsN1, 16);
    532         for (; count > 0; count -= 4) {
    533             sampleP = vld2_s16(sP);
    534             sampleN = vld2_s16(sN);
    535             coefsPV0 = vld1q_s32(coefsP);
    536             coefsNV0 = vld1q_s32(coefsN);
    537             coefsPV1 = vld1q_s32(coefsP1);
    538             coefsNV1 = vld1q_s32(coefsN1);
    539             sP -= 8;
    540             sN += 8;
    541             coefsP += 4;
    542             coefsN += 4;
    543             coefsP1 += 4;
    544             coefsN1 += 4;
    545 
    546             sampleP.val[0] = vrev64_s16(sampleP.val[0]);
    547             sampleP.val[1] = vrev64_s16(sampleP.val[1]);
    548 
    549             // interpolate (step1)
    550             coefsPV1 = vsubq_s32(coefsPV1, coefsPV0);
    551             coefsNV1 = vsubq_s32(coefsNV1, coefsNV0);
    552             samplePExt.val[0] = vshll_n_s16(sampleP.val[0], 15);
    553             samplePExt.val[1] = vshll_n_s16(sampleP.val[1], 15);
    554             // interpolate (step2)
    555             coefsPV1 = vqrdmulhq_lane_s32(coefsPV1, lerpPN, 0);
    556             coefsNV1 = vqrdmulhq_lane_s32(coefsNV1, lerpPN, 1);
    557             sampleNExt.val[0] = vshll_n_s16(sampleN.val[0], 15);
    558             sampleNExt.val[1] = vshll_n_s16(sampleN.val[1], 15);
    559             // interpolate (step3)
    560             coefsPV0 = vaddq_s32(coefsPV0, coefsPV1);
    561             coefsNV0 = vaddq_s32(coefsNV0, coefsNV1);
    562 
    563             samplePExt.val[0] = vqrdmulhq_s32(samplePExt.val[0], coefsPV0);
    564             samplePExt.val[1] = vqrdmulhq_s32(samplePExt.val[1], coefsPV0);
    565             sampleNExt.val[0] = vqrdmulhq_s32(sampleNExt.val[0], coefsNV0);
    566             sampleNExt.val[1] = vqrdmulhq_s32(sampleNExt.val[1], coefsNV0);
    567             sum0 = vaddq_s32(sum0, samplePExt.val[0]);
    568             sum1 = vaddq_s32(sum1, samplePExt.val[1]);
    569             sum0 = vaddq_s32(sum0, sampleNExt.val[0]);
    570             sum1 = vaddq_s32(sum1, sampleNExt.val[1]);
    571         }
    572         int32x2_t volumesV, outV;
    573         volumesV = vld1_s32(mVolumeSIMD);
    574         outV = vld1_s32(out);
    575 
    576         //add all 4 partial sums
    577         int32x2_t sumLow0, sumHigh0, sumLow1, sumHigh1;
    578         sumLow0 = vget_low_s32(sum0);
    579         sumHigh0 = vget_high_s32(sum0);
    580         sumLow1 = vget_low_s32(sum1);
    581         sumHigh1 = vget_high_s32(sum1);
    582         sumLow0 = vpadd_s32(sumLow0, sumHigh0);
    583         sumLow0 = vpadd_s32(sumLow0, sumLow0);
    584         sumLow1 = vpadd_s32(sumLow1, sumHigh1);
    585         sumLow1 = vpadd_s32(sumLow1, sumLow1);
    586 
    587         sumLow0 = vtrn_s32(sumLow0, sumLow1).val[0];
    588         sumLow0 = vqrdmulh_s32(sumLow0, volumesV);
    589         outV = vadd_s32(outV, sumLow0);
    590         vst1_s32(out, outV);
    591     }
    592 #endif
    593 }
    594 
    595 template<int CHANNELS>
    596 void AudioResamplerSinc::interpolate(
    597         int32_t& l, int32_t& r,
    598         const int32_t* coefs, size_t offset,
    599         int32_t lerp, const int16_t* samples)
    600 {
    601     int32_t c0 = coefs[0];
    602     int32_t c1 = coefs[offset];
    603     int32_t sinc = mulAdd(lerp, (c1-c0)<<1, c0);
    604     if (CHANNELS == 2) {
    605         uint32_t rl = *reinterpret_cast<const uint32_t*>(samples);
    606         l = mulAddRL(1, rl, sinc, l);
    607         r = mulAddRL(0, rl, sinc, r);
    608     } else {
    609         r = l = mulAdd(samples[0], sinc, l);
    610     }
    611 }
    612 // ----------------------------------------------------------------------------
    613 } // namespace android
    614