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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_MIXERS_MIXER_UTILS_H_
#define SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_MIXERS_MIXER_UTILS_H_
#include <limits>
#include <type_traits>
namespace mojo {
namespace media {
namespace audio {
namespace mixers {
namespace utils {
// mixer_utils.h is a collection of inline templated utility functions meant to
// be used by mixer implementations and expanded/optimized at compile time in
// order to produce efficient inner mixing loops for all of the different
// variations of source/destination sample type/channel counts.
// Template to read samples and normalize them into signed 32 bit integers.
template <typename SType, typename Enable = void> class SampleNormalizer;
template <typename SType>
class SampleNormalizer<
SType,
typename std::enable_if<
std::is_same<SType, uint8_t>::value,
void>::type> {
public:
static inline int32_t Read(const SType* src) {
register SType tmp = *src;
return (static_cast<int32_t>(tmp) << 8) - 0x8000;
}
};
template <typename SType>
class SampleNormalizer<
SType,
typename std::enable_if<
std::is_same<SType, int16_t>::value,
void>::type> {
public:
static inline int32_t Read(const SType* src) {
return static_cast<int32_t>(*src);
}
};
// Template to read normalized source samples, and combine channels if required.
template <typename SType,
size_t SChCount,
size_t DChCount,
typename Enable = void>
class SrcReader;
template <typename SType,
size_t SChCount,
size_t DChCount>
class SrcReader<SType, SChCount, DChCount,
typename std::enable_if<
(SChCount == DChCount) ||
((SChCount == 1) && (DChCount == 2)),
void>::type> {
public:
static constexpr size_t DstPerSrc = DChCount / SChCount;
static inline int32_t Read(const SType* src) {
return SampleNormalizer<SType>::Read(src);
}
};
template <typename SType,
size_t SChCount,
size_t DChCount>
class SrcReader<SType, SChCount, DChCount,
typename std::enable_if<
(SChCount == 2) && (DChCount == 1),
void>::type> {
public:
static constexpr size_t DstPerSrc = 1;
static inline int32_t Read(const SType* src) {
return (SampleNormalizer<SType>::Read(src + 0) +
SampleNormalizer<SType>::Read(src + 1)) >> 1;
}
};
// Template to produce destination samples from normalized samples.
template <typename DType, typename Enable = void> class DstConverter;
template <typename DType>
class DstConverter<DType,
typename std::enable_if<
std::is_same<DType, int16_t>::value,
void>::type> {
public:
static inline DType Convert(int32_t sample) {
return static_cast<DType>(sample);
}
};
template <typename DType>
class DstConverter<DType,
typename std::enable_if<
std::is_same<DType, uint8_t>::value,
void>::type> {
public:
static inline DType Convert(int32_t sample) {
return static_cast<DType>((sample >> 8) + 0x80);
}
};
// Template to mix destination samples with normalized source samples based on
// accumulation policy.
template <typename DType,
bool DoAccumulate,
typename Enable = void>
class DstMixer;
template <typename DType,
bool DoAccumulate>
class DstMixer<DType, DoAccumulate,
typename std::enable_if<
DoAccumulate == false,
void>::type> {
public:
static inline int32_t Mix(const DType* dst, uint32_t sample) {
return DstConverter<DType>::Convert(sample);
}
};
template <typename DType,
bool DoAccumulate>
class DstMixer<DType, DoAccumulate,
typename std::enable_if<
DoAccumulate == true,
void>::type> {
public:
static inline int32_t Mix(const DType* dst, int32_t sample) {
sample += SampleNormalizer<DType>::Read(dst);
if (sample > std::numeric_limits<int16_t>::max()) {
return DstConverter<DType>::Convert(std::numeric_limits<int16_t>::max());
} else if (sample < std::numeric_limits<int16_t>::min()) {
return DstConverter<DType>::Convert(std::numeric_limits<int16_t>::min());
} else {
return DstConverter<DType>::Convert(sample);
}
}
};
} // namespace utils
} // namespace mixers
} // namespace audio
} // namespace media
} // namespace mojo
#endif // SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_MIXERS_MIXER_UTILS_H_