Method encodeAiffSampleRate

AudioFile.h:1581–1611

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//=============================================================
inline void AiffUtilities::encodeAiffSampleRate (double sampleRate, uint8_t* bytes)
{
    // Determine the sign
    int sign = (sampleRate < 0) ? -1 : 1;
    
    if (sign == -1)
        sampleRate = -sampleRate;
    
    // Set most significant bit of byte 0 for the sign
    bytes[0] = (sign == -1) ? 0x80 : 0x00;
    
    // Calculate the exponent using logarithm (log base 2)
    int exponent = (log (sampleRate) / log (2.0));
    
    // Add bias to exponent for AIFF
    uint16_t biasedExponent = static_cast<uint16_t> (exponent + 16383);
    
    // Normalize the sample rate
    double normalizedSampleRate = sampleRate / pow (2.0, exponent);
    
    // Calculate the mantissa
    uint64_t mantissa = static_cast<uint64_t> (normalizedSampleRate * (1ULL << 63));
    
    // Pack the exponent into first two bytes of 10-byte AIFF format
    bytes[0] |= (biasedExponent >> 8) & 0x7F;   // Upper 7 bits of exponent
    bytes[1] = biasedExponent & 0xFF;           // Lower 8 bits of exponent
    
    // Put the mantissa into byte array
    for (int i = 0; i < 8; ++i)
        bytes[2 + i] = (mantissa >> (8 * (7 - i))) & 0xFF;
}

#if defined (_MSC_VER)
    __pragma(warning (pop))