serenity/Userland/Libraries/LibAudio/Buffer.h

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/ByteBuffer.h>
#include <AK/Math.h>
#include <AK/MemoryStream.h>
#include <AK/String.h>
#include <AK/Types.h>
#include <AK/Vector.h>
#include <LibCore/AnonymousBuffer.h>
#include <string.h>

namespace Audio {
using namespace AK::Exponentials;

// Constants for logarithmic volume. See Frame::operator*
// Corresponds to 60dB
constexpr double DYNAMIC_RANGE = 1000;
constexpr double VOLUME_A = 1 / DYNAMIC_RANGE;
double const VOLUME_B = log(DYNAMIC_RANGE);

// A single sample in an audio buffer.
// Values are floating point, and should range from -1.0 to +1.0
struct Frame {
    constexpr Frame() = default;

    // For mono
    constexpr Frame(double left)
        : left(left)
        , right(left)
    {
    }

    // For stereo
    constexpr Frame(double left, double right)
        : left(left)
        , right(right)
    {
    }

    void clip()
    {
        if (left > 1)
            left = 1;
        else if (left < -1)
            left = -1;

        if (right > 1)
            right = 1;
        else if (right < -1)
            right = -1;
    }

    // Logarithmic scaling, as audio should ALWAYS do.
    // Reference: https://www.dr-lex.be/info-stuff/volumecontrols.html
    // We use the curve `factor = a * exp(b * change)`,
    // where change is the input fraction we want to change by,
    // a = 1/1000, b = ln(1000) = 6.908 and factor is the multiplier used.
    // The value 1000 represents the dynamic range in sound pressure, which corresponds to 60 dB(A).
    // This is a good dynamic range because it can represent all loudness values from
    // 30 dB(A) (barely hearable with background noise)
    // to 90 dB(A) (almost too loud to hear and about the reasonable limit of actual sound equipment).
    //
    // Format ranges:
    // - Linear:        0.0 to 1.0
    // - Logarithmic:   0.0 to 1.0

    ALWAYS_INLINE double linear_to_log(double const change)
    {
        // TODO: Add linear slope around 0
        return VOLUME_A * exp(VOLUME_B * change);
    }

    ALWAYS_INLINE double log_to_linear(double const val)
    {
        // TODO: Add linear slope around 0
        return log(val / VOLUME_A) / VOLUME_B;
    }

    ALWAYS_INLINE Frame& log_multiply(double const change)
    {
        double factor = linear_to_log(change);
        left *= factor;
        right *= factor;
        return *this;
    }

    ALWAYS_INLINE Frame log_multiplied(double const volume_change) const
    {
        Frame new_frame { left, right };
        new_frame.log_multiply(volume_change);
        return new_frame;
    }

    ALWAYS_INLINE Frame& log_pan(double const pan)
    {
        left *= linear_to_log(min(pan * -1 + 1.0, 1.0));
        right *= linear_to_log(min(pan + 1.0, 1.0));
        return *this;
    }

    ALWAYS_INLINE Frame log_pan(double const pan) const
    {
        Frame new_frame { left, right };
        new_frame.log_pan(pan);
        return new_frame;
    }

    constexpr Frame& operator*=(double const mult)
    {
        left *= mult;
        right *= mult;
        return *this;
    }

    constexpr Frame operator*(double const mult)
    {
        return { left * mult, right * mult };
    }

    constexpr Frame& operator+=(Frame const& other)
    {
        left += other.left;
        right += other.right;
        return *this;
    }
    constexpr Frame& operator+=(double other)
    {
        left += other;
        right += other;
        return *this;
    }

    constexpr Frame operator+(Frame const& other)
    {
        return { left + other.left, right + other.right };
    }

    double left { 0 };
    double right { 0 };
};

// Supported PCM sample formats.
enum PcmSampleFormat : u8 {
    Uint8,
    Int16,
    Int24,
    Int32,
    Float32,
    Float64,
};

// Most of the read code only cares about how many bits to read or write
u16 pcm_bits_per_sample(PcmSampleFormat format);
String sample_format_name(PcmSampleFormat format);

// Small helper to resample from one playback rate to another
// This isn't really "smart", in that we just insert (or drop) samples.
// Should do better...
template<typename SampleType>
class ResampleHelper {
public:
    ResampleHelper(u32 source, u32 target);

    // To be used as follows:
    // while the resampler doesn't need a new sample, read_sample(current) and store the resulting samples.
    // as long as the resampler needs a new sample, process_sample(current)

    // Stores a new sample
    void process_sample(SampleType sample_l, SampleType sample_r);
    // Assigns the given sample to its correct value and returns false if there is a new sample required
    bool read_sample(SampleType& next_l, SampleType& next_r);
    Vector<SampleType> resample(Vector<SampleType> to_resample);

    void reset();

    u32 source() const { return m_source; }
    u32 target() const { return m_target; }

private:
    const u32 m_source;
    const u32 m_target;
    u32 m_current_ratio { 0 };
    SampleType m_last_sample_l;
    SampleType m_last_sample_r;
};

// A buffer of audio samples.
class Buffer : public RefCounted<Buffer> {
public:
    static RefPtr<Buffer> from_pcm_data(ReadonlyBytes data, int num_channels, PcmSampleFormat sample_format);
    static RefPtr<Buffer> from_pcm_stream(InputMemoryStream& stream, int num_channels, PcmSampleFormat sample_format, int num_samples);
    static NonnullRefPtr<Buffer> create_with_samples(Vector<Frame>&& samples)
    {
        return adopt_ref(*new Buffer(move(samples)));
    }
    static NonnullRefPtr<Buffer> create_with_anonymous_buffer(Core::AnonymousBuffer buffer, i32 buffer_id, int sample_count)
    {
        return adopt_ref(*new Buffer(move(buffer), buffer_id, sample_count));
    }

    const Frame* samples() const { return (const Frame*)data(); }
    int sample_count() const { return m_sample_count; }
    const void* data() const { return m_buffer.data<void>(); }
    int size_in_bytes() const { return m_sample_count * (int)sizeof(Frame); }
    int id() const { return m_id; }
    const Core::AnonymousBuffer& anonymous_buffer() const { return m_buffer; }

private:
    explicit Buffer(const Vector<Frame> samples)
        : m_buffer(Core::AnonymousBuffer::create_with_size(samples.size() * sizeof(Frame)).release_value())
        , m_id(allocate_id())
        , m_sample_count(samples.size())
    {
        memcpy(m_buffer.data<void>(), samples.data(), samples.size() * sizeof(Frame));
    }

    explicit Buffer(Core::AnonymousBuffer buffer, i32 buffer_id, int sample_count)
        : m_buffer(move(buffer))
        , m_id(buffer_id)
        , m_sample_count(sample_count)
    {
    }

    static i32 allocate_id();

    Core::AnonymousBuffer m_buffer;
    const i32 m_id;
    const int m_sample_count;
};

// This only works for double resamplers, and therefore cannot be part of the class
NonnullRefPtr<Buffer> resample_buffer(ResampleHelper<double>& resampler, Buffer const& to_resample);

}