core/uhjfilter.h

   1 #ifndef CORE_UHJFILTER_H
   2 #define CORE_UHJFILTER_H
   3
   4 #include <array>
   5
   6 #include "almalloc.h"
   7 #include "alspan.h"
   8 #include "bufferline.h"
   9 #include "resampler_limits.h"
  10
  11
  12 struct DecoderBase {
  13     virtual ~DecoderBase() = default;
  14
  15     virtual void decode(const al::span<float*> samples, const size_t samplesToDo,
  16         const size_t forwardSamples) = 0;
  17
  18     /**
  19      * The width factor for Super Stereo processing. Can be changed in between
  20      * calls to decode, with valid values being between 0...0.7.
  21      */
  22     float mWidthControl{0.593f};
  23
  24     float mCurrentWidth{-1.0f};
  25 };
  26
  27
  28 struct UhjFilterBase {
  29     /* The filter delay is half it's effective size, so a delay of 128 has a
  30      * FIR length of 256.
  31      */
  32     static constexpr size_t sFilterDelay{128};
  33 };
  34
  35 struct UhjEncoder : public UhjFilterBase {
  36     /* Delays and processing storage for the unfiltered signal. */
  37     alignas(16) std::array<float,BufferLineSize+sFilterDelay> mS{};
  38     alignas(16) std::array<float,BufferLineSize+sFilterDelay> mD{};
  39
  40     /* History for the FIR filter. */
  41     alignas(16) std::array<float,sFilterDelay*2 - 1> mWXHistory{};
  42
  43     alignas(16) std::array<float,BufferLineSize + sFilterDelay*2> mTemp{};
  44
  45     /**
  46      * Encodes a 2-channel UHJ (stereo-compatible) signal from a B-Format input
  47      * signal. The input must use FuMa channel ordering and UHJ scaling (FuMa
  48      * with an additional +3dB boost).
  49      */
  50     void encode(float *LeftOut, float *RightOut, const al::span<const float*const,3> InSamples,
  51         const size_t SamplesToDo);
  52
  53     DEF_NEWDEL(UhjEncoder)
  54 };
  55
  56
  57 struct UhjDecoder : public DecoderBase, public UhjFilterBase {
  58     /* For 2-channel UHJ, shelf filters should use these LF responses. */
  59     static constexpr float sWLFScale{0.661f};
  60     static constexpr float sXYLFScale{1.293f};
  61
  62     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mS{};
  63     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mD{};
  64     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mT{};
  65
  66     alignas(16) std::array<float,sFilterDelay-1> mDTHistory{};
  67     alignas(16) std::array<float,sFilterDelay-1> mSHistory{};
  68
  69     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge + sFilterDelay*2> mTemp{};
  70
  71     /**
  72      * Decodes a 3- or 4-channel UHJ signal into a B-Format signal with FuMa
  73      * channel ordering and UHJ scaling. For 3-channel, the 3rd channel may be
  74      * attenuated by 'n', where 0 <= n <= 1. So to decode 2-channel UHJ, supply
  75      * 3 channels with the 3rd channel silent (n=0). The B-Format signal
  76      * reconstructed from 2-channel UHJ should not be run through a normal
  77      * B-Format decoder, as it needs different shelf filters.
  78      */
  79     void decode(const al::span<float*> samples, const size_t samplesToDo,
  80         const size_t forwardSamples) override;
  81
  82     DEF_NEWDEL(UhjDecoder)
  83 };
  84
  85 struct UhjStereoDecoder : public UhjDecoder {
  86     /**
  87      * Applies Super Stereo processing on a stereo signal to create a B-Format
  88      * signal with FuMa channel ordering and UHJ scaling. The samples span
  89      * should contain 3 channels, the first two being the left and right stereo
  90      * channels, and the third left empty.
  91      */
  92     void decode(const al::span<float*> samples, const size_t samplesToDo,
  93         const size_t forwardSamples) override;
  94
  95     DEF_NEWDEL(UhjStereoDecoder)
  96 };
  97
  98 #endif /* CORE_UHJFILTER_H */