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 setWidth(float width) noexcept = 0;
  16
  17     virtual void decode(const al::span<float*> samples, const size_t samplesToDo,
  18         const size_t forwardSamples) = 0;
  19 };
  20
  21
  22 struct UhjFilterBase {
  23     /* The filter delay is half it's effective size, so a delay of 128 has a
  24      * FIR length of 256.
  25      */
  26     static constexpr size_t sFilterDelay{128};
  27 };
  28
  29 struct UhjEncoder : public UhjFilterBase {
  30     /* Delays and processing storage for the unfiltered signal. */
  31     alignas(16) std::array<float,BufferLineSize+sFilterDelay> mS{};
  32     alignas(16) std::array<float,BufferLineSize+sFilterDelay> mD{};
  33
  34     /* History for the FIR filter. */
  35     alignas(16) std::array<float,sFilterDelay*2 - 1> mWXHistory{};
  36
  37     alignas(16) std::array<float,BufferLineSize + sFilterDelay*2> mTemp{};
  38
  39     /**
  40      * Encodes a 2-channel UHJ (stereo-compatible) signal from a B-Format input
  41      * signal. The input must use FuMa channel ordering and UHJ scaling (FuMa
  42      * with an additional +3dB boost).
  43      */
  44     void encode(float *LeftOut, float *RightOut, const al::span<const float*const,3> InSamples,
  45         const size_t SamplesToDo);
  46
  47     DEF_NEWDEL(UhjEncoder)
  48 };
  49
  50
  51 struct UhjDecoder : public DecoderBase, public UhjFilterBase {
  52     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mS{};
  53     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mD{};
  54     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge+sFilterDelay> mT{};
  55
  56     alignas(16) std::array<float,sFilterDelay-1> mDTHistory{};
  57     alignas(16) std::array<float,sFilterDelay-1> mSHistory{};
  58
  59     alignas(16) std::array<float,BufferLineSize+MaxResamplerEdge + sFilterDelay*2> mTemp{};
  60
  61     void setWidth(float) noexcept override { }
  62
  63     /**
  64      * Decodes a 3- or 4-channel UHJ signal into a B-Format signal with FuMa
  65      * channel ordering and UHJ scaling. For 3-channel, the 3rd channel may be
  66      * attenuated by 'n', where 0 <= n <= 1. So to decode 2-channel UHJ, supply
  67      * 3 channels with the 3rd channel silent (n=0). The B-Format signal
  68      * reconstructed from 2-channel UHJ should not be run through a normal
  69      * B-Format decoder, as it needs different shelf filters.
  70      */
  71     void decode(const al::span<float*> samples, const size_t samplesToDo,
  72         const size_t forwardSamples) override;
  73
  74     DEF_NEWDEL(UhjDecoder)
  75 };
  76
  77 struct UhjStereoDecoder : public UhjDecoder {
  78     float mCurrentWidth{-1.0f};
  79
  80     /**
  81      * The width factor for Super Stereo processing. Can be changed in between
  82      * calls to decodeStereo, with valid values being between 0...0.7.
  83      */
  84     float mWidthControl{0.593f};
  85
  86     void setWidth(float width) noexcept override
  87     { mWidthControl = width; }
  88
  89     /**
  90      * Applies Super Stereo processing on a stereo signal to create a B-Format
  91      * signal with FuMa channel ordering and UHJ scaling. The samples span
  92      * should contain 3 channels, the first two being the left and right stereo
  93      * channels, and the third left empty.
  94      */
  95     void decode(const al::span<float*> samples, const size_t samplesToDo,
  96         const size_t forwardSamples) override;
  97
  98     DEF_NEWDEL(UhjStereoDecoder)
  99 };
 100
 101 #endif /* CORE_UHJFILTER_H */