audio_sample.cpp

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#include "pfc.h"

namespace audio_math {
    audio_sample decodeFloat24ptr(const void * sourcePtr) {
        PFC_STATIC_ASSERT(pfc::byte_order_is_little_endian);
        union {
            uint8_t bytes[4];
            float v;
        } u;
        const uint8_t * s = reinterpret_cast<const uint8_t*>(sourcePtr);
        u.bytes[0] = 0;
        u.bytes[1] = s[0];
        u.bytes[2] = s[1];
        u.bytes[3] = s[2];
        return u.v;
    }
    audio_sample decodeFloat24ptrbs(const void * sourcePtr) {
        PFC_STATIC_ASSERT(pfc::byte_order_is_little_endian);
        union {
            uint8_t bytes[4];
            float v;
        } u;
        const uint8_t * s = reinterpret_cast<const uint8_t*>(sourcePtr);
        u.bytes[0] = 0;
        u.bytes[1] = s[2];
        u.bytes[2] = s[1];
        u.bytes[3] = s[0];
        return u.v;
    }

    audio_sample decodeFloat16(uint16_t source) {
        const unsigned fractionBits = 10;
        const unsigned widthBits = 16;
        typedef uint16_t source_t;

    /*  typedef uint64_t out_t; typedef double retval_t;
        enum { 
            outExponent = 11, 
            outFraction = 52, 
            outExponentShift = (1 << (outExponent-1))-1 
        };*/

        typedef uint32_t out_t; typedef float retval_t;
        enum { 
            outExponent = 8, 
            outFraction = 23, 
            outExponentShift = (1 << (outExponent-1))-1 
        };

        const unsigned exponentBits = widthBits - fractionBits - 1;
        // 1 bit sign | exponent | fraction
        source_t fraction = source & (((source_t)1 << fractionBits)-1);
        source >>= fractionBits;
        int exponent = (int)( source & (((source_t)1 << exponentBits)-1) ) - (int)((1 << (exponentBits-1))-1);
        source >>= exponentBits;

        if (outExponent + outExponentShift <= 0) return 0;

        out_t output = (out_t)( source&1 );
        output <<= outExponent;
        output |= (unsigned) (exponent + outExponentShift) & ( (1<<outExponent) - 1 );
        output <<= outFraction;
        int shift = (int) outFraction - (int) fractionBits;
        if (shift < 0) output |= (out_t) (fraction >> -shift);
        else output |= (out_t) (fraction << shift);
        return *(retval_t*)&output / float16scale;
    }
}