Conditions for Code Replacement of DSP System Objects with QHL

Each DSP System object™ that can be used with the Support Package for Qualcomm Hexagon processors requires specific conditions to allow code replacement with the Qualcomm Hexagon Library (QHL). You use this code replacement when generating C code from a model. The Qualcomm Hexagon Library (QHL) supports these DSP System object only when you set specific properties, as indicated in the following table.

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DSP System Object	Input Requirements	Parameter Requirements	Equivalent Functions in Replacement
dsp.FIRFilter (DSP System Toolbox)	Real values. single data type Input size must be even	Structure: Direct Form. NumeratorSource:: Property or Input port. Any frame-length if filter-length > 24. (or) 8 <= frame-length <=64 if 16<=filter length <=24	mw_qhdsp_fir_af
dsp.FIRDecimator (DSP System Toolbox)	Real values. single data type Input size must be even	Structure: Direct Form. NumeratorSource:: Property or Input port or Auto. Decimation Factor: 2,3,4 AllowArbitraryInputLength: false Decimation Factor: 2 or 3 AND FrameLength > 10 AND FilterLength >10.(or) Decimation Factor: 4 AND FilterLength < 40	mw_qhdsp_decim_af
dsp.FFT (DSP System Toolbox)	Real values. single data type Input size must be in powers of 2 Real : 16,32, …. Complex: 8,16,...	FFTImplementation: Auto BitReversedOutput: false FFTLength : <same as input length > (If FFTLengthSource is set to Property) For real FFT optimized code replacement function: All arrays must be aligned by 8 bytes. Number of input samples must be greater than or equal to 16. Use additional intermediate buffers as arguments.	Real FFT mw_qhdsp_fft_gen_twiddles_real_acf mw_qhdsp_acf_r1dfft_af For Hexagon SDK 5.5.0.0 and above, use mw_qhdsp_acf_r1dfft_af_opt (since R2026a) Complex FFT mw_qhdsp_fft_gen_twiddles_complex_acf mw_qhdsp_c1dfft_acf
dsp.IFFT (DSP System Toolbox)	single data type. Complex input values. Input size must be in powers of 2. Real : 32, 64 …. Complex: 16, 32...	FFT Length: same as input length (FFTLengthSource: is set to Property) Bit reversed order: false	Real FFT mw_qhdsp_fft_gen_twiddles_real_acf mw_qhdsp_af_r1difft_acf Complex FFT mw_qhdsp_fft_gen_twiddles_complex_acf mw_qhdsp_c1idfft_acf
dsp.SOSFilter (DSP System Toolbox)	single data type. Real values.	Filter structure: Direct-form II Transposed Coefficient sources: Property / Input port HasScaleValues: True / False Number of sections: 8 AND "FrameLength >= 9 (or) Number of sections>= 4 AND FrameLength >= 9	mw_qhdsp_iir_af

Note

Use only column-major layout for QHL/HVX replacements. For more information, see Row-Major and Column-Major Array Layouts.