RealFFT

Initialization function for the Q15 RFFT/RIFFT.

Parameters:

[in,out]	*S	points to an instance of the Q15 RFFT/RIFFT structure.
[in]	fftLenReal	length of the FFT.
[in]	ifftFlagR	flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform.
[in]	bitReverseFlag	flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.

Returns:

The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if fftLenReal is not a supported value.

Description:

The parameter fftLenReal Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192.

The parameter ifftFlagR controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated.

The parameter bitReverseFlag controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.

This function also initializes Twiddle factor table.

Definition at line 2154 of file arm_rfft_init_q15.c.

Processing function for the Q15 RFFT/RIFFT.

Parameters:

[in]	*S	points to an instance of the Q15 RFFT/RIFFT structure.
[in]	*pSrc	points to the input buffer.
[out]	*pDst	points to the output buffer.

Returns:

none.

Input an output formats:

Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process. Hence the output format is different for different RFFT sizes. The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:

Input and Output Formats for Q15 RFFT

Input and Output Formats for Q15 RIFFT

Definition at line 74 of file arm_rfft_q15.c.