audio_utils/power.cpp

/*
 * Copyright 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// #define LOG_NDEBUG 0
#define LOG_TAG "audio_utils_power"
#include <log/log.h>

#include <algorithm>
#include <math.h>

#include <audio_utils/power.h>
#include <audio_utils/primitives.h>

#if defined(__aarch64__) || defined(__ARM_NEON__)
#include <arm_neon.h>
#define USE_NEON
#endif

namespace {

constexpr inline bool isFormatSupported(audio_format_t format) {
    switch (format) {
    case AUDIO_FORMAT_PCM_8_BIT:
    case AUDIO_FORMAT_PCM_16_BIT:
    case AUDIO_FORMAT_PCM_24_BIT_PACKED:
    case AUDIO_FORMAT_PCM_8_24_BIT:
    case AUDIO_FORMAT_PCM_32_BIT:
    case AUDIO_FORMAT_PCM_FLOAT:
        return true;
    default:
        return false;
    }
}

template <typename T>
inline T getPtrPtrValueAndIncrement(const void **data)
{
    return *(*reinterpret_cast<const T **>(data))++;
}

template <audio_format_t FORMAT>
inline float convertToFloatAndIncrement(const void **data)
{
    switch (FORMAT) {
    case AUDIO_FORMAT_PCM_8_BIT:
        return float_from_u8(getPtrPtrValueAndIncrement<uint8_t>(data));

    case AUDIO_FORMAT_PCM_16_BIT:
        return float_from_i16(getPtrPtrValueAndIncrement<int16_t>(data));

    case AUDIO_FORMAT_PCM_24_BIT_PACKED: {
        const uint8_t *uptr = reinterpret_cast<const uint8_t *>(*data);
        *data = uptr + 3;
        return float_from_p24(uptr);
    }

    case AUDIO_FORMAT_PCM_8_24_BIT:
        return float_from_q8_23(getPtrPtrValueAndIncrement<int32_t>(data));

    case AUDIO_FORMAT_PCM_32_BIT:
        return float_from_i32(getPtrPtrValueAndIncrement<int32_t>(data));

    case AUDIO_FORMAT_PCM_FLOAT:
        return getPtrPtrValueAndIncrement<float>(data);

    default:
        // static_assert cannot use false because the compiler may interpret it
        // even though this code path may never be taken.
        static_assert(isFormatSupported(FORMAT), "unsupported format");
    }
}

// used to normalize integer fixed point value to the floating point equivalent.
template <audio_format_t FORMAT>
constexpr inline float normalizeAmplitude()
{
    switch (FORMAT) {
    case AUDIO_FORMAT_PCM_8_BIT:
        return 1.f / (1 << 7);

    case AUDIO_FORMAT_PCM_16_BIT:
        return 1.f / (1 << 15);

    case AUDIO_FORMAT_PCM_24_BIT_PACKED: // fall through
    case AUDIO_FORMAT_PCM_8_24_BIT:
        return 1.f / (1 << 23);

    case AUDIO_FORMAT_PCM_32_BIT:
        return 1.f / (1U << 31);

    case AUDIO_FORMAT_PCM_FLOAT:
         return 1.f;

    default:
        // static_assert cannot use false because the compiler may interpret it
        // even though this code path may never be taken.
        static_assert(isFormatSupported(FORMAT), "unsupported format");
    }
}

template <audio_format_t FORMAT>
constexpr inline float normalizeEnergy()
{
    const float val = normalizeAmplitude<FORMAT>();
    return val * val;
}

template <audio_format_t FORMAT>
inline float energyMonoRef(const void *amplitudes, size_t size)
{
    float accum(0.f);
    for (size_t i = 0; i < size; ++i) {
        const float amplitude = convertToFloatAndIncrement<FORMAT>(&amplitudes);
        accum += amplitude * amplitude;
    }
    return accum;
}

template <audio_format_t FORMAT>
inline float energyMono(const void *amplitudes, size_t size)
{
    return energyMonoRef<FORMAT>(amplitudes, size);
}

// fast float power computation for ARM processors that support NEON.
#ifdef USE_NEON

template <typename T>
float32x4_t convertToFloatVectorAmplitude(T vamplitude) = delete;

template <>
float32x4_t convertToFloatVectorAmplitude<float32x4_t>(float32x4_t vamplitude) {
    return vamplitude;
}

template <>
float32x4_t convertToFloatVectorAmplitude<int16x4_t>(int16x4_t vamplitude) {
    const int32x4_t iamplitude = vmovl_s16(vamplitude); // expand s16 to s32 first
    return vcvtq_f32_s32(iamplitude);
}

template <>
float32x4_t convertToFloatVectorAmplitude<int32x4_t>(int32x4_t vamplitude) {
    return vcvtq_f32_s32(vamplitude);
}

template <typename Vector, typename Scalar>
inline float energyMonoVector(const void *amplitudes, size_t size)
{
    static_assert(sizeof(Vector) % sizeof(Scalar) == 0,
             "Vector size must be a multiple of scalar size");
    const size_t vectorLength = sizeof(Vector) / sizeof(Scalar); // typically 4 (a const)

