Thread: Understanding the Code

  1. #1
    Registered User
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    Apr 2019
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    Understanding the Code

    I saw the code
    Code:
    typedef signed int SFRAC16;
    #define Q15(Float_Value)    \
            ((Float_Value < 0.0) ? (SFRAC16)(32768 * (Float_Value) - 0.5) \
            : (SFRAC16)(32767 * (Float_Value) + 0.5))
    What is the significance of 0.5? Does 0.5 signify any midpoint?

  2. #2
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    This code is a slightly questionable attempt at rounding into a 16 bit signed output. I say questionable because depending on "Float_Value", this could overflow.

    The 0.5 is a means of 5/4 rounding of the result into an integer.

    This also makes the assumption, it appears, that at singed int is 16 bits, but that's not guaranteed.
    Last edited by Niccolo; 10-02-2019 at 11:32 AM.

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