Duckstation/dep/freesurround/include/freesurround_decoder.h

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2024-04-16 06:55:09 +00:00
// SPDX-FileCopyrightText: 2007-2010 Christian Kothe, 2024 Connor McLaughlin <stenzek@gmail.com>
// SPDX-License-Identifier: GPL-2.0+
#pragma once
#include "kiss_fftr.h"
#include <array>
#include <cmath>
#include <complex>
#include <span>
#include <vector>
/**
* The FreeSurround decoder.
*/
class FreeSurroundDecoder
{
public:
/**
* The supported output channel setups.
* A channel setup is defined by the set of channels that are present. Here is a graphic
* of the cs_5point1 setup: http://en.wikipedia.org/wiki/File:5_1_channels_(surround_sound)_label.svg
*/
enum class ChannelSetup
{
Stereo,
Surround41,
Surround51,
Surround71,
Legacy, // same channels as cs_5point1 but different upmixing transform; does not support the focus control
MaxCount
};
static constexpr int grid_res = 21; // resolution of the lookup grid
using LUT = const float (*)[grid_res];
/**
* Create an instance of the decoder.
* @param setup The output channel setup -- determines the number of output channels
* and their place in the sound field.
* @param blocksize Granularity at which data is processed by the decode() function.
* Must be a power of two and should correspond to ca. 10ms worth of single-channel
* samples (default is 4096 for 44.1Khz data). Do not make it shorter or longer
* than 5ms to 20ms since the granularity at which locations are decoded
* changes with this.
*/
FreeSurroundDecoder(ChannelSetup setup = ChannelSetup::Surround51, unsigned blocksize = 4096);
~FreeSurroundDecoder();
/**
* Decode a chunk of stereo sound. The output is delayed by half of the blocksize.
* This function is the only one needed for straightforward decoding.
* @param input Contains exactly blocksize (multiplexed) stereo samples, i.e. 2*blocksize numbers.
* @return A pointer to an internal buffer of exactly blocksize (multiplexed) multichannel samples.
* The actual number of values depends on the number of output channels in the chosen
* channel setup.
*/
float* Decode(float* input);
/**
* Flush the internal buffer.
*/
void Flush();
// --- soundfield transformations
// These functions allow to set up geometric transformations of the sound field after it has been decoded.
// The sound field is best pictured as a 2-dimensional square with the listener in its
// center which can be shifted or stretched in various ways before it is sent to the
// speakers. The order in which these transformations are applied is as listed below.
/**
* Allows to wrap the soundfield around the listener in a circular manner.
* Determines the angle of the frontal sound stage relative to the listener, in degrees.
* A setting of 90° corresponds to standard surround decoding, 180° stretches the front stage from
* ear to ear, 270° wraps it around most of the head. The side and rear content of the sound
* field is compressed accordingly behind the listerer. (default: 90, range: [0°..360°])
*/
void SetCircularWrap(float v);
/**
* Allows to shift the soundfield forward or backward.
* Value range: [-1.0..+1.0]. 0 is no offset, positive values move the sound
* forward, negative values move it backwards. (default: 0)
*/
void SetShift(float v);
/**
* Allows to scale the soundfield backwards.
* Value range: [0.0..+5.0] -- 0 is all compressed to the front, 1 is no change, 5 is scaled 5x backwards (default: 1)
*/
void SetDepth(float v);
/**
* Allows to control the localization (i.e., focality) of sources.
* Value range: [-1.0..+1.0] -- 0 means unchanged, positive means more localized, negative means more ambient
* (default: 0)
*/
void SetFocus(float v);
// --- rendering parameters
// These parameters control how the sound field is mapped onto speakers.
/**
* Set the presence of the front center channel(s).
* Value range: [0.0..1.0] -- fully present at 1.0, fully replaced by left/right at 0.0 (default: 1).
* The default of 1.0 results in spec-conformant decoding ("movie mode") while a value of 0.7 is
* better suited for music reproduction (which is usually mixed without a center channel).
*/
void SetCenterImage(float v);
/**
* Set the front stereo separation.
* Value range: [0.0..inf] -- 1.0 is default, 0.0 is mono.
*/
void SetFrontSeparation(float v);
/**
* Set the rear stereo separation.
* Value range: [0.0..inf] -- 1.0 is default, 0.0 is mono.
*/
void SetRearSeparation(float v);
// --- bass redirection (to LFE)
/**
* Enable/disable LFE channel (default: false = disabled)
*/
void SetBassRedirection(bool v);
/**
* Set the lower end of the transition band, in Hz/Nyquist (default: 40/22050).
*/
void SetLowCutoff(float v);
/**
* Set the upper end of the transition band, in Hz/Nyquist (default: 90/22050).
*/
void SetHighCutoff(float v);
// --- info
/**
* Number of samples currently held in the buffer.
*/
unsigned GetSamplesBuffered();
private:
using cplx = std::complex<double>;
struct ChannelMap
{
std::span<const LUT> luts;
const float* xsf;
};
static const std::array<ChannelMap, static_cast<size_t>(ChannelSetup::MaxCount)> s_channel_maps;
void BufferedDecode(float* input);
// get the index (and fractional offset!) in a piecewise-linear channel allocation grid
static int MapToGrid(double& x);
// constants
const ChannelMap& cmap; // the channel setup
unsigned N, C; // number of samples per input/output block, number of output channels
// parameters
float circular_wrap; // angle of the front soundstage around the listener (90°=default)
float shift; // forward/backward offset of the soundstage
float depth; // backward extension of the soundstage
float focus; // localization of the sound events
float center_image; // presence of the center speaker
float front_separation; // front stereo separation
float rear_separation; // rear stereo separation
float lo_cut, hi_cut; // LFE cutoff frequencies
bool use_lfe; // whether to use the LFE channel
// FFT data structures
std::vector<double> lt, rt, dst; // left total, right total (source arrays), time-domain destination buffer array
std::vector<cplx> lf, rf; // left total / right total in frequency domain
kiss_fftr_cfg forward = nullptr;
kiss_fftr_cfg inverse = nullptr; // FFT buffers
// buffers
bool buffer_empty = true; // whether the buffer is currently empty or dirty
std::vector<float> inbuf; // stereo input buffer (multiplexed)
std::vector<float> outbuf; // multichannel output buffer (multiplexed)
std::vector<double> wnd; // the window function, precomputed
std::vector<std::vector<cplx>> signal; // the signal to be constructed in every channel, in the frequency domain
};