    // check pointer validity, must be aligned with scalar type.
    const Scalar *samplitudes = reinterpret_cast<const Scalar *>(amplitudes);
    LOG_ALWAYS_FATAL_IF((uintptr_t)samplitudes % alignof(Scalar) != 0,
            "Non-element aligned address: %p %zu", samplitudes, alignof(Scalar));

    float accumulator = 0;

    // handle pointer unaligned to vector type.
    while ((uintptr_t)samplitudes % alignof(Vector) != 0 /* compiler optimized */ && size > 0) {
        const float amp = (float)*samplitudes++;
        accumulator += amp * amp;
        --size;
    }

    // samplitudes is now adjusted for proper vector alignment, cast to Vector *
    const Vector *vamplitudes = reinterpret_cast<const Vector *>(samplitudes);

    // clear vector accumulator
    float32x4_t accum = vdupq_n_f32(0);

    // iterate over array getting sum of squares in vectorLength lanes.
    size_t i;
    for (i = 0; i < size - size % vectorLength /* compiler optimized */; i += vectorLength) {
        const float32x4_t famplitude = convertToFloatVectorAmplitude(*vamplitudes++);
        accum = vmlaq_f32(accum, famplitude, famplitude);
    }

    // narrow vectorLength lanes of floats
    float32x2_t accum2 = vadd_f32(vget_low_f32(accum), vget_high_f32(accum)); // get stereo volume
    accum2 = vpadd_f32(accum2, accum2); // combine to mono

    // accumulate vector
    accumulator += vget_lane_f32(accum2, 0);

    // accumulate any trailing elements too small for vector size
    for (; i < size; ++i) {
        const float amp = (float)samplitudes[i];
        accumulator += amp * amp;
    }
    return accumulator;
}

template <>
inline float energyMono<AUDIO_FORMAT_PCM_FLOAT>(const void *amplitudes, size_t size)
{
    return energyMonoVector<float32x4_t, float>(amplitudes, size);
}

template <>
inline float energyMono<AUDIO_FORMAT_PCM_16_BIT>(const void *amplitudes, size_t size)
{
    return energyMonoVector<int16x4_t, int16_t>(amplitudes, size)
            * normalizeEnergy<AUDIO_FORMAT_PCM_16_BIT>();
}

// fast int32_t power computation for PCM_32
template <>
inline float energyMono<AUDIO_FORMAT_PCM_32_BIT>(const void *amplitudes, size_t size)
{
    return energyMonoVector<int32x4_t, int32_t>(amplitudes, size)
            * normalizeEnergy<AUDIO_FORMAT_PCM_32_BIT>();
}

// fast int32_t power computation for PCM_8_24 (essentially identical to PCM_32 above)
template <>
inline float energyMono<AUDIO_FORMAT_PCM_8_24_BIT>(const void *amplitudes, size_t size)
{
    return energyMonoVector<int32x4_t, int32_t>(amplitudes, size)
            * normalizeEnergy<AUDIO_FORMAT_PCM_8_24_BIT>();
}

#endif // USE_NEON

} // namespace

float audio_utils_compute_energy_mono(const void *buffer, audio_format_t format, size_t samples)
{
    switch (format) {
    case AUDIO_FORMAT_PCM_8_BIT:
        return energyMono<AUDIO_FORMAT_PCM_8_BIT>(buffer, samples);

    case AUDIO_FORMAT_PCM_16_BIT:
        return energyMono<AUDIO_FORMAT_PCM_16_BIT>(buffer, samples);

    case AUDIO_FORMAT_PCM_24_BIT_PACKED:
        return energyMono<AUDIO_FORMAT_PCM_24_BIT_PACKED>(buffer, samples);

    case AUDIO_FORMAT_PCM_8_24_BIT:
        return energyMono<AUDIO_FORMAT_PCM_8_24_BIT>(buffer, samples);

    case AUDIO_FORMAT_PCM_32_BIT:
        return energyMono<AUDIO_FORMAT_PCM_32_BIT>(buffer, samples);

    case AUDIO_FORMAT_PCM_FLOAT:
        return energyMono<AUDIO_FORMAT_PCM_FLOAT>(buffer, samples);

    default:
        LOG_ALWAYS_FATAL("invalid format: %#x", format);
    }
}

float audio_utils_compute_power_mono(const void *buffer, audio_format_t format, size_t samples)
{
    return audio_utils_power_from_energy(
            audio_utils_compute_energy_mono(buffer, format, samples) / samples);
}

bool audio_utils_is_compute_power_format_supported(audio_format_t format)
{
    return isFormatSupported(format);
}