Method decodeAiffSampleRate

AudioFile.h:1538–1578

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//=============================================================
inline double AiffUtilities::decodeAiffSampleRate (const uint8_t* bytes)
{
    // Note: Sample rate is 80 bits made up of
    // * 1 sign bit
    // * 15 exponent bits
    // * 64 mantissa bits
    
    // ----------------------------------------------
    // Sign
    
    // Extract the sign (most significant bit of byte 0)
    int sign = (bytes[0] & 0x80) ? -1 : 1;
    
    // ----------------------------------------------
    // Exponent
    
    // byte 0: ignore the sign and shift the most significant bits to the left by one byte
    uint16_t msbShifted = (static_cast<uint16_t> (bytes[0] & 0x7F) << 8);
    
    // calculate exponent by combining byte 0 and byte 1 and subtract bias
    uint16_t exponent = (msbShifted | static_cast<uint16_t> (bytes[1])) - 16383;
    
    // ----------------------------------------------
    // Mantissa
    
    // Extract the mantissa (remaining 64 bits) by looping over the remaining
    // bytes and combining them while shifting the result to the left by
    // 8 bits each time
    uint64_t mantissa = 0;
    
    for (int i = 2; i < 10; ++i)
        mantissa = (mantissa << 8) | bytes[i];
    
    // Normalize the mantissa (implicit leading 1 for normalized values)
    double normalisedMantissa = static_cast<double> (mantissa) / (1ULL << 63);
    
    // ----------------------------------------------
    // Combine sign, exponent, and mantissa into a double
    
    return sign * std::ldexp (normalisedMantissa, exponent);
}

//=============================================================
inline void AiffUtilities::encodeAiffSampleRate (double sampleRate, uint8_t* bytes)