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Thread: FIR taps and use of CMSIS arm_fir_q15

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  1. #1
    Junior Member
    Join Date
    Dec 2016
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    2

    FIR taps and use of CMSIS arm_fir_q15

    Hey all,

    1. New here, haven't even ordered hardware yet.
    2. I did some forum searching before asking the question, to not reinvent the wheel
    3. I posed this question to Paul back during Teensy 3.6 Kickstarter, and he suggested I post it here.


    Background:
    A very common FIR filter size used in the pro audio world is 384 taps at 48kHz sample rate with 16 bit depth. I want to see if the Teensy 3.6 can process an FIR this big in real time, be it in integer or floating point. I have attached an Excel file with a representative set of taps (taken from a correction curve applied at a real event).

    Questions:
    1. Can someone test these filter taps for me to see the processing overhead on a 3.6?
    2. Looking at the CMSIS documentation, there is a function "arm_fir_q15" which has a 64bit accumulator. Can I simply swap this into "Filter_Fir"? I'd rather not have to apply 8 bits of input scaling to keep the accumulator from wrapping.
    3. How much performance penalty is there for using "arm_fir_q15" versus "arm_fir_fast_q15"


    Hello, and thanks in advance,
    Attached Files Attached Files

